Server : Apache
System : Linux server1.cgrithy.com 3.10.0-1160.95.1.el7.x86_64 #1 SMP Mon Jul 24 13:59:37 UTC 2023 x86_64
User : nobody ( 99)
PHP Version : 8.1.23
Disable Function : NONE
Directory : /usr/share/doc/mysql-connector-java-5.1.25/docs/
|
Server : Apache System : Linux server1.cgrithy.com 3.10.0-1160.95.1.el7.x86_64 #1 SMP Mon Jul 24 13:59:37 UTC 2023 x86_64 User : nobody ( 99) PHP Version : 8.1.23 Disable Function : NONE Directory : /usr/share/doc/mysql-connector-java-5.1.25/docs/ |
MySQL Connector/J Developer's Guide
Abstract
This manual describes how to install, configure, and develop
database applications using MySQL Connector/J, the JDBC driver for
communicating with MySQL servers.
For release notes detailing the changes in each release of
Connector/J, see MySQL Connector/J Release Notes
(http://dev.mysql.com/doc/relnotes/connector-j/en/).
Document generated on: 2013-04-16 (revision: 34916)
_______________________________________________________
Preface and Legal Notices
This manual describes how to install, configure, and develop
database applications using MySQL Connector/J, the JDBC driver for
communicating with MySQL servers.
Legal Notices
Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights
reserved.
This software and related documentation are provided under a
license agreement containing restrictions on use and disclosure
and are protected by intellectual property laws. Except as
expressly permitted in your license agreement or allowed by law,
you may not use, copy, reproduce, translate, broadcast, modify,
license, transmit, distribute, exhibit, perform, publish, or
display any part, in any form, or by any means. Reverse
engineering, disassembly, or decompilation of this software,
unless required by law for interoperability, is prohibited.
The information contained herein is subject to change without
notice and is not warranted to be error-free. If you find any
errors, please report them to us in writing.
If this software or related documentation is delivered to the U.S.
Government or anyone licensing it on behalf of the U.S.
Government, the following notice is applicable:
U.S. GOVERNMENT RIGHTS Programs, software, databases, and related
documentation and technical data delivered to U.S. Government
customers are "commercial computer software" or "commercial
technical data" pursuant to the applicable Federal Acquisition
Regulation and agency-specific supplemental regulations. As such,
the use, duplication, disclosure, modification, and adaptation
shall be subject to the restrictions and license terms set forth
in the applicable Government contract, and, to the extent
applicable by the terms of the Government contract, the additional
rights set forth in FAR 52.227-19, Commercial Computer Software
License (December 2007). Oracle USA, Inc., 500 Oracle Parkway,
Redwood City, CA 94065.
This software is developed for general use in a variety of
information management applications. It is not developed or
intended for use in any inherently dangerous applications,
including applications which may create a risk of personal injury.
If you use this software in dangerous applications, then you shall
be responsible to take all appropriate fail-safe, backup,
redundancy, and other measures to ensure the safe use of this
software. Oracle Corporation and its affiliates disclaim any
liability for any damages caused by use of this software in
dangerous applications.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. MySQL is a trademark of Oracle Corporation and/or its
affiliates, and shall not be used without Oracle's express written
authorization. Other names may be trademarks of their respective
owners.
This software and documentation may provide access to or
information on content, products, and services from third parties.
Oracle Corporation and its affiliates are not responsible for and
expressly disclaim all warranties of any kind with respect to
third-party content, products, and services. Oracle Corporation
and its affiliates will not be responsible for any loss, costs, or
damages incurred due to your access to or use of third-party
content, products, or services.
This document in any form, software or printed matter, contains
proprietary information that is the exclusive property of Oracle.
Your access to and use of this material is subject to the terms
and conditions of your Oracle Software License and Service
Agreement, which has been executed and with which you agree to
comply. This document and information contained herein may not be
disclosed, copied, reproduced, or distributed to anyone outside
Oracle without prior written consent of Oracle or as specifically
provided below. This document is not part of your license
agreement nor can it be incorporated into any contractual
agreement with Oracle or its subsidiaries or affiliates.
This documentation is NOT distributed under a GPL license. Use of
this documentation is subject to the following terms:
You may create a printed copy of this documentation solely for
your own personal use. Conversion to other formats is allowed as
long as the actual content is not altered or edited in any way.
You shall not publish or distribute this documentation in any form
or on any media, except if you distribute the documentation in a
manner similar to how Oracle disseminates it (that is,
electronically for download on a Web site with the software) or on
a CD-ROM or similar medium, provided however that the
documentation is disseminated together with the software on the
same medium. Any other use, such as any dissemination of printed
copies or use of this documentation, in whole or in part, in
another publication, requires the prior written consent from an
authorized representative of Oracle. Oracle and/or its affiliates
reserve any and all rights to this documentation not expressly
granted above.
For more information on the terms of this license, or for details
on how the MySQL documentation is built and produced, please visit
MySQL Contact & Questions (http://dev.mysql.com/contact/).
For additional licensing information, including licenses for
third-party libraries used by MySQL products, see "Preface and
Legal Notices."
For help with using MySQL, please visit either the MySQL Forums
(http://forums.mysql.com) or MySQL Mailing Lists
(http://lists.mysql.com) where you can discuss your issues with
other MySQL users.
For additional documentation on MySQL products, including
translations of the documentation into other languages, and
downloadable versions in variety of formats, including HTML and
PDF formats, see the MySQL Documentation Library
(http://dev.mysql.com/doc).
Chapter 1. MySQL Connector/J
This section explains how to configure and develop Java
applications with MySQL Connector/J, the JDBC driver that is
integrated with MySQL.
For release notes detailing the changes in each release of
Connector/J, see MySQL Connector/J Release Notes
(http://dev.mysql.com/doc/relnotes/connector-j/en/).
Chapter 2. Connector/J Versions
There are currently four versions of MySQL Connector/J available:
* Connector/J 5.1 is the Type 4 pure Java JDBC driver, which
conforms to the JDBC 3.0 and JDBC 4.0 specifications. It
provides compatibility with all the functionality of MySQL,
including 4.1, 5.0, 5.1, 5.4 and 5.5. Connector/J 5.1 provides
ease of development features, including auto-registration with
the Driver Manager, standardized validity checks, categorized
SQLExceptions, support for the JDBC-4.0 XML processing, per
connection client information, NCHAR
(http://dev.mysql.com/doc/refman/5.5/en/char.html), NVARCHAR
(http://dev.mysql.com/doc/refman/5.5/en/char.html) and NCLOB
types. This release also includes all bug fixes up to and
including Connector/J 5.0.6.
* Connector/J 5.0 provides support for all the functionality
offered by Connector/J 3.1 and includes distributed
transaction (XA) support.
* Connector/J 3.1 was designed for connectivity to MySQL 4.1 and
MySQL 5.0 servers and provides support for all the
functionality in MySQL 5.0 except distributed transaction (XA)
support.
* Connector/J 3.0 provides core functionality and was designed
for connectivity to MySQL 3.x or MySQL 4.1 servers, although
it provides basic compatibility with later versions of MySQL.
Connector/J 3.0 does not support server-side prepared
statements, and does not support any of the features in
versions of MySQL later than 4.1.
The following table summarizes the Connector/J versions available,
along with the details of JDBC driver type, what version of the
JDBC API it supports, what versions of MySQL Server it works with,
and whether it is currently supported or not:
Table 2.1. Summary of Connector/J Versions
Connector/J version Driver Type JDBC version MySQL Server version
Status
5.1 4 3.0, 4.0 4.1, 5.0, 5.1, 5.4, 5.5 Recommended version
5.0 4 3.0 4.1, 5.0 Released version
3.1 4 3.0 4.1, 5.0 Obsolete
3.0 4 3.0 3.x, 4.1 Obsolete
The current recommended version for Connector/J is 5.1. This guide
covers all four connector versions, with specific notes given
where a setting applies to a specific option.
2.1. Connector/J Release Notes and Change History
For details of new features and bug fixes in each Connector/J
release, see the MySQL Connector/J Release Notes
(http://dev.mysql.com/doc/relnotes/connector-j/en/).
2.2. Java Versions Supported
The following table summarizes what version of Java RTE is
required to use Connector/J with Java applications, and what
version of JDK is required to build Connector/J source code:
Table 2.2. Summary of Java Versions Required by Connector/J
Connector/J version Java RTE required JDK required (to build
source code)
5.1 1.5.x, 1.6.x, 1.7.x 1.6.x and 1.5.x
5.0 1.3.x, 1.4.x, 1.5.x, 1.6.x 1.4.2, 1.5.x, 1.6.x
3.1 1.2.x, 1.3.x, 1.4.x, 1.5.x, 1.6.x 1.4.2, 1.5.x, 1.6.x
3.0 1.2.x, 1.3.x, 1.4.x, 1.5.x, 1.6.x 1.4.2, 1.5.x, 1.6.x
If you are building Connector/J from source code using the source
distribution (see Section 3.4, "Installing from the Development
Source Tree"), you must use JDK 1.4.2 or newer to compile the
Connector package. For Connector/J 5.1, you must have both
JDK-1.6.x and JDK-1.5.x installed to be able to build the source
code.
Java 1.7 support requires Connector/J 5.1.21 and higher. Several
JDBC 4.1 methods were implemented for the first time in
Connector/J 5.1.21.
Because of the implementation of java.sql.Savepoint, Connector/J
3.1.0 and newer will not run on a Java runtime older than 1.4
unless the class verifier is turned off (by setting the
-Xverify:none option to the Java runtime). This is because the
class verifier will try to load the class definition for
java.sql.Savepoint even though it is not accessed by the driver
unless you actually use savepoint functionality.
Caching functionality provided by Connector/J 3.1.0 or newer is
also not available on JVMs older than 1.4.x, as it relies on
java.util.LinkedHashMap which was first available in JDK-1.4.0.
MySQL Connector/J does not support JDK-1.1.x or JDK-1.0.x.
Chapter 3. Connector/J Installation
You can install the Connector/J package using either the binary or
source distribution. The binary distribution provides the easiest
method for installation; the source distribution lets you
customize your installation further. With either solution, you
manually add the Connector/J location to your Java CLASSPATH.
If you are upgrading from a previous version, read the upgrade
information in Section 3.3, "Upgrading from an Older Version"
before continuing.
Connector/J is also available as part of the Maven project. For
more information, and to download the Connector/J JAR files, see
the Maven repository (http://www.ibiblio.org/maven/).
3.1. Installing Connector/J from a Binary Distribution
For the easiest method of installation, use the binary
distribution of the Connector/J package. The binary distribution
is available either as a tar/gzip or zip file. Extract it to a
suitable location, then optionally make the information about the
package available by changing your CLASSPATH (see Section 3.2,
"Installing the Driver and Configuring the CLASSPATH").
MySQL Connector/J is distributed as a .zip or .tar.gz archive
containing the sources, the class files, and the JAR archive named
mysql-connector-java-version-bin.jar.
Starting with Connector/J 3.1.9, the .class files that constitute
the JAR files are only included as part of the driver JAR file.
Starting with Connector/J 3.1.8, the archive also includes a debug
build of the driver in a file named
mysql-connector-java-version-bin-g.jar. Do not use the debug build
of the driver unless instructed to do so when reporting a problem
or a bug, as it is not designed to be run in production
environments, and will have adverse performance impact when used.
The debug binary also depends on the Aspect/J runtime library,
which is located in the src/lib/aspectjrt.jar file that comes with
the Connector/J distribution.
Use the appropriate graphical or command-line utility to extract
the distribution (for example, WinZip for the .zip archive, and
tar for the .tar.gz archive). Because there are potentially long
file names in the distribution, we use the GNU tar archive format.
Use GNU tar (or an application that understands the GNU tar
archive format) to unpack the .tar.gz variant of the distribution.
3.2. Installing the Driver and Configuring the CLASSPATH
Once you have extracted the distribution archive, you can install
the driver by placing mysql-connector-java-version-bin.jar in your
classpath, either by adding the full path to it to your CLASSPATH
environment variable, or by directly specifying it with the
command line switch -cp when starting the JVM.
To use the driver with the JDBC DriverManager, use
com.mysql.jdbc.Driver as the class that implements
java.sql.Driver.
You can set the CLASSPATH environment variable under UNIX, Linux
or Mac OS X either locally for a user within their .profile,
.login or other login file. You can also set it globally by
editing the global /etc/profile file.
For example, add the Connector/J driver to your CLASSPATH using
one of the following forms, depending on your command shell:
# Bourne-compatible shell (sh, ksh, bash, zsh):
shell> export CLASSPATH=/path/mysql-connector-java-ver-bin.jar:$CLASS
PATH
# C shell (csh, tcsh):
shell> setenv CLASSPATH /path/mysql-connector-java-ver-bin.jar:$CLASS
PATH
Within Windows 2000, Windows XP, Windows Server 2003 and Windows
Vista, you set the environment variable through the System Control
Panel.
To use MySQL Connector/J with an application server such as
GlassFish, Tomcat or JBoss, read your vendor's documentation for
more information on how to configure third-party class libraries,
as most application servers ignore the CLASSPATH environment
variable. For configuration examples for some J2EE application
servers, see Chapter 7, "Connection Pooling with Connector/J"
Chapter 8, "Load Balancing with Connector/J," and Chapter 9,
"Failover with Connector/J." However, the authoritative source for
JDBC connection pool configuration information for your particular
application server is the documentation for that application
server.
If you are developing servlets or JSPs, and your application
server is J2EE-compliant, you can put the driver's .jar file in
the WEB-INF/lib subdirectory of your webapp, as this is a standard
location for third party class libraries in J2EE web applications.
You can also use the MysqlDataSource or
MysqlConnectionPoolDataSource classes in the
com.mysql.jdbc.jdbc2.optional package, if your J2EE application
server supports or requires them. Starting with Connector/J 5.0.0,
the javax.sql.XADataSource interface is implemented using the
com.mysql.jdbc.jdbc2.optional.MysqlXADataSource class, which
supports XA distributed transactions when used in combination with
MySQL server version 5.0.
The various MysqlDataSource classes support the following
parameters (through standard set mutators):
* user
* password
* serverName (see the previous section about fail-over hosts)
* databaseName
* port
3.3. Upgrading from an Older Version
This section has information for users who are upgrading from one
version of Connector/J to another, or to a new version of the
MySQL server that supports a more recent level of JDBC. A newer
version of Connector/J might include changes to support new
features, improve existing functionality, or comply with new
standards.
3.3.1. Upgrading to MySQL Connector/J 5.1.x
* In Connector/J 5.0.x and earlier, the alias for a table in a
SELECT (http://dev.mysql.com/doc/refman/5.5/en/select.html)
statement is returned when accessing the result set metadata
using ResultSetMetaData.getColumnName(). This behavior however
is not JDBC compliant, and in Connector/J 5.1 this behavior
was changed so that the original table name, rather than the
alias, is returned.
The JDBC-compliant behavior is designed to let API users
reconstruct the DML statement based on the metadata within
ResultSet and ResultSetMetaData.
You can get the alias for a column in a result set by calling
ResultSetMetaData.getColumnLabel(). To use the old
noncompliant behavior with ResultSetMetaData.getColumnName(),
use the useOldAliasMetadataBehavior option and set the value
to true.
In Connector/J 5.0.x, the default value of
useOldAliasMetadataBehavior was true, but in Connector/J 5.1
this was changed to a default value of false.
3.3.2. JDBC-Specific Issues When Upgrading to MySQL Server 4.1 or
Newer
* Using the UTF-8 Character Encoding - Prior to MySQL server
version 4.1, the UTF-8 character encoding was not supported by
the server, however the JDBC driver could use it, allowing
storage of multiple character sets in latin1 tables on the
server.
Starting with MySQL-4.1, this functionality is deprecated. If
you have applications that rely on this functionality, and can
not upgrade them to use the official Unicode character support
in MySQL server version 4.1 or newer, add the following
property to your connection URL:
useOldUTF8Behavior=true
* Server-side Prepared Statements - Connector/J 3.1 will
automatically detect and use server-side prepared statements
when they are available (MySQL server version 4.1.0 and
newer). If your application encounters issues with server-side
prepared statements, you can revert to the older client-side
emulated prepared statement code that is still presently used
for MySQL servers older than 4.1.0 with the following
connection property:
useServerPrepStmts=false
3.3.3. Upgrading from MySQL Connector/J 3.0 to 3.1
Connector/J 3.1 is designed to be backward-compatible with
Connector/J 3.0 as much as possible. Major changes are isolated to
new functionality exposed in MySQL-4.1 and newer, which includes
Unicode character sets, server-side prepared statements, SQLState
codes returned in error messages by the server and various
performance enhancements that can be enabled or disabled using
configuration properties.
* Unicode Character Sets: See the next section, as well as
Character Set Support
(http://dev.mysql.com/doc/refman/5.5/en/charset.html), for
information on this MySQL feature. If you have something
misconfigured, it will usually show up as an error with a
message similar to Illegal mix of collations.
* Server-side Prepared Statements: Connector/J 3.1 will
automatically detect and use server-side prepared statements
when they are available (MySQL server version 4.1.0 and
newer).
Starting with version 3.1.7, the driver scans SQL you are
preparing using all variants of Connection.prepareStatement()
to determine if it is a supported type of statement to prepare
on the server side, and if it is not supported by the server,
it instead prepares it as a client-side emulated prepared
statement. You can disable this feature by passing
emulateUnsupportedPstmts=false in your JDBC URL.
If your application encounters issues with server-side
prepared statements, you can revert to the older client-side
emulated prepared statement code that is still presently used
for MySQL servers older than 4.1.0 with the connection
property useServerPrepStmts=false.
* Datetimes with all-zero components (0000-00-00 ...): These
values cannot be represented reliably in Java. Connector/J
3.0.x always converted them to NULL when being read from a
ResultSet.
Connector/J 3.1 throws an exception by default when these
values are encountered, as this is the most correct behavior
according to the JDBC and SQL standards. This behavior can be
modified using the zeroDateTimeBehavior configuration
property. The permissible values are:
+ exception (the default), which throws an SQLException
with an SQLState of S1009.
+ convertToNull, which returns NULL instead of the date.
+ round, which rounds the date to the nearest closest value
which is 0001-01-01.
Starting with Connector/J 3.1.7, ResultSet.getString() can be
decoupled from this behavior using noDatetimeStringSync=true
(the default value is false) so that you can retrieve the
unaltered all-zero value as a String. Note that this also
precludes using any time zone conversions, therefore the
driver will not allow you to enable noDatetimeStringSync and
useTimezone at the same time.
* New SQLState Codes: Connector/J 3.1 uses SQL:1999 SQLState
codes returned by the MySQL server (if supported), which are
different from the legacy X/Open state codes that Connector/J
3.0 uses. If connected to a MySQL server older than
MySQL-4.1.0 (the oldest version to return SQLStates as part of
the error code), the driver will use a built-in mapping. You
can revert to the old mapping by using the configuration
property useSqlStateCodes=false.
* ResultSet.getString(): Calling ResultSet.getString() on a BLOB
(http://dev.mysql.com/doc/refman/5.5/en/blob.html) column will
now return the address of the byte[] array that represents it,
instead of a String representation of the BLOB
(http://dev.mysql.com/doc/refman/5.5/en/blob.html). BLOB
(http://dev.mysql.com/doc/refman/5.5/en/blob.html) values have
no character set, so they cannot be converted to
java.lang.Strings without data loss or corruption.
To store strings in MySQL with LOB behavior, use one of the
TEXT (http://dev.mysql.com/doc/refman/5.5/en/blob.html) types,
which the driver will treat as a java.sql.Clob.
* Debug builds: Starting with Connector/J 3.1.8 a debug build of
the driver in a file named
mysql-connector-java-version-bin-g.jar is shipped alongside
the normal binary jar file that is named
mysql-connector-java-version-bin.jar.
Starting with Connector/J 3.1.9, we do not ship the .class
files unbundled, they are only available in the JAR archives
that ship with the driver.
Do not use the debug build of the driver unless instructed to
do so when reporting a problem or bug, as it is not designed
to be run in production environments, and will have adverse
performance impact when used. The debug binary also depends on
the Aspect/J runtime library, which is located in the
src/lib/aspectjrt.jar file that comes with the Connector/J
distribution.
3.4. Installing from the Development Source Tree
Caution
Read this section only if you are interested in helping us test
our new code. To just get MySQL Connector/J up and running on your
system, use a standard binary release distribution.
To install MySQL Connector/J from the development source tree,
make sure that you have the following prerequisites:
* A Bazaar client, to check out the sources from our Launchpad
repository (available from http://bazaar-vcs.org/).
* Apache Ant version 1.7 or newer (available from
http://ant.apache.org/).
* JDK 1.4.2 or later. Although MySQL Connector/J can be be used
with older JDKs, compiling it from source requires at least
JDK 1.4.2. To build Connector/J 5.1 requires JDK 1.6.x and an
older JDK such as JDK 1.5.x; point your JAVA_HOME environment
variable at the older installation.
To check out and compile a specific branch of MySQL Connector/J,
follow these steps:
1. Check out the latest code from the branch that you want with
one of the following commands.
The source code repository for MySQL Connector/J is located on
Launchpad at https://code.launchpad.net/connectorj. To check
out the latest development branch, use:
shell> bzr branch lp:connectorji
This creates a connectorj subdirectory in the current
directory that contains the latest sources for the requested
branch.
To check out the latest 5.1 code, use:
shell> bzr branch lp:connectorj/5.1
This creates a 5.1 subdirectory in the current directory
containing the latest 5.1 code.
2. To build Connector/J 5.1, make sure that you have both JDK
1.6.x installed and an older JDK such as JDK 1.5.x. This is
because Connector/J supports both JDBC 3.0 (which was prior to
JDK 1.6.x) and JDBC 4.0. Set your JAVA_HOME environment
variable to the path of the older JDK installation.
3. Change your current working directory to either the connectorj
or 5.1 directory, depending on which branch you intend to
build.
4. To build Connector/J 5.1, edit the build.xml to reflect the
location of your JDK 1.6.x installation. The lines to change
are:
<property name="com.mysql.jdbc.java6.javac" value="C:\jvm
s\jdk1.6.0\bin\javac.exe" />
<property name="com.mysql.jdbc.java6.rtjar" value="C:\jvm
s\jdk1.6.0\jre\lib\rt.jar" />
Alternatively, you can set the value of these property names
through the Ant -D option.
5. Issue the following command to compile the driver and create a
.jar file suitable for installation:
shell> ant dist
This creates a build directory in the current directory, where
all build output will go. A directory is created in the build
directory that includes the version number of the sources you
are building from. This directory contains the sources,
compiled .class files, and a .jar file suitable for
deployment. For other possible targets, including ones that
will create a fully packaged distribution, issue the following
command:
shell> ant -projecthelp
6. A newly created .jar file containing the JDBC driver will be
placed in the directory build/mysql-connector-java-version.
Install the newly created JDBC driver as you would a binary
.jar file that you download from MySQL, by following the
instructions in Section 3.2, "Installing the Driver and
Configuring the CLASSPATH."
A package containing both the binary and source code for
Connector/J 5.1 can also be found at the following location:
Connector/J 5.1 Download
(http://dev.mysql.com/downloads/connector/j/5.1.html)
Chapter 4. Connector/J Examples
Examples of using Connector/J are located throughout this
document. This section provides a summary and links to these
examples.
* Example 6.1, "Connector/J: Obtaining a connection from the
DriverManager"
* Example 6.2, "Connector/J: Using java.sql.Statement to execute
a SELECT query"
* Example 6.3, "Connector/J: Calling Stored Procedures"
* Example 6.3, "Connector/J: Using Connection.prepareCall()"
* Example 6.3, "Connector/J: Registering output parameters"
* Example 6.3, "Connector/J: Setting CallableStatement input
parameters"
* Example 6.3, "Connector/J: Retrieving results and output
parameter values"
* Example 6.4, "Connector/J: Retrieving AUTO_INCREMENT column
values using Statement.getGeneratedKeys()"
* Example 6.4, "Connector/J: Retrieving AUTO_INCREMENT column
values using SELECT LAST_INSERT_ID()"
* Example 6.4, "Connector/J: Retrieving AUTO_INCREMENT column
values in Updatable ResultSets"
* Example 7, "Connector/J: Using a connection pool with a J2EE
application server"
* Example 15, "Connector/J: Example of transaction with retry
logic"
Chapter 5. Connector/J (JDBC) Reference
This section of the manual contains reference material for MySQL
Connector/J.
5.1. Driver/Datasource Class Names, URL Syntax and Configuration
Properties for Connector/J
The name of the class that implements java.sql.Driver in MySQL
Connector/J is com.mysql.jdbc.Driver. The org.gjt.mm.mysql.Driver
class name is also usable for backward compatibility with
MM.MySQL, the predecessor of Connector/J. Use this class name when
registering the driver, or when otherwise configuring software to
use MySQL Connector/J.
JDBC URL Format
The JDBC URL format for MySQL Connector/J is as follows, with
items in square brackets ([, ]) being optional:
jdbc:mysql://[host][,failoverhost...][:port]/[database] ??
[?propertyName1][=propertyValue1][&propertyName2][=propertyValue2]...
If the host name is not specified, it defaults to 127.0.0.1. If
the port is not specified, it defaults to 3306, the default port
number for MySQL servers.
jdbc:mysql://[host:port],[host:port].../[database] ??
[?propertyName1][=propertyValue1][&propertyName2][=propertyValue2]...
Here is a sample connection URL:
jdbc:mysql://localhost:3306/sakila?profileSQL=true
IPv6 Connections
For IPv6 connections, use this alternative syntax to specify hosts
in the URL, address=(key=value). Supported keys are:
* (protocol=tcp), or (protocol=pipe) for named pipes on Windows.
* (path=path_to_pipe) for named pipes.
* (host=hostname) for TCP connections.
* (port=port_number) for TCP connections.
For example:
jdbc:mysql://address=(protocol=tcp)(host=localhost)(port=3306)(user=t
est)/db
Any other parameters are treated as host-specific properties that
follow the conventions of the JDBC URL properties. This now allows
per-host overrides of any configuration property for multi-host
connections (that is, when using failover, load balancing, or
replication). Limit the overrides to user, password, network
timeouts and statement and metadata cache sizes; the results of
other per-host overrides are not defined.
Initial Database for Connection
If the database is not specified, the connection is made with no
default database. In this case, either call the setCatalog()
method on the Connection instance, or fully specify table names
using the database name (that is, SELECT dbname.tablename.colname
FROM dbname.tablename...) in your SQL. Opening a connection
without specifying the database to use is generally only useful
when building tools that work with multiple databases, such as GUI
database managers.
Note
Always use the Connection.setCatalog() method to specify the
desired database in JDBC applications, rather than the USE
database statement.
Failover Support
MySQL Connector/J has failover support. This enables the driver to
fail over to any number of slave hosts and still perform read-only
queries. Failover only happens when the connection is in an
autoCommit(true) state, because failover cannot happen reliably
when a transaction
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_transac
tion) is in progress. Most application servers and connection
pools set autoCommit to true at the end of every
transaction/connection use.
The failover functionality has the following behavior:
* If the URL property autoReconnect is false: Failover only
happens at connection initialization, and failback occurs when
the driver determines that the first host has become available
again.
* If the URL property autoReconnect is true: Failover happens
when the driver determines that the connection has failed
(checked before every query), and falls back to the first host
when it determines that the host has become available again
(after queriesBeforeRetryMaster queries have been issued).
In either case, whenever you are connected to a "failed-over"
server, the connection is set to read-only state, so queries that
attempt to modify data will throw exceptions (the query will never
be processed by the MySQL server).
Setting Configuration Properties
Configuration properties define how Connector/J will make a
connection to a MySQL server. Unless otherwise noted, properties
can be set for a DataSource object or for a Connection object.
Configuration properties can be set in one of the following ways:
* Using the set*() methods on MySQL implementations of
java.sql.DataSource (which is the preferred method when using
implementations of java.sql.DataSource):
+ com.mysql.jdbc.jdbc2.optional.MysqlDataSource
+ com.mysql.jdbc.jdbc2.optional.MysqlConnectionPoolDataSour
ce
* As a key/value pair in the java.util.Properties instance
passed to DriverManager.getConnection() or Driver.connect()
* As a JDBC URL parameter in the URL given to
java.sql.DriverManager.getConnection(),
java.sql.Driver.connect() or the MySQL implementations of the
javax.sql.DataSource setURL() method.
Note
If the mechanism you use to configure a JDBC URL is XML-based,
use the XML character literal & to separate configuration
parameters, as the ampersand is a reserved character for XML.
The properties are listed in the following tables.
Connection/Authentication.
Property Name Definition Default Value Since Version
user The user to connect as all versions
password The password to use when connecting all versions
socketFactory The name of the class that the driver should use for
creating socket connections to the server. This class must
implement the interface 'com.mysql.jdbc.SocketFactory' and have
public no-args constructor. com.mysql.jdbc.StandardSocketFactory
3.0.3
connectTimeout Timeout for socket connect (in milliseconds), with
0 being no timeout. Only works on JDK-1.4 or newer. Defaults to
'0'. 0 3.0.1
socketTimeout Timeout on network socket operations (0, the default
means no timeout). 0 3.0.1
connectionLifecycleInterceptors A comma-delimited list of classes
that implement "com.mysql.jdbc.ConnectionLifecycleInterceptor"
that should notified of connection lifecycle events (creation,
destruction, commit, rollback, setCatalog and setAutoCommit) and
potentially alter the execution of these commands.
ConnectionLifecycleInterceptors are "stackable", more than one
interceptor may be specified via the configuration property as a
comma-delimited list, with the interceptors executed in order from
left to right. 5.1.4
useConfigs Load the comma-delimited list of configuration
properties before parsing the URL or applying user-specified
properties. These configurations are explained in the
'Configurations' of the documentation. 3.1.5
authenticationPlugins Comma-delimited list of classes that
implement com.mysql.jdbc.AuthenticationPlugin and which will be
used for authentication unless disabled by
"disabledAuthenticationPlugins" property. 5.1.19
defaultAuthenticationPlugin Name of a class implementing
com.mysql.jdbc.AuthenticationPlugin which will be used as the
default authentication plugin (see below). It is an error to use a
class which is not listed in "authenticationPlugins" nor it is one
of the built-in plugins. It is an error to set as default a plugin
which was disabled with "disabledAuthenticationPlugins" property.
It is an error to set this value to null or the empty string (i.e.
there must be at least a valid default authentication plugin
specified for the connection, meeting all constraints listed
above). com.mysql.jdbc.authentication.MysqlNativePasswordPlugin
5.1.19
disabledAuthenticationPlugins Comma-delimited list of classes
implementing com.mysql.jdbc.AuthenticationPlugin or mechanisms,
i.e. "mysql_native_password". The authentication plugins or
mechanisms listed will not be used for authentication which will
fail if it requires one of them. It is an error to disable the
default authentication plugin (either the one named by
"defaultAuthenticationPlugin" property or the hard-coded one if
"defaultAuthenticationPlugin" property is not set). 5.1.19
disconnectOnExpiredPasswords If "disconnectOnExpiredPasswords" is
set to "false" and password is expired then server enters
"sandbox" mode and sends ERR(08001, ER_MUST_CHANGE_PASSWORD) for
all commands that are not needed to set a new password until a new
password is set. true 5.1.23
interactiveClient Set the CLIENT_INTERACTIVE flag, which tells
MySQL to timeout connections based on INTERACTIVE_TIMEOUT instead
of WAIT_TIMEOUT false 3.1.0
localSocketAddress Hostname or IP address given to explicitly
configure the interface that the driver will bind the client side
of the TCP/IP connection to when connecting. 5.0.5
propertiesTransform An implementation of
com.mysql.jdbc.ConnectionPropertiesTransform that the driver will
use to modify URL properties passed to the driver before
attempting a connection 3.1.4
useCompression Use zlib compression when communicating with the
server (true/false)? Defaults to 'false'. false 3.0.17
Networking.
Property Name Definition Default Value Since Version
maxAllowedPacket Maximum allowed packet size to send to server. If
not set, the value of system variable 'max_allowed_packet' will be
used to initialize this upon connecting. This value will not take
effect if set larger than the value of 'max_allowed_packet'. -1
5.1.8
tcpKeepAlive If connecting using TCP/IP, should the driver set
SO_KEEPALIVE? true 5.0.7
tcpNoDelay If connecting using TCP/IP, should the driver set
SO_TCP_NODELAY (disabling the Nagle Algorithm)? true 5.0.7
tcpRcvBuf If connecting using TCP/IP, should the driver set
SO_RCV_BUF to the given value? The default value of '0', means use
the platform default value for this property) 0 5.0.7
tcpSndBuf If connecting using TCP/IP, should the driver set
SO_SND_BUF to the given value? The default value of '0', means use
the platform default value for this property) 0 5.0.7
tcpTrafficClass If connecting using TCP/IP, should the driver set
traffic class or type-of-service fields ?See the documentation for
java.net.Socket.setTrafficClass() for more information. 0 5.0.7
High Availability and Clustering.
Property Name Definition Default Value Since Version
autoReconnect Should the driver try to re-establish stale and/or
dead connections? If enabled the driver will throw an exception
for a queries issued on a stale or dead connection, which belong
to the current transaction, but will attempt reconnect before the
next query issued on the connection in a new transaction. The use
of this feature is not recommended, because it has side effects
related to session state and data consistency when applications
don't handle SQLExceptions properly, and is only designed to be
used when you are unable to configure your application to handle
SQLExceptions resulting from dead and stale connections properly.
Alternatively, as a last option, investigate setting the MySQL
server variable "wait_timeout" to a high value, rather than the
default of 8 hours. false 1.1
autoReconnectForPools Use a reconnection strategy appropriate for
connection pools (defaults to 'false') false 3.1.3
failOverReadOnly When failing over in autoReconnect mode, should
the connection be set to 'read-only'? true 3.0.12
maxReconnects Maximum number of reconnects to attempt if
autoReconnect is true, default is '3'. 3 1.1
reconnectAtTxEnd If autoReconnect is set to true, should the
driver attempt reconnections at the end of every transaction?
false 3.0.10
retriesAllDown When using loadbalancing, the number of times the
driver should cycle through available hosts, attempting to
connect. Between cycles, the driver will pause for 250ms if no
servers are available. 120 5.1.6
initialTimeout If autoReconnect is enabled, the initial time to
wait between re-connect attempts (in seconds, defaults to '2'). 2
1.1
roundRobinLoadBalance When autoReconnect is enabled, and
failoverReadonly is false, should we pick hosts to connect to on a
round-robin basis? false 3.1.2
queriesBeforeRetryMaster Number of queries to issue before falling
back to master when failed over (when using multi-host failover).
Whichever condition is met first, 'queriesBeforeRetryMaster' or
'secondsBeforeRetryMaster' will cause an attempt to be made to
reconnect to the master. Defaults to 50. 50 3.0.2
secondsBeforeRetryMaster How long should the driver wait, when
failed over, before attempting 30 3.0.2
selfDestructOnPingMaxOperations =If set to a non-zero value, the
driver will report close the connection and report failure when
Connection.ping() or Connection.isValid(int) is called if the
connection's count of commands sent to the server exceeds this
value. 0 5.1.6
selfDestructOnPingSecondsLifetime If set to a non-zero value, the
driver will report close the connection and report failure when
Connection.ping() or Connection.isValid(int) is called if the
connection's lifetime exceeds this value. 0 5.1.6
resourceId A globally unique name that identifies the resource
that this datasource or connection is connected to, used for
XAResource.isSameRM() when the driver can't determine this value
based on hostnames used in the URL 5.0.1
Security.
Property Name Definition Default Value Since Version
allowMultiQueries Allow the use of ';' to delimit multiple queries
during one statement (true/false), defaults to 'false', and does
not affect the addBatch() and executeBatch() methods, which
instead rely on rewriteBatchStatements. false 3.1.1
useSSL Use SSL when communicating with the server (true/false),
defaults to 'false' false 3.0.2
requireSSL Require SSL connection if useSSL=true? (defaults to
'false'). false 3.1.0
verifyServerCertificate If "useSSL" is set to "true", should the
driver verify the server's certificate? When using this feature,
the keystore parameters should be specified by the
"clientCertificateKeyStore*" properties, rather than system
properties. true 5.1.6
clientCertificateKeyStoreUrl URL to the client certificate
KeyStore (if not specified, use defaults) 5.1.0
clientCertificateKeyStoreType KeyStore type for client
certificates (NULL or empty means use the default, which is "JKS".
Standard keystore types supported by the JVM are "JKS" and
"PKCS12", your environment may have more available depending on
what security products are installed and available to the JVM. JKS
5.1.0
clientCertificateKeyStorePassword Password for the client
certificates KeyStore 5.1.0
trustCertificateKeyStoreUrl URL to the trusted root certificate
KeyStore (if not specified, use defaults) 5.1.0
trustCertificateKeyStoreType KeyStore type for trusted root
certificates (NULL or empty means use the default, which is "JKS".
Standard keystore types supported by the JVM are "JKS" and
"PKCS12", your environment may have more available depending on
what security products are installed and available to the JVM. JKS
5.1.0
trustCertificateKeyStorePassword Password for the trusted root
certificates KeyStore 5.1.0
allowLoadLocalInfile Should the driver allow use of 'LOAD DATA
LOCAL INFILE...' (defaults to 'true'). true 3.0.3
allowUrlInLocalInfile Should the driver allow URLs in 'LOAD DATA
LOCAL INFILE' statements? false 3.1.4
paranoid Take measures to prevent exposure sensitive information
in error messages and clear data structures holding sensitive data
when possible? (defaults to 'false') false 3.0.1
passwordCharacterEncoding What character encoding is used for
passwords? Leaving this set to the default value (null), uses the
platform character set, which works for ISO8859_1 (i.e. "latin1")
passwords. For passwords in other character encodings, the
encoding will have to be specified with this property, as it's not
possible for the driver to auto-detect this. 5.1.7
Performance Extensions.
Property Name Definition Default Value Since Version
callableStmtCacheSize If 'cacheCallableStmts' is enabled, how many
callable statements should be cached? 100 3.1.2
metadataCacheSize The number of queries to cache ResultSetMetadata
for if cacheResultSetMetaData is set to 'true' (default 50) 50
3.1.1
useLocalSessionState Should the driver refer to the internal
values of autocommit and transaction isolation that are set by
Connection.setAutoCommit() and
Connection.setTransactionIsolation() and transaction state as
maintained by the protocol, rather than querying the database or
blindly sending commands to the database for commit() or
rollback() method calls? false 3.1.7
useLocalTransactionState Should the driver use the in-transaction
state provided by the MySQL protocol to determine if a commit() or
rollback() should actually be sent to the database? false 5.1.7
prepStmtCacheSize If prepared statement caching is enabled, how
many prepared statements should be cached? 25 3.0.10
prepStmtCacheSqlLimit If prepared statement caching is enabled,
what's the largest SQL the driver will cache the parsing for? 256
3.0.10
parseInfoCacheFactory Name of a class implementing
com.mysql.jdbc.CacheAdapterFactory, which will be used to create
caches for the parsed representation of client-side prepared
statements. com.mysql.jdbc.PerConnectionLRUFactory 5.1.1
serverConfigCacheFactory Name of a class implementing
com.mysql.jdbc.CacheAdapterFactory<String, Map<String, String>>,
which will be used to create caches for MySQL server configuration
values com.mysql.jdbc.PerVmServerConfigCacheFactory 5.1.1
alwaysSendSetIsolation Should the driver always communicate with
the database when Connection.setTransactionIsolation() is called?
If set to false, the driver will only communicate with the
database when the requested transaction isolation is different
than the whichever is newer, the last value that was set via
Connection.setTransactionIsolation(), or the value that was read
from the server when the connection was established. Note that
useLocalSessionState=true will force the same behavior as
alwaysSendSetIsolation=false, regardless of how
alwaysSendSetIsolation is set. true 3.1.7
maintainTimeStats Should the driver maintain various internal
timers to enable idle time calculations as well as more verbose
error messages when the connection to the server fails? Setting
this property to false removes at least two calls to
System.getCurrentTimeMillis() per query. true 3.1.9
useCursorFetch If connected to MySQL > 5.0.2, and setFetchSize() >
0 on a statement, should that statement use cursor-based fetching
to retrieve rows? false 5.0.0
blobSendChunkSize Chunk to use when sending BLOB/CLOBs via
ServerPreparedStatements 1048576 3.1.9
cacheCallableStmts Should the driver cache the parsing stage of
CallableStatements false 3.1.2
cachePrepStmts Should the driver cache the parsing stage of
PreparedStatements of client-side prepared statements, the "check"
for suitability of server-side prepared and server-side prepared
statements themselves? false 3.0.10
cacheResultSetMetadata Should the driver cache ResultSetMetaData
for Statements and PreparedStatements? (Req. JDK-1.4+, true/false,
default 'false') false 3.1.1
cacheServerConfiguration Should the driver cache the results of
'SHOW VARIABLES' and 'SHOW COLLATION' on a per-URL basis? false
3.1.5
defaultFetchSize The driver will call setFetchSize(n) with this
value on all newly-created Statements 0 3.1.9
dontTrackOpenResources The JDBC specification requires the driver
to automatically track and close resources, however if your
application doesn't do a good job of explicitly calling close() on
statements or result sets, this can cause memory leakage. Setting
this property to true relaxes this constraint, and can be more
memory efficient for some applications. false 3.1.7
dynamicCalendars Should the driver retrieve the default calendar
when required, or cache it per connection/session? false 3.1.5
elideSetAutoCommits If using MySQL-4.1 or newer, should the driver
only issue 'set autocommit=n' queries when the server's state
doesn't match the requested state by
Connection.setAutoCommit(boolean)? false 3.1.3
enableQueryTimeouts When enabled, query timeouts set via
Statement.setQueryTimeout() use a shared java.util.Timer instance
for scheduling. Even if the timeout doesn't expire before the
query is processed, there will be memory used by the TimerTask for
the given timeout which won't be reclaimed until the time the
timeout would have expired if it hadn't been cancelled by the
driver. High-load environments might want to consider disabling
this functionality. true 5.0.6
holdResultsOpenOverStatementClose Should the driver close result
sets on Statement.close() as required by the JDBC specification?
false 3.1.7
largeRowSizeThreshold What size result set row should the JDBC
driver consider "large", and thus use a more memory-efficient way
of representing the row internally? 2048 5.1.1
loadBalanceStrategy If using a load-balanced connection to connect
to SQL nodes in a MySQL Cluster/NDB configuration (by using the
URL prefix "jdbc:mysql:loadbalance://"), which load balancing
algorithm should the driver use: (1) "random" - the driver will
pick a random host for each request. This tends to work better
than round-robin, as the randomness will somewhat account for
spreading loads where requests vary in response time, while
round-robin can sometimes lead to overloaded nodes if there are
variations in response times across the workload. (2)
"bestResponseTime" - the driver will route the request to the host
that had the best response time for the previous transaction.
random 5.0.6
locatorFetchBufferSize If 'emulateLocators' is configured to
'true', what size buffer should be used when fetching BLOB data
for getBinaryInputStream? 1048576 3.2.1
rewriteBatchedStatements Should the driver use multiqueries
(irregardless of the setting of "allowMultiQueries") as well as
rewriting of prepared statements for INSERT into multi-value
inserts when executeBatch() is called? Notice that this has the
potential for SQL injection if using plain java.sql.Statements and
your code doesn't sanitize input correctly. Notice that for
prepared statements, server-side prepared statements can not
currently take advantage of this rewrite option, and that if you
don't specify stream lengths when using
PreparedStatement.set*Stream(), the driver won't be able to
determine the optimum number of parameters per batch and you might
receive an error from the driver that the resultant packet is too
large. Statement.getGeneratedKeys() for these rewritten statements
only works when the entire batch includes INSERT statements. false
3.1.13
useDirectRowUnpack Use newer result set row unpacking code that
skips a copy from network buffers to a MySQL packet instance and
instead reads directly into the result set row data buffers. true
5.1.1
useDynamicCharsetInfo Should the driver use a per-connection cache
of character set information queried from the server when
necessary, or use a built-in static mapping that is more
efficient, but isn't aware of custom character sets or character
sets implemented after the release of the JDBC driver? true 5.0.6
useFastDateParsing Use internal String->Date/Time/Timestamp
conversion routines to avoid excessive object creation? true 5.0.5
useFastIntParsing Use internal String->Integer conversion routines
to avoid excessive object creation? true 3.1.4
useJvmCharsetConverters Always use the character encoding routines
built into the JVM, rather than using lookup tables for
single-byte character sets? false 5.0.1
useReadAheadInput Use newer, optimized non-blocking, buffered
input stream when reading from the server? true 3.1.5
Debugging/Profiling.
Property Name Definition Default Value Since Version
logger The name of a class that implements
"com.mysql.jdbc.log.Log" that will be used to log messages to.
(default is "com.mysql.jdbc.log.StandardLogger", which logs to
STDERR) com.mysql.jdbc.log.StandardLogger 3.1.1
gatherPerfMetrics Should the driver gather performance metrics,
and report them via the configured logger every
'reportMetricsIntervalMillis' milliseconds? false 3.1.2
profileSQL Trace queries and their execution/fetch times to the
configured logger (true/false) defaults to 'false' false 3.1.0
profileSql Deprecated, use 'profileSQL' instead. Trace queries and
their execution/fetch times on STDERR (true/false) defaults to
'false' 2.0.14
reportMetricsIntervalMillis If 'gatherPerfMetrics' is enabled, how
often should they be logged (in ms)? 30000 3.1.2
maxQuerySizeToLog Controls the maximum length/size of a query that
will get logged when profiling or tracing 2048 3.1.3
packetDebugBufferSize The maximum number of packets to retain when
'enablePacketDebug' is true 20 3.1.3
slowQueryThresholdMillis If 'logSlowQueries' is enabled, how long
should a query (in ms) before it is logged as 'slow'? 2000 3.1.2
slowQueryThresholdNanos If 'useNanosForElapsedTime' is set to
true, and this property is set to a non-zero value, the driver
will use this threshold (in nanosecond units) to determine if a
query was slow. 0 5.0.7
useUsageAdvisor Should the driver issue 'usage' warnings advising
proper and efficient usage of JDBC and MySQL Connector/J to the
log (true/false, defaults to 'false')? false 3.1.1
autoGenerateTestcaseScript Should the driver dump the SQL it is
executing, including server-side prepared statements to STDERR?
false 3.1.9
autoSlowLog Instead of using slowQueryThreshold* to determine if a
query is slow enough to be logged, maintain statistics that allow
the driver to determine queries that are outside the 99th
percentile? true 5.1.4
clientInfoProvider The name of a class that implements the
com.mysql.jdbc.JDBC4ClientInfoProvider interface in order to
support JDBC-4.0's Connection.get/setClientInfo() methods
com.mysql.jdbc.JDBC4CommentClientInfoProvider 5.1.0
dumpMetadataOnColumnNotFound Should the driver dump the
field-level metadata of a result set into the exception message
when ResultSet.findColumn() fails? false 3.1.13
dumpQueriesOnException Should the driver dump the contents of the
query sent to the server in the message for SQLExceptions? false
3.1.3
enablePacketDebug When enabled, a ring-buffer of
'packetDebugBufferSize' packets will be kept, and dumped when
exceptions are thrown in key areas in the driver's code false
3.1.3
explainSlowQueries If 'logSlowQueries' is enabled, should the
driver automatically issue an 'EXPLAIN' on the server and send the
results to the configured log at a WARN level? false 3.1.2
includeInnodbStatusInDeadlockExceptions Include the output of
"SHOW ENGINE INNODB STATUS" in exception messages when deadlock
exceptions are detected? false 5.0.7
includeThreadDumpInDeadlockExceptions Include a current Java
thread dump in exception messages when deadlock exceptions are
detected? false 5.1.15
includeThreadNamesAsStatementComment Include the name of the
current thread as a comment visible in "SHOW PROCESSLIST", or in
Innodb deadlock dumps, useful in correlation with
"includeInnodbStatusInDeadlockExceptions=true" and
"includeThreadDumpInDeadlockExceptions=true". false 5.1.15
logSlowQueries Should queries that take longer than
'slowQueryThresholdMillis' be logged? false 3.1.2
logXaCommands Should the driver log XA commands sent by
MysqlXaConnection to the server, at the DEBUG level of logging?
false 5.0.5
profilerEventHandler Name of a class that implements the interface
com.mysql.jdbc.profiler.ProfilerEventHandler that will be used to
handle profiling/tracing events.
com.mysql.jdbc.profiler.LoggingProfilerEventHandler 5.1.6
resultSetSizeThreshold If the usage advisor is enabled, how many
rows should a result set contain before the driver warns that it
is suspiciously large? 100 5.0.5
traceProtocol Should trace-level network protocol be logged? false
3.1.2
useNanosForElapsedTime For profiling/debugging functionality that
measures elapsed time, should the driver try to use nanoseconds
resolution if available (JDK >= 1.5)? false 5.0.7
Miscellaneous.
Property Name Definition Default Value Since Version
useUnicode Should the driver use Unicode character encodings when
handling strings? Should only be used when the driver can't
determine the character set mapping, or you are trying to 'force'
the driver to use a character set that MySQL either doesn't
natively support (such as UTF-8), true/false, defaults to 'true'
true 1.1g
characterEncoding If 'useUnicode' is set to true, what character
encoding should the driver use when dealing with strings?
(defaults is to 'autodetect') 1.1g
characterSetResults Character set to tell the server to return
results as. 3.0.13
connectionAttributes A comma-delimited list of user-defined
key:value pairs (in addition to standard MySQL-defined key:value
pairs) to be passed to MySQL Server for display as connection
attributes in the PERFORMANCE_SCHEMA.SESSION_CONNECT_ATTRS table.
Example usage: connectionAttributes=key1:value1,key2:value2 This
functionality is available for use with MySQL Server version 5.6
or later only. Earlier versions of MySQL Server do not support
connection attributes, causing this configuration option will be
ignored. Setting connectionAttributes=none will cause connection
attribute processing to be bypassed, for situations where
Connection creation/initialization speed is critical. 5.1.25
connectionCollation If set, tells the server to use this collation
via 'set collation_connection' 3.0.13
useBlobToStoreUTF8OutsideBMP Tells the driver to treat
[MEDIUM/LONG]BLOB columns as [LONG]VARCHAR columns holding text
encoded in UTF-8 that has characters outside the BMP (4-byte
encodings), which MySQL server can't handle natively. false 5.1.3
utf8OutsideBmpExcludedColumnNamePattern When
"useBlobToStoreUTF8OutsideBMP" is set to "true", column names
matching the given regex will still be treated as BLOBs unless
they match the regex specified for
"utf8OutsideBmpIncludedColumnNamePattern". The regex must follow
the patterns used for the java.util.regex package. 5.1.3
utf8OutsideBmpIncludedColumnNamePattern Used to specify exclusion
rules to "utf8OutsideBmpExcludedColumnNamePattern". The regex must
follow the patterns used for the java.util.regex package. 5.1.3
loadBalanceEnableJMX Enables JMX-based management of load-balanced
connection groups, including live addition/removal of hosts from
load-balancing pool. false 5.1.13
sessionVariables A comma-separated list of name/value pairs to be
sent as SET SESSION ... to the server when the driver connects.
3.1.8
useColumnNamesInFindColumn Prior to JDBC-4.0, the JDBC
specification had a bug related to what could be given as a
"column name" to ResultSet methods like findColumn(), or getters
that took a String property. JDBC-4.0 clarified "column name" to
mean the label, as given in an "AS" clause and returned by
ResultSetMetaData.getColumnLabel(), and if no AS clause, the
column name. Setting this property to "true" will give behavior
that is congruent to JDBC-3.0 and earlier versions of the JDBC
specification, but which because of the specification bug could
give unexpected results. This property is preferred over
"useOldAliasMetadataBehavior" unless you need the specific
behavior that it provides with respect to ResultSetMetadata. false
5.1.7
allowNanAndInf Should the driver allow NaN or +/- INF values in
PreparedStatement.setDouble()? false 3.1.5
autoClosePStmtStreams Should the driver automatically call
.close() on streams/readers passed as arguments via set*()
methods? false 3.1.12
autoDeserialize Should the driver automatically detect and
de-serialize objects stored in BLOB fields? false 3.1.5
blobsAreStrings Should the driver always treat BLOBs as Strings -
specifically to work around dubious metadata returned by the
server for GROUP BY clauses? false 5.0.8
capitalizeTypeNames Capitalize type names in DatabaseMetaData?
(usually only useful when using WebObjects, true/false, defaults
to 'false') true 2.0.7
clobCharacterEncoding The character encoding to use for sending
and retrieving TEXT, MEDIUMTEXT and LONGTEXT values instead of the
configured connection characterEncoding 5.0.0
clobberStreamingResults This will cause a 'streaming' ResultSet to
be automatically closed, and any outstanding data still streaming
from the server to be discarded if another query is executed
before all the data has been read from the server. false 3.0.9
compensateOnDuplicateKeyUpdateCounts Should the driver compensate
for the update counts of "ON DUPLICATE KEY" INSERT statements (2 =
1, 0 = 1) when using prepared statements? false 5.1.7
continueBatchOnError Should the driver continue processing batch
commands if one statement fails. The JDBC spec allows either way
(defaults to 'true'). true 3.0.3
createDatabaseIfNotExist Creates the database given in the URL if
it doesn't yet exist. Assumes the configured user has permissions
to create databases. false 3.1.9
emptyStringsConvertToZero Should the driver allow conversions from
empty string fields to numeric values of '0'? true 3.1.8
emulateLocators Should the driver emulate java.sql.Blobs with
locators? With this feature enabled, the driver will delay loading
the actual Blob data until the one of the retrieval methods
(getInputStream(), getBytes(), and so forth) on the blob data
stream has been accessed. For this to work, you must use a column
alias with the value of the column to the actual name of the Blob.
The feature also has the following restrictions: The SELECT that
created the result set must reference only one table, the table
must have a primary key; the SELECT must alias the original blob
column name, specified as a string, to an alternate name; the
SELECT must cover all columns that make up the primary key. false
3.1.0
emulateUnsupportedPstmts Should the driver detect prepared
statements that are not supported by the server, and replace them
with client-side emulated versions? true 3.1.7
exceptionInterceptors Comma-delimited list of classes that
implement com.mysql.jdbc.ExceptionInterceptor. These classes will
be instantiated one per Connection instance, and all SQLExceptions
thrown by the driver will be allowed to be intercepted by these
interceptors, in a chained fashion, with the first class listed as
the head of the chain. 5.1.8
functionsNeverReturnBlobs Should the driver always treat data from
functions returning BLOBs as Strings - specifically to work around
dubious metadata returned by the server for GROUP BY clauses?
false 5.0.8
generateSimpleParameterMetadata Should the driver generate
simplified parameter metadata for PreparedStatements when no
metadata is available either because the server couldn't support
preparing the statement, or server-side prepared statements are
disabled? false 5.0.5
ignoreNonTxTables Ignore non-transactional table warning for
rollback? (defaults to 'false'). false 3.0.9
jdbcCompliantTruncation Should the driver throw
java.sql.DataTruncation exceptions when data is truncated as is
required by the JDBC specification when connected to a server that
supports warnings (MySQL 4.1.0 and newer)? This property has no
effect if the server sql-mode includes STRICT_TRANS_TABLES. true
3.1.2
loadBalanceAutoCommitStatementRegex When load-balancing is enabled
for auto-commit statements (via
loadBalanceAutoCommitStatementThreshold), the statement counter
will only increment when the SQL matches the regular expression.
By default, every statement issued matches. 5.1.15
loadBalanceAutoCommitStatementThreshold When auto-commit is
enabled, the number of statements which should be executed before
triggering load-balancing to rebalance. Default value of 0 causes
load-balanced connections to only rebalance when exceptions are
encountered, or auto-commit is disabled and transactions are
explicitly committed or rolled back. 0 5.1.15
loadBalanceBlacklistTimeout Time in milliseconds between checks of
servers which are unavailable, by controlling how long a server
lives in the global blacklist. 0 5.1.0
loadBalanceConnectionGroup Logical group of load-balanced
connections within a classloader, used to manage different groups
independently. If not specified, live management of load-balanced
connections is disabled. 5.1.13
loadBalanceExceptionChecker Fully-qualified class name of custom
exception checker. The class must implement
com.mysql.jdbc.LoadBalanceExceptionChecker interface, and is used
to inspect SQLExceptions and determine whether they should trigger
fail-over to another host in a load-balanced deployment.
com.mysql.jdbc.StandardLoadBalanceExceptionChecker 5.1.13
loadBalancePingTimeout Time in milliseconds to wait for ping
response from each of load-balanced physical connections when
using load-balanced Connection. 0 5.1.13
loadBalanceSQLExceptionSubclassFailover Comma-delimited list of
classes/interfaces used by default load-balanced exception checker
to determine whether a given SQLException should trigger failover.
The comparison is done using Class.isInstance(SQLException) using
the thrown SQLException. 5.1.13
loadBalanceSQLStateFailover Comma-delimited list of SQLState codes
used by default load-balanced exception checker to determine
whether a given SQLException should trigger failover. The SQLState
of a given SQLException is evaluated to determine whether it
begins with any value in the comma-delimited list. 5.1.13
loadBalanceValidateConnectionOnSwapServer Should the load-balanced
Connection explicitly check whether the connection is live when
swapping to a new physical connection at commit/rollback? false
5.1.13
maxRows The maximum number of rows to return (0, the default means
return all rows). -1 all versions
netTimeoutForStreamingResults What value should the driver
automatically set the server setting 'net_write_timeout' to when
the streaming result sets feature is in use? (value has unit of
seconds, the value '0' means the driver will not try and adjust
this value) 600 5.1.0
noAccessToProcedureBodies When determining procedure parameter
types for CallableStatements, and the connected user can't access
procedure bodies through "SHOW CREATE PROCEDURE" or select on
mysql.proc should the driver instead create basic metadata (all
parameters reported as IN VARCHARs, but allowing
registerOutParameter() to be called on them anyway) instead of
throwing an exception? false 5.0.3
noDatetimeStringSync Don't ensure that
ResultSet.getDatetimeType().toString().equals(ResultSet.getString(
)) false 3.1.7
noTimezoneConversionForTimeType Don't convert TIME values using
the server timezone if 'useTimezone'='true' false 5.0.0
nullCatalogMeansCurrent When DatabaseMetadataMethods ask for a
'catalog' parameter, does the value null mean use the current
catalog? (this is not JDBC-compliant, but follows legacy behavior
from earlier versions of the driver) true 3.1.8
nullNamePatternMatchesAll Should DatabaseMetaData methods that
accept *pattern parameters treat null the same as '%' (this is not
JDBC-compliant, however older versions of the driver accepted this
departure from the specification) true 3.1.8
overrideSupportsIntegrityEnhancementFacility Should the driver
return "true" for
DatabaseMetaData.supportsIntegrityEnhancementFacility() even if
the database doesn't support it to workaround applications that
require this method to return "true" to signal support of foreign
keys, even though the SQL specification states that this facility
contains much more than just foreign key support (one such
application being OpenOffice)? false 3.1.12
padCharsWithSpace If a result set column has the CHAR type and the
value does not fill the amount of characters specified in the DDL
for the column, should the driver pad the remaining characters
with space (for ANSI compliance)? false 5.0.6
pedantic Follow the JDBC spec to the letter. false 3.0.0
pinGlobalTxToPhysicalConnection When using XAConnections, should
the driver ensure that operations on a given XID are always routed
to the same physical connection? This allows the XAConnection to
support "XA START ... JOIN" after "XA END" has been called false
5.0.1
populateInsertRowWithDefaultValues When using ResultSets that are
CONCUR_UPDATABLE, should the driver pre-populate the "insert" row
with default values from the DDL for the table used in the query
so those values are immediately available for ResultSet accessors?
This functionality requires a call to the database for metadata
each time a result set of this type is created. If disabled (the
default), the default values will be populated by the an internal
call to refreshRow() which pulls back default values and/or values
changed by triggers. false 5.0.5
processEscapeCodesForPrepStmts Should the driver process escape
codes in queries that are prepared? true 3.1.12
queryTimeoutKillsConnection If the timeout given in
Statement.setQueryTimeout() expires, should the driver forcibly
abort the Connection instead of attempting to abort the query?
false 5.1.9
relaxAutoCommit If the version of MySQL the driver connects to
does not support transactions, still allow calls to commit(),
rollback() and setAutoCommit() (true/false, defaults to 'false')?
false 2.0.13
retainStatementAfterResultSetClose Should the driver retain the
Statement reference in a ResultSet after ResultSet.close() has
been called. This is not JDBC-compliant after JDBC-4.0. false
3.1.11
rollbackOnPooledClose Should the driver issue a rollback() when
the logical connection in a pool is closed? true 3.0.15
runningCTS13 Enables workarounds for bugs in Sun's JDBC compliance
testsuite version 1.3 false 3.1.7
serverTimezone Override detection/mapping of timezone. Used when
timezone from server doesn't map to Java timezone 3.0.2
statementInterceptors A comma-delimited list of classes that
implement "com.mysql.jdbc.StatementInterceptor" that should be
placed "in between" query execution to influence the results.
StatementInterceptors are "chainable", the results returned by the
"current" interceptor will be passed on to the next in in the
chain, from left-to-right order, as specified in this property.
5.1.1
strictFloatingPoint Used only in older versions of compliance test
false 3.0.0
strictUpdates Should the driver do strict checking (all primary
keys selected) of updatable result sets (true, false, defaults to
'true')? true 3.0.4
tinyInt1isBit Should the driver treat the datatype TINYINT(1) as
the BIT type (because the server silently converts BIT ->
TINYINT(1) when creating tables)? true 3.0.16
transformedBitIsBoolean If the driver converts TINYINT(1) to a
different type, should it use BOOLEAN instead of BIT for future
compatibility with MySQL-5.0, as MySQL-5.0 has a BIT type? false
3.1.9
treatUtilDateAsTimestamp Should the driver treat java.util.Date as
a TIMESTAMP for the purposes of PreparedStatement.setObject()?
true 5.0.5
ultraDevHack Create PreparedStatements for prepareCall() when
required, because UltraDev is broken and issues a prepareCall()
for _all_ statements? (true/false, defaults to 'false') false
2.0.3
useAffectedRows Don't set the CLIENT_FOUND_ROWS flag when
connecting to the server (not JDBC-compliant, will break most
applications that rely on "found" rows vs. "affected rows" for DML
statements), but does cause "correct" update counts from "INSERT
... ON DUPLICATE KEY UPDATE" statements to be returned by the
server. false 5.1.7
useGmtMillisForDatetimes Convert between session timezone and GMT
before creating Date and Timestamp instances (value of "false" is
legacy behavior, "true" leads to more JDBC-compliant behavior.
false 3.1.12
useHostsInPrivileges Add '@hostname' to users in
DatabaseMetaData.getColumn/TablePrivileges() (true/false),
defaults to 'true'. true 3.0.2
useInformationSchema When connected to MySQL-5.0.7 or newer,
should the driver use the INFORMATION_SCHEMA to derive information
used by DatabaseMetaData? false 5.0.0
useJDBCCompliantTimezoneShift Should the driver use JDBC-compliant
rules when converting TIME/TIMESTAMP/DATETIME values' timezone
information for those JDBC arguments which take a
java.util.Calendar argument? (Notice that this option is exclusive
of the "useTimezone=true" configuration option.) false 5.0.0
useLegacyDatetimeCode Use code for DATE/TIME/DATETIME/TIMESTAMP
handling in result sets and statements that consistently handles
timezone conversions from client to server and back again, or use
the legacy code for these datatypes that has been in the driver
for backwards-compatibility? true 5.1.6
useOldAliasMetadataBehavior Should the driver use the legacy
behavior for "AS" clauses on columns and tables, and only return
aliases (if any) for ResultSetMetaData.getColumnName() or
ResultSetMetaData.getTableName() rather than the original
column/table name? In 5.0.x, the default value was true. false
5.0.4
useOldUTF8Behavior Use the UTF-8 behavior the driver did when
communicating with 4.0 and older servers false 3.1.6
useOnlyServerErrorMessages Don't prepend 'standard' SQLState error
messages to error messages returned by the server. true 3.0.15
useSSPSCompatibleTimezoneShift If migrating from an environment
that was using server-side prepared statements, and the
configuration property "useJDBCCompliantTimeZoneShift" set to
"true", use compatible behavior when not using server-side
prepared statements when sending TIMESTAMP values to the MySQL
server. false 5.0.5
useServerPrepStmts Use server-side prepared statements if the
server supports them? false 3.1.0
useSqlStateCodes Use SQL Standard state codes instead of 'legacy'
X/Open/SQL state codes (true/false), default is 'true' true 3.1.3
useStreamLengthsInPrepStmts Honor stream length parameter in
PreparedStatement/ResultSet.setXXXStream() method calls
(true/false, defaults to 'true')? true 3.0.2
useTimezone Convert time/date types between client and server
timezones (true/false, defaults to 'false')? false 3.0.2
useUnbufferedInput Don't use BufferedInputStream for reading data
from the server true 3.0.11
yearIsDateType Should the JDBC driver treat the MySQL type "YEAR"
as a java.sql.Date, or as a SHORT? true 3.1.9
zeroDateTimeBehavior What should happen when the driver encounters
DATETIME values that are composed entirely of zeros (used by MySQL
to represent invalid dates)? Valid values are "exception", "round"
and "convertToNull". exception 3.1.4
Connector/J also supports access to MySQL using named pipes on
Windows NT, Windows 2000, or Windows XP using the
NamedPipeSocketFactory as a plugin-socket factory using the
socketFactory property. If you do not use a namedPipePath
property, the default of '\\.\pipe\MySQL' is used. If you use the
NamedPipeSocketFactory, the host name and port number values in
the JDBC url are ignored. To enable this feature, use:
socketFactory=com.mysql.jdbc.NamedPipeSocketFactory
Named pipes only work when connecting to a MySQL server on the
same physical machine where the JDBC driver is running. In simple
performance tests, named pipe access is between 30%-50% faster
than the standard TCP/IP access. However, this varies per system,
and named pipes are slower than TCP/IP in many Windows
configurations.
To create your own socket factories, follow the example code in
com.mysql.jdbc.NamedPipeSocketFactory, or
com.mysql.jdbc.StandardSocketFactory.
5.1.1. Properties Files for the useConfigs Option
The useConfigs connection option is a convenient shorthand for
specifying combinations of options for particular scenarios. The
argument values you can use with this option correspond to the
names of .properties files within the Connector/J
mysql-connector-java-version-bin.jar JAR file. For example, the
Connector/J 5.1.9 driver includes the following configuration
properties files:
$ unzip mysql-connector-java-5.1.19-bin.jar '*/configs/*'
Archive: mysql-connector-java-5.1.19-bin.jar
creating: com/mysql/jdbc/configs/
inflating: com/mysql/jdbc/configs/3-0-Compat.properties
inflating: com/mysql/jdbc/configs/5-0-Compat.properties
inflating: com/mysql/jdbc/configs/clusterBase.properties
inflating: com/mysql/jdbc/configs/coldFusion.properties
inflating: com/mysql/jdbc/configs/fullDebug.properties
inflating: com/mysql/jdbc/configs/maxPerformance.properties
inflating: com/mysql/jdbc/configs/solarisMaxPerformance.properties
To specify one of these combinations of options, specify
useConfigs=3-0-Compat, useConfigs=maxPerformance, and so on. The
following sections show the options that are part of each
useConfigs setting. For the details of why each one is included,
see the comments in the .properties files.
3-0-Compat
emptyStringsConvertToZero=true
jdbcCompliantTruncation=false
noDatetimeStringSync=true
nullCatalogMeansCurrent=true
nullNamePatternMatchesAll=true
transformedBitIsBoolean=false
dontTrackOpenResources=true
zeroDateTimeBehavior=convertToNull
useServerPrepStmts=false
autoClosePStmtStreams=true
processEscapeCodesForPrepStmts=false
useFastDateParsing=false
populateInsertRowWithDefaultValues=false
useDirectRowUnpack=false
5-0-Compat
useDirectRowUnpack=false
clusterBase
autoReconnect=true
failOverReadOnly=false
roundRobinLoadBalance=true
coldFusion
useDynamicCharsetInfo=false
alwaysSendSetIsolation=false
useLocalSessionState=true
autoReconnect=true
fullDebug
profileSQL=true
gatherPerMetrics=true
useUsageAdvisor=true
logSlowQueries=true
explainSlowQueries=true
maxPerformance
cachePrepStmts=true
cacheCallableStmts=true
cacheServerConfiguration=true
useLocalSessionState=true
elideSetAutoCommits=true
alwaysSendSetIsolation=false
enableQueryTimeouts=false
solarisMaxPerformance
useUnbufferedInput=false
useReadAheadInput=false
maintainTimeStats=false
5.2. JDBC API Implementation Notes
MySQL Connector/J passes all of the tests in the publicly
available version of Sun's JDBC compliance test suite. This
section gives details on a interface-by-interface level about
implementation decisions that might affect how you code
applications with MySQL Connector/J. The JDBC specification is
vague about how certain functionality should be implemented, or
the specification enables leeway in implementation.
* BLOB
Starting with Connector/J version 3.1.0, you can emulate BLOBs
with locators by adding the property emulateLocators=true to
your JDBC URL. Using this method, the driver will delay
loading the actual BLOB data until you retrieve the other data
and then use retrieval methods (getInputStream(), getBytes(),
and so forth) on the BLOB data stream.
You must use a column alias with the value of the column to
the actual name of the BLOB, for example:
SELECT id, 'data' as blob_data from blobtable
You must also follow these rules:
+ The SELECT
(http://dev.mysql.com/doc/refman/5.5/en/select.html) must
reference only one table. The table must have a primary
key
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glo
s_primary_key).
+ The SELECT
(http://dev.mysql.com/doc/refman/5.5/en/select.html) must
alias the original BLOB column name, specified as a
string, to an alternate name.
+ The SELECT
(http://dev.mysql.com/doc/refman/5.5/en/select.html) must
cover all columns that make up the primary key.
The BLOB implementation does not allow in-place modification
(they are copies, as reported by the
DatabaseMetaData.locatorsUpdateCopies() method). Because of
this, use the corresponding PreparedStatement.setBlob() or
ResultSet.updateBlob() (in the case of updatable result sets)
methods to save changes back to the database.
* CallableStatement
Starting with Connector/J 3.1.1, stored procedures are
supported when connecting to MySQL version 5.0 or newer using
the CallableStatement interface. Currently, the
getParameterMetaData() method of CallableStatement is not
supported.
* CLOB
The CLOB implementation does not allow in-place modification
(they are copies, as reported by the
DatabaseMetaData.locatorsUpdateCopies() method). Because of
this, use the PreparedStatement.setClob() method to save
changes back to the database. The JDBC API does not have a
ResultSet.updateClob() method.
* Connection
Unlike the pre-Connector/J JDBC driver (MM.MySQL), the
isClosed() method does not ping the server to determine if it
is available. In accordance with the JDBC specification, it
only returns true if closed() has been called on the
connection. If you need to determine if the connection is
still valid, issue a simple query, such as SELECT 1. The
driver will throw an exception if the connection is no longer
valid.
* DatabaseMetaData
Foreign key
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_for
eign_key) information (getImportedKeys()/getExportedKeys() and
getCrossReference()) is only available from InnoDB
(http://dev.mysql.com/doc/refman/5.5/en/innodb-storage-engine.
html) tables. The driver uses SHOW CREATE TABLE
(http://dev.mysql.com/doc/refman/5.5/en/show-create-table.html
) to retrieve this information, so if any other storage
engines add support for foreign keys, the driver would
transparently support them as well.
* PreparedStatement
PreparedStatements are implemented by the driver, as MySQL
does not have a prepared statement feature. Because of this,
the driver does not implement getParameterMetaData() or
getMetaData() as it would require the driver to have a
complete SQL parser in the client.
Starting with version 3.1.0 MySQL Connector/J, server-side
prepared statements and binary-encoded result sets are used
when the server supports them.
Take care when using a server-side prepared statement with
large parameters that are set using setBinaryStream(),
setAsciiStream(), setUnicodeStream(), setBlob(), or setClob().
To re-execute the statement with any large parameter changed
to a nonlarge parameter, call clearParameters() and set all
parameters again. The reason for this is as follows:
+ During both server-side prepared statements and
client-side emulation, large data is exchanged only when
PreparedStatement.execute() is called.
+ Once that has been done, the stream used to read the data
on the client side is closed (as per the JDBC spec), and
cannot be read from again.
+ If a parameter changes from large to nonlarge, the driver
must reset the server-side state of the prepared
statement to allow the parameter that is being changed to
take the place of the prior large value. This removes all
of the large data that has already been sent to the
server, thus requiring the data to be re-sent, using the
setBinaryStream(), setAsciiStream(), setUnicodeStream(),
setBlob() or setClob() method.
Consequently, to change the type of a parameter to a nonlarge
one, you must call clearParameters() and set all parameters of
the prepared statement again before it can be re-executed.
* ResultSet
By default, ResultSets are completely retrieved and stored in
memory. In most cases this is the most efficient way to
operate, and due to the design of the MySQL network protocol
is easier to implement. If you are working with ResultSets
that have a large number of rows or large values, and cannot
allocate heap space in your JVM for the memory required, you
can tell the driver to stream the results back one row at a
time.
To enable this functionality, create a Statement instance in
the following manner:
stmt = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
java.sql.ResultSet.CONCUR_READ_ONLY);
stmt.setFetchSize(Integer.MIN_VALUE);
The combination of a forward-only, read-only result set, with
a fetch size of Integer.MIN_VALUE serves as a signal to the
driver to stream result sets row-by-row. After this, any
result sets created with the statement will be retrieved
row-by-row.
There are some caveats with this approach. You must read all
of the rows in the result set (or close it) before you can
issue any other queries on the connection, or an exception
will be thrown.
The earliest the locks these statements hold can be released
(whether they be MyISAM table-level locks or row-level locks
in some other storage engine such as InnoDB) is when the
statement completes.
If the statement is within scope of a transaction, then locks
are released when the transaction completes (which implies
that the statement needs to complete first). As with most
other databases, statements are not complete until all the
results pending on the statement are read or the active result
set for the statement is closed.
Therefore, if using streaming results, process them as quickly
as possible if you want to maintain concurrent access to the
tables referenced by the statement producing the result set.
* ResultSetMetaData
The isAutoIncrement() method only works when using MySQL
servers 4.0 and newer.
* Statement
When using versions of the JDBC driver earlier than 3.2.1, and
connected to server versions earlier than 5.0.3, the
setFetchSize() method has no effect, other than to toggle
result set streaming as described above.
Connector/J 5.0.0 and later include support for both
Statement.cancel() and Statement.setQueryTimeout(). Both
require MySQL 5.0.0 or newer server, and require a separate
connection to issue the KILL QUERY
(http://dev.mysql.com/doc/refman/5.5/en/kill.html) statement.
In the case of setQueryTimeout(), the implementation creates
an additional thread to handle the timeout functionality.
Note
Failures to cancel the statement for setQueryTimeout() may
manifest themselves as RuntimeException rather than failing
silently, as there is currently no way to unblock the thread
that is executing the query being cancelled due to timeout
expiration and have it throw the exception instead.
Note
The MySQL statement KILL QUERY
(http://dev.mysql.com/doc/refman/5.5/en/kill.html) (which is
what the driver uses to implement Statement.cancel()) is
non-deterministic; thus, avoid the use of Statement.cancel()
if possible. If no query is in process, the next query issued
will be killed by the server. This race condition is guarded
against as of Connector/J 5.1.18.
MySQL does not support SQL cursors, and the JDBC driver
doesn't emulate them, so setCursorName() has no effect.
Connector/J 5.1.3 and later include two additional methods:
+ setLocalInfileInputStream() sets an InputStream instance
that will be used to send data to the MySQL server for a
LOAD DATA LOCAL INFILE
(http://dev.mysql.com/doc/refman/5.5/en/load-data.html)
statement rather than a FileInputStream or URLInputStream
that represents the path given as an argument to the
statement.
This stream will be read to completion upon execution of
a LOAD DATA LOCAL INFILE
(http://dev.mysql.com/doc/refman/5.5/en/load-data.html)
statement, and will automatically be closed by the
driver, so it needs to be reset before each call to
execute*() that would cause the MySQL server to request
data to fulfill the request for LOAD DATA LOCAL INFILE
(http://dev.mysql.com/doc/refman/5.5/en/load-data.html).
If this value is set to NULL, the driver will revert to
using a FileInputStream or URLInputStream as required.
+ getLocalInfileInputStream() returns the InputStream
instance that will be used to send data in response to a
LOAD DATA LOCAL INFILE
(http://dev.mysql.com/doc/refman/5.5/en/load-data.html)
statement.
This method returns NULL if no such stream has been set
using setLocalInfileInputStream().
5.3. Java, JDBC and MySQL Types
MySQL Connector/J is flexible in the way it handles conversions
between MySQL data types and Java data types.
In general, any MySQL data type can be converted to a
java.lang.String, and any numeric type can be converted to any of
the Java numeric types, although round-off, overflow, or loss of
precision may occur.
Note
All TEXT types return Types.LONGVARCHAR with different
getPrecision() values (65535, 255, 16777215, and 2147483647
respectively) with getColumnType() returning -1. This behavior is
intentional even though TINYTEXT does not fall, regarding to its
size, within the LONGVARCHAR category. This is to avoid different
handling inside the same base type. And getColumnType() returns -1
because the internal server handling is of type TEXT, which is
similar to BLOB.
Also note that getColumnTypeName() will return VARCHAR even though
getColumnType() returns Types.LONGVARCHAR, because VARCHAR is the
designated column database-specific name for this type.
Starting with Connector/J 3.1.0, the JDBC driver issues warnings
or throws DataTruncation exceptions as is required by the JDBC
specification unless the connection was configured not to do so by
using the property jdbcCompliantTruncation and setting it to
false.
The conversions that are always guaranteed to work are listed in
the following table. The first column lists one or more MySQL data
types, and the second column lists one or more Java types to which
the MySQL types can be converted.
Table 5.1. Connection Properties - Miscellaneous
These MySQL Data Types Can always be converted to these Java types
CHAR, VARCHAR, BLOB, TEXT, ENUM, and SET java.lang.String,
java.io.InputStream, java.io.Reader, java.sql.Blob, java.sql.Clob
FLOAT, REAL, DOUBLE PRECISION, NUMERIC, DECIMAL, TINYINT,
SMALLINT, MEDIUMINT, INTEGER, BIGINT java.lang.String,
java.lang.Short, java.lang.Integer, java.lang.Long,
java.lang.Double, java.math.BigDecimal
DATE, TIME, DATETIME, TIMESTAMP java.lang.String, java.sql.Date,
java.sql.Timestamp
Note
Round-off, overflow or loss of precision may occur if you choose a
Java numeric data type that has less precision or capacity than
the MySQL data type you are converting to/from.
The ResultSet.getObject() method uses the type conversions between
MySQL and Java types, following the JDBC specification where
appropriate. The value returned by
ResultSetMetaData.GetColumnClassName() is also shown below. For
more information on the java.sql.Types classes see Java 2 Platform
Types
(http://java.sun.com/j2se/1.4.2/docs/api/java/sql/Types.html).
Table 5.2. MySQL Types to Java Types for ResultSet.getObject()
MySQL Type Name Return value of GetColumnClassName Returned as
Java Class
BIT(1) (new in MySQL-5.0) BIT java.lang.Boolean
BIT( > 1) (new in MySQL-5.0) BIT byte[]
TINYINT TINYINT java.lang.Boolean if the configuration property
tinyInt1isBit is set to true (the default) and the storage size is
1, or java.lang.Integer if not.
BOOL, BOOLEAN TINYINT See TINYINT, above as these are aliases for
TINYINT(1), currently.
SMALLINT[(M)] [UNSIGNED] SMALLINT [UNSIGNED] java.lang.Integer
(regardless if UNSIGNED or not)
MEDIUMINT[(M)] [UNSIGNED] MEDIUMINT [UNSIGNED] java.lang.Integer,
if UNSIGNED java.lang.Long (C/J 3.1 and earlier), or
java.lang.Integer for C/J 5.0 and later
INT,INTEGER[(M)] [UNSIGNED] INTEGER [UNSIGNED] java.lang.Integer,
if UNSIGNED java.lang.Long
BIGINT[(M)] [UNSIGNED] BIGINT [UNSIGNED] java.lang.Long, if
UNSIGNED java.math.BigInteger
FLOAT[(M,D)] FLOAT java.lang.Float
DOUBLE[(M,B)] DOUBLE java.lang.Double
DECIMAL[(M[,D])] DECIMAL java.math.BigDecimal
DATE DATE java.sql.Date
DATETIME DATETIME java.sql.Timestamp
TIMESTAMP[(M)] TIMESTAMP java.sql.Timestamp
TIME TIME java.sql.Time
YEAR[(2|4)] YEAR If yearIsDateType configuration property is set
to false, then the returned object type is java.sql.Short. If set
to true (the default), then the returned object is of type
java.sql.Date with the date set to January 1st, at midnight.
CHAR(M) CHAR java.lang.String (unless the character set for the
column is BINARY, then byte[] is returned.
VARCHAR(M) [BINARY] VARCHAR java.lang.String (unless the character
set for the column is BINARY, then byte[] is returned.
BINARY(M) BINARY byte[]
VARBINARY(M) VARBINARY byte[]
TINYBLOB TINYBLOB byte[]
TINYTEXT VARCHAR java.lang.String
BLOB BLOB byte[]
TEXT VARCHAR java.lang.String
MEDIUMBLOB MEDIUMBLOB byte[]
MEDIUMTEXT VARCHAR java.lang.String
LONGBLOB LONGBLOB byte[]
LONGTEXT VARCHAR java.lang.String
ENUM('value1','value2',...) CHAR java.lang.String
SET('value1','value2',...) CHAR java.lang.String
5.4. Using Character Sets and Unicode
All strings sent from the JDBC driver to the server are converted
automatically from native Java Unicode form to the client
character encoding, including all queries sent using
Statement.execute(), Statement.executeUpdate(),
Statement.executeQuery() as well as all PreparedStatement and
CallableStatement parameters with the exclusion of parameters set
using setBytes(), setBinaryStream(), setAsciiStream(),
setUnicodeStream() and setBlob().
Number of Encodings Per Connection
In MySQL Server 4.1 and higher, Connector/J supports a single
character encoding between client and server, and any number of
character encodings for data returned by the server to the client
in ResultSets.
Prior to MySQL Server 4.1, Connector/J supported a single
character encoding per connection, which could either be
automatically detected from the server configuration, or could be
configured by the user through the useUnicode and
characterEncoding properties.
Setting the Character Encoding
The character encoding between client and server is automatically
detected upon connection. You specify the encoding on the server
using the character_set_server
(http://dev.mysql.com/doc/refman/5.5/en/server-system-variables.ht
ml#sysvar_character_set_server) for server versions 4.1.0 and
newer, and character_set system variable for server versions older
than 4.1.0. The driver automatically uses the encoding specified
by the server. For more information, see Server Character Set and
Collation
(http://dev.mysql.com/doc/refman/5.5/en/charset-server.html).
For example, to use 4-byte UTF-8 character sets with Connector/J,
configure the MySQL server with character_set_server=utf8mb4
(http://dev.mysql.com/doc/refman/5.5/en/server-system-variables.ht
ml#sysvar_character_set_server), and leave characterEncoding out
of the Connector/J connection string. Connector/J will then
autodetect the UTF-8 setting.
To override the automatically detected encoding on the client
side, use the characterEncoding property in the URL used to
connect to the server.
To allow multiple character sets to be sent from the client, use
the UTF-8 encoding, either by configuring utf8 as the default
server character set, or by configuring the JDBC driver to use
UTF-8 through the characterEncoding property.
When specifying character encodings on the client side, use
Java-style names. The following table lists MySQL character set
names and the corresponding Java-style names:
Table 5.3. MySQL to Java Encoding Name Translations
MySQL Character Set Name Java-Style Character Encoding Name
ascii US-ASCII
big5 Big5
gbk GBK
sjis SJIS (or Cp932 or MS932 for MySQL Server < 4.1.11)
cp932 Cp932 or MS932 (MySQL Server > 4.1.11)
gb2312 EUC_CN
ujis EUC_JP
euckr EUC_KR
latin1 Cp1252
latin2 ISO8859_2
greek ISO8859_7
hebrew ISO8859_8
cp866 Cp866
tis620 TIS620
cp1250 Cp1250
cp1251 Cp1251
cp1257 Cp1257
macroman MacRoman
macce MacCentralEurope
utf8 UTF-8
ucs2 UnicodeBig
Warning
Do not issue the query set names with Connector/J, as the driver
will not detect that the character set has changed, and will
continue to use the character set detected during the initial
connection setup.
5.5. Connecting Securely Using SSL
SSL in MySQL Connector/J encrypts all data (other than the initial
handshake) between the JDBC driver and the server. The performance
penalty for enabling SSL is an increase in query processing time
between 35% and 50%, depending on the size of the query, and the
amount of data it returns.
For SSL support to work, you must have the following:
* A JDK that includes JSSE (Java Secure Sockets Extension), like
JDK-1.4.1 or newer. SSL does not currently work with a JDK
that you can add JSSE to, like JDK-1.2.x or JDK-1.3.x due to
the following JSSE bug:
http://developer.java.sun.com/developer/bugParade/bugs/4273544
.html
* A MySQL server that supports SSL and has been compiled and
configured to do so, which is MySQL 4.0.4 or later. For more
information, see Configuring MySQL for SSL
(http://dev.mysql.com/doc/refman/5.5/en/configuring-for-ssl.ht
ml).
* A client certificate (covered later in this section)
The system works through two Java truststore files, one file
contains the certificate information for the server (truststore in
the examples below). The other file contains the certificate for
the client (keystore in the examples below). All Java truststore
files are password protected by supplying a suitable password to
the keytool when you create the files. You need the file names and
associated passwords to create an SSL connection.
You will first need to import the MySQL server CA Certificate into
a Java truststore. A sample MySQL server CA Certificate is located
in the SSL subdirectory of the MySQL source distribution. This is
what SSL will use to determine if you are communicating with a
secure MySQL server. Alternatively, use the CA Certificate that
you have generated or been provided with by your SSL provider.
To use Java's keytool to create a truststore in the current
directory , and import the server's CA certificate (cacert.pem),
you can do the following (assuming that keytool is in your path.
The keytool is typically located in the bin subdirectory of your
JDK or JRE):
shell> keytool -import -alias mysqlServerCACert \
-file cacert.pem -key
store truststore
Enter the password when prompted for the keystore file.
Interaction with keytool looks like this:
Enter keystore password: *********
Owner: EMAILADDRESS=walrus@example.com, CN=Walrus,
O=MySQL AB, L=Orenburg, ST=Some-State, C=RU
Issuer: EMAILADDRESS=walrus@example.com, CN=Walrus,
O=MySQL AB, L=Orenburg, ST=Some-State, C=RU
Serial number: 0
Valid from:
Fri Aug 02 16:55:53 CDT 2002 until: Sat Aug 02 16:55:53 CDT 2003
Certificate fingerprints:
MD5: 61:91:A0:F2:03:07:61:7A:81:38:66:DA:19:C4:8D:AB
SHA1: 25:77:41:05:D5:AD:99:8C:14:8C:CA:68:9C:2F:B8:89:C3:34:4D:6C
Trust this certificate? [no]: yes
Certificate was added to keystore
You then have two options: either import the client certificate
that matches the CA certificate you just imported, or create a new
client certificate.
Importing an existing certificate requires the certificate to be
in DER format. You can use openssl to convert an existing
certificate into the new format. For example:
shell> openssl x509 -outform DER -in client-cert.pem -out client.cert
Now import the converted certificate into your keystore using
keytool:
shell> keytool -import -file client.cert -keystore keystore -alias my
sqlClientCertificate
To generate your own client certificate, use keytool to create a
suitable certificate and add it to the keystore file:
shell> keytool -genkey -keyalg rsa \
-alias mysqlClientCertificate -keystore keystore
Keytool will prompt you for the following information, and create
a keystore named keystore in the current directory.
Respond with information that is appropriate for your situation:
Enter keystore password: *********
What is your first and last name?
[Unknown]: Matthews
What is the name of your organizational unit?
[Unknown]: Software Development
What is the name of your organization?
[Unknown]: MySQL AB
What is the name of your City or Locality?
[Unknown]: Flossmoor
What is the name of your State or Province?
[Unknown]: IL
What is the two-letter country code for this unit?
[Unknown]: US
Is <CN=Matthews, OU=Software Development, O=MySQL AB,
L=Flossmoor, ST=IL, C=US> correct?
[no]: y
Enter key password for <mysqlClientCertificate>
(RETURN if same as keystore password):
Finally, to get JSSE to use the keystore and truststore that you
have generated, you need to set the following system properties
when you start your JVM, replacing path_to_keystore_file with the
full path to the keystore file you created,
path_to_truststore_file with the path to the truststore file you
created, and using the appropriate password values for each
property. You can do this either on the command line:
-Djavax.net.ssl.keyStore=path_to_keystore_file
-Djavax.net.ssl.keyStorePassword=password
-Djavax.net.ssl.trustStore=path_to_truststore_file
-Djavax.net.ssl.trustStorePassword=password
Or you can set the values directly within the application:
System.setProperty("javax.net.ssl.keyStore","path_to_keystore_file");
System.setProperty("javax.net.ssl.keyStorePassword","password");
System.setProperty("javax.net.ssl.trustStore","path_to_truststore_fil
e");
System.setProperty("javax.net.ssl.trustStorePassword","password");
You will also need to set useSSL to true in your connection
parameters for MySQL Connector/J, either by adding useSSL=true to
your URL, or by setting the property useSSL to true in the
java.util.Properties instance you pass to
DriverManager.getConnection().
You can test that SSL is working by turning on JSSE debugging (as
detailed below), and look for the following key events:
...
*** ClientHello, v3.1
RandomCookie: GMT: 1018531834 bytes = { 199, 148, 180, 215, 74, 12,
??
54, 244, 0, 168, 55, 103, 215, 64, 16, 138, 225, 190, 132, 153, 2,
??
217, 219, 239, 202, 19, 121, 78 }
Session ID: {}
Cipher Suites: { 0, 5, 0, 4, 0, 9, 0, 10, 0, 18, 0, 19, 0, 3, 0, 17
}
Compression Methods: { 0 }
***
[write] MD5 and SHA1 hashes: len = 59
0000: 01 00 00 37 03 01 3D B6 90 FA C7 94 B4 D7 4A 0C ...7..=.......
J.
0010: 36 F4 00 A8 37 67 D7 40 10 8A E1 BE 84 99 02 D9 6...7g.@......
..
0020: DB EF CA 13 79 4E 00 00 10 00 05 00 04 00 09 00 ....yN........
..
0030: 0A 00 12 00 13 00 03 00 11 01 00 ...........
main, WRITE: SSL v3.1 Handshake, length = 59
main, READ: SSL v3.1 Handshake, length = 74
*** ServerHello, v3.1
RandomCookie: GMT: 1018577560 bytes = { 116, 50, 4, 103, 25, 100, 58
, ??
202, 79, 185, 178, 100, 215, 66, 254, 21, 83, 187, 190, 42, 170, 3
, ??
132, 110, 82, 148, 160, 92 }
Session ID: {163, 227, 84, 53, 81, 127, 252, 254, 178, 179, 68, 63,
??
182, 158, 30, 11, 150, 79, 170, 76, 255, 92, 15, 226, 24, 17, 177,
??
219, 158, 177, 187, 143}
Cipher Suite: { 0, 5 }
Compression Method: 0
***
%% Created: [Session-1, SSL_RSA_WITH_RC4_128_SHA]
** SSL_RSA_WITH_RC4_128_SHA
[read] MD5 and SHA1 hashes: len = 74
0000: 02 00 00 46 03 01 3D B6 43 98 74 32 04 67 19 64 ...F..=.C.t2.g
.d
0010: 3A CA 4F B9 B2 64 D7 42 FE 15 53 BB BE 2A AA 03 :.O..d.B..S..*
..
0020: 84 6E 52 94 A0 5C 20 A3 E3 54 35 51 7F FC FE B2 .nR..\ ..T5Q..
..
0030: B3 44 3F B6 9E 1E 0B 96 4F AA 4C FF 5C 0F E2 18 .D?.....O.L.\.
..
0040: 11 B1 DB 9E B1 BB 8F 00 05 00 ..........
main, READ: SSL v3.1 Handshake, length = 1712
...
JSSE provides debugging (to stdout) when you set the following
system property: -Djavax.net.debug=all This will tell you what
keystores and truststores are being used, as well as what is going
on during the SSL handshake and certificate exchange. It will be
helpful when trying to determine what is not working when trying
to get an SSL connection to happen.
5.6. Connecting Using PAM Authentication
Java applications using Connector/J 5.1.21 and higher can can
connect to MySQL servers that use the pluggable authentication
module (PAM) authentication scheme.
For PAM authentication to work, you must have the following:
* A MySQL server that supports PAM authentication: a commercial
distribution of MySQL 5.5.16 or higher. See The PAM
Authentication Plugin
(http://dev.mysql.com/doc/refman/5.5/en/pam-authentication-plu
gin.html) for more information. Connector/J implements the
same cleartext authentication method as in The Cleartext
Client-Side Authentication Plugin
(http://dev.mysql.com/doc/refman/5.5/en/cleartext-authenticati
on-plugin.html).
* SSL capability, as explained in Section 5.5, "Connecting
Securely Using SSL." Because the PAM authentication scheme
sends the original password to the server, the connection to
the server must be encrypted.
PAM authentication support is enabled by default in Connector/J
5.1.21 and up, so no extra configuration is needed.
To disable the PAM authentication feature, specify
mysql_clear_password (the method) or
com.mysql.jdbc.authentication.MysqlClearPasswordPlugin (the class
name) in the comma-separated list of arguments for the
disabledAuthenticationPlugins connection option. See Section 5.1,
"Driver/Datasource Class Names, URL Syntax and Configuration
Properties for Connector/J" for details about that connection
option.
5.7. Using Master/Slave Replication with ReplicationConnection
Connector/J 3.1.7 and higher includes a variant of the driver that
will automatically send queries to a read/write master, or a
failover or round-robin loadbalanced set of slaves based on the
state of Connection.getReadOnly().
An application signals that it wants a transaction to be read-only
by calling Connection.setReadOnly(true), this replication-aware
connection will use one of the slave connections, which are
load-balanced per-vm using a round-robin scheme (a given
connection is sticky to a slave unless that slave is removed from
service). If you have a write transaction, or if you have a read
that is time-sensitive (remember, replication in MySQL is
asynchronous), set the connection to be not read-only, by calling
Connection.setReadOnly(false) and the driver will ensure that
further calls are sent to the master MySQL server. The driver
takes care of propagating the current state of autocommit,
isolation level, and catalog between all of the connections that
it uses to accomplish this load balancing functionality.
To enable this functionality, use the
com.mysql.jdbc.ReplicationDriver class when configuring your
application server's connection pool or when creating an instance
of a JDBC driver for your standalone application. Because it
accepts the same URL format as the standard MySQL JDBC driver,
ReplicationDriver does not currently work with
java.sql.DriverManager-based connection creation unless it is the
only MySQL JDBC driver registered with the DriverManager .
Here is a short example of how ReplicationDriver might be used in
a standalone application:
import java.sql.Connection;
import java.sql.ResultSet;
import java.util.Properties;
import com.mysql.jdbc.ReplicationDriver;
public class ReplicationDriverDemo {
public static void main(String[] args) throws Exception {
ReplicationDriver driver = new ReplicationDriver();
Properties props = new Properties();
// We want this for failover on the slaves
props.put("autoReconnect", "true");
// We want to load balance between the slaves
props.put("roundRobinLoadBalance", "true");
props.put("user", "foo");
props.put("password", "bar");
//
// Looks like a normal MySQL JDBC url, with a
// comma-separated list of hosts, the first
// being the 'master', the rest being any number
// of slaves that the driver will load balance against
//
Connection conn =
driver.connect("jdbc:mysql:replication://master,slave1,slave2
,slave3/test",
props);
//
// Perform read/write work on the master
// by setting the read-only flag to "false"
//
conn.setReadOnly(false);
conn.setAutoCommit(false);
conn.createStatement().executeUpdate("UPDATE some_table ....");
conn.commit();
//
// Now, do a query from a slave, the driver automatically picks o
ne
// from the list
//
conn.setReadOnly(true);
ResultSet rs =
conn.createStatement().executeQuery("SELECT a,b FROM alt_table"
);
.......
}
}
Consider investigating the Load Balancing JDBC Pool (lbpool) tool,
which provides a wrapper around the standard JDBC driver and
enables you to use DB connection pools that includes checks for
system failures and uneven load distribution. For more
information, see Load Balancing JDBC Pool (lbpool)
(http://code.tailrank.com/lbpool).
5.8. Mapping MySQL Error Numbers to JDBC SQLState Codes
The table below provides a mapping of the MySQL error numbers to
JDBC SQLState values.
Table 5.4. Mapping of MySQL Error Numbers to SQLStates
MySQL Error Number MySQL Error Name Legacy (X/Open) SQLState SQL
Standard SQLState
1022 ER_DUP_KEY S1000 23000
1037 ER_OUTOFMEMORY S1001 HY001
1038 ER_OUT_OF_SORTMEMORY S1001 HY001
1040 ER_CON_COUNT_ERROR 08004 08004
1042 ER_BAD_HOST_ERROR 08004 08S01
1043 ER_HANDSHAKE_ERROR 08004 08S01
1044 ER_DBACCESS_DENIED_ERROR S1000 42000
1045 ER_ACCESS_DENIED_ERROR 28000 28000
1047 ER_UNKNOWN_COM_ERROR 08S01 HY000
1050 ER_TABLE_EXISTS_ERROR S1000 42S01
1051 ER_BAD_TABLE_ERROR 42S02 42S02
1052 ER_NON_UNIQ_ERROR S1000 23000
1053 ER_SERVER_SHUTDOWN S1000 08S01
1054 ER_BAD_FIELD_ERROR S0022 42S22
1055 ER_WRONG_FIELD_WITH_GROUP S1009 42000
1056 ER_WRONG_GROUP_FIELD S1009 42000
1057 ER_WRONG_SUM_SELECT S1009 42000
1058 ER_WRONG_VALUE_COUNT 21S01 21S01
1059 ER_TOO_LONG_IDENT S1009 42000
1060 ER_DUP_FIELDNAME S1009 42S21
1061 ER_DUP_KEYNAME S1009 42000
1062 ER_DUP_ENTRY S1009 23000
1063 ER_WRONG_FIELD_SPEC S1009 42000
1064 ER_PARSE_ERROR 42000 42000
1065 ER_EMPTY_QUERY 42000 42000
1066 ER_NONUNIQ_TABLE S1009 42000
1067 ER_INVALID_DEFAULT S1009 42000
1068 ER_MULTIPLE_PRI_KEY S1009 42000
1069 ER_TOO_MANY_KEYS S1009 42000
1070 ER_TOO_MANY_KEY_PARTS S1009 42000
1071 ER_TOO_LONG_KEY S1009 42000
1072 ER_KEY_COLUMN_DOES_NOT_EXITS S1009 42000
1073 ER_BLOB_USED_AS_KEY S1009 42000
1074 ER_TOO_BIG_FIELDLENGTH S1009 42000
1075 ER_WRONG_AUTO_KEY S1009 42000
1080 ER_FORCING_CLOSE S1000 08S01
1081 ER_IPSOCK_ERROR 08S01 08S01
1082 ER_NO_SUCH_INDEX S1009 42S12
1083 ER_WRONG_FIELD_TERMINATORS S1009 42000
1084 ER_BLOBS_AND_NO_TERMINATED S1009 42000
1090 ER_CANT_REMOVE_ALL_FIELDS S1000 42000
1091 ER_CANT_DROP_FIELD_OR_KEY S1000 42000
1101 ER_BLOB_CANT_HAVE_DEFAULT S1000 42000
1102 ER_WRONG_DB_NAME S1000 42000
1103 ER_WRONG_TABLE_NAME S1000 42000
1104 ER_TOO_BIG_SELECT S1000 42000
1106 ER_UNKNOWN_PROCEDURE S1000 42000
1107 ER_WRONG_PARAMCOUNT_TO_PROCEDURE S1000 42000
1109 ER_UNKNOWN_TABLE S1000 42S02
1110 ER_FIELD_SPECIFIED_TWICE S1000 42000
1112 ER_UNSUPPORTED_EXTENSION S1000 42000
1113 ER_TABLE_MUST_HAVE_COLUMNS S1000 42000
1115 ER_UNKNOWN_CHARACTER_SET S1000 42000
1118 ER_TOO_BIG_ROWSIZE S1000 42000
1120 ER_WRONG_OUTER_JOIN S1000 42000
1121 ER_NULL_COLUMN_IN_INDEX S1000 42000
1129 ER_HOST_IS_BLOCKED 08004 HY000
1130 ER_HOST_NOT_PRIVILEGED 08004 HY000
1131 ER_PASSWORD_ANONYMOUS_USER S1000 42000
1132 ER_PASSWORD_NOT_ALLOWED S1000 42000
1133 ER_PASSWORD_NO_MATCH S1000 42000
1136 ER_WRONG_VALUE_COUNT_ON_ROW S1000 21S01
1138 ER_INVALID_USE_OF_NULL S1000 42000
1139 ER_REGEXP_ERROR S1000 42000
1140 ER_MIX_OF_GROUP_FUNC_AND_FIELDS S1000 42000
1141 ER_NONEXISTING_GRANT S1000 42000
1142 ER_TABLEACCESS_DENIED_ERROR S1000 42000
1143 ER_COLUMNACCESS_DENIED_ERROR S1000 42000
1144 ER_ILLEGAL_GRANT_FOR_TABLE S1000 42000
1145 ER_GRANT_WRONG_HOST_OR_USER S1000 42000
1146 ER_NO_SUCH_TABLE S1000 42S02
1147 ER_NONEXISTING_TABLE_GRANT S1000 42000
1148 ER_NOT_ALLOWED_COMMAND S1000 42000
1149 ER_SYNTAX_ERROR S1000 42000
1152 ER_ABORTING_CONNECTION S1000 08S01
1153 ER_NET_PACKET_TOO_LARGE S1000 08S01
1154 ER_NET_READ_ERROR_FROM_PIPE S1000 08S01
1155 ER_NET_FCNTL_ERROR S1000 08S01
1156 ER_NET_PACKETS_OUT_OF_ORDER S1000 08S01
1157 ER_NET_UNCOMPRESS_ERROR S1000 08S01
1158 ER_NET_READ_ERROR S1000 08S01
1159 ER_NET_READ_INTERRUPTED S1000 08S01
1160 ER_NET_ERROR_ON_WRITE S1000 08S01
1161 ER_NET_WRITE_INTERRUPTED S1000 08S01
1162 ER_TOO_LONG_STRING S1000 42000
1163 ER_TABLE_CANT_HANDLE_BLOB S1000 42000
1164 ER_TABLE_CANT_HANDLE_AUTO_INCREMENT S1000 42000
1166 ER_WRONG_COLUMN_NAME S1000 42000
1167 ER_WRONG_KEY_COLUMN S1000 42000
1169 ER_DUP_UNIQUE S1000 23000
1170 ER_BLOB_KEY_WITHOUT_LENGTH S1000 42000
1171 ER_PRIMARY_CANT_HAVE_NULL S1000 42000
1172 ER_TOO_MANY_ROWS S1000 42000
1173 ER_REQUIRES_PRIMARY_KEY S1000 42000
1177 ER_CHECK_NO_SUCH_TABLE S1000 42000
1178 ER_CHECK_NOT_IMPLEMENTED S1000 42000
1179 ER_CANT_DO_THIS_DURING_AN_TRANSACTION S1000 25000
1184 ER_NEW_ABORTING_CONNECTION S1000 08S01
1189 ER_MASTER_NET_READ S1000 08S01
1190 ER_MASTER_NET_WRITE S1000 08S01
1203 ER_TOO_MANY_USER_CONNECTIONS S1000 42000
1205 ER_LOCK_WAIT_TIMEOUT 41000 41000
1207 ER_READ_ONLY_TRANSACTION S1000 25000
1211 ER_NO_PERMISSION_TO_CREATE_USER S1000 42000
1213 ER_LOCK_DEADLOCK 41000 40001
1216 ER_NO_REFERENCED_ROW S1000 23000
1217 ER_ROW_IS_REFERENCED S1000 23000
1218 ER_CONNECT_TO_MASTER S1000 08S01
1222 ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT S1000 21000
1226 ER_USER_LIMIT_REACHED S1000 42000
1230 ER_NO_DEFAULT S1000 42000
1231 ER_WRONG_VALUE_FOR_VAR S1000 42000
1232 ER_WRONG_TYPE_FOR_VAR S1000 42000
1234 ER_CANT_USE_OPTION_HERE S1000 42000
1235 ER_NOT_SUPPORTED_YET S1000 42000
1239 ER_WRONG_FK_DEF S1000 42000
1241 ER_OPERAND_COLUMNS S1000 21000
1242 ER_SUBQUERY_NO_1_ROW S1000 21000
1247 ER_ILLEGAL_REFERENCE S1000 42S22
1248 ER_DERIVED_MUST_HAVE_ALIAS S1000 42000
1249 ER_SELECT_REDUCED S1000 01000
1250 ER_TABLENAME_NOT_ALLOWED_HERE S1000 42000
1251 ER_NOT_SUPPORTED_AUTH_MODE S1000 08004
1252 ER_SPATIAL_CANT_HAVE_NULL S1000 42000
1253 ER_COLLATION_CHARSET_MISMATCH S1000 42000
1261 ER_WARN_TOO_FEW_RECORDS S1000 01000
1262 ER_WARN_TOO_MANY_RECORDS S1000 01000
1263 ER_WARN_NULL_TO_NOTNULL S1000 01000
1264 ER_WARN_DATA_OUT_OF_RANGE S1000 01000
1265 ER_WARN_DATA_TRUNCATED S1000 01000
1280 ER_WRONG_NAME_FOR_INDEX S1000 42000
1281 ER_WRONG_NAME_FOR_CATALOG S1000 42000
1286 ER_UNKNOWN_STORAGE_ENGINE S1000 42000
Chapter 6. JDBC Concepts
This section provides some general JDBC background.
6.1. Connecting to MySQL Using the JDBC DriverManager Interface
When you are using JDBC outside of an application server, the
DriverManager class manages the establishment of Connections.
Specify to the DriverManager which JDBC drivers to try to make
Connections with. The easiest way to do this is to use
Class.forName() on the class that implements the java.sql.Driver
interface. With MySQL Connector/J, the name of this class is
com.mysql.jdbc.Driver. With this method, you could use an external
configuration file to supply the driver class name and driver
parameters to use when connecting to a database.
The following section of Java code shows how you might register
MySQL Connector/J from the main() method of your application. If
testing this code, first read the installation section at Chapter
3, "Connector/J Installation," to make sure you have connector
installed correctly and the CLASSPATH set up. Also, ensure that
MySQL is configured to accept external TCP/IP connections.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
// Notice, do not import com.mysql.jdbc.*
// or you will have problems!
public class LoadDriver {
public static void main(String[] args) {
try {
// The newInstance() call is a work around for some
// broken Java implementations
Class.forName("com.mysql.jdbc.Driver").newInstance();
} catch (Exception ex) {
// handle the error
}
}
}
After the driver has been registered with the DriverManager, you
can obtain a Connection instance that is connected to a particular
database by calling DriverManager.getConnection():
Example 6.1. Connector/J: Obtaining a connection from the
DriverManager
If you have not already done so, please review the section Section
6.1, "Connecting to MySQL Using the JDBC DriverManager Interface"
before working with these examples.
This example shows how you can obtain a Connection instance from
the DriverManager. There are a few different signatures for the
getConnection() method. Consult the API documentation that comes
with your JDK for more specific information on how to use them.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
Connection conn = null;
...
try {
conn =
DriverManager.getConnection("jdbc:mysql://localhost/test?" +
"user=monty&password=greatsqldb");
// Do something with the Connection
...
} catch (SQLException ex) {
// handle any errors
System.out.println("SQLException: " + ex.getMessage());
System.out.println("SQLState: " + ex.getSQLState());
System.out.println("VendorError: " + ex.getErrorCode());
}
Once a Connection is established, it can be used to create
Statement and PreparedStatement objects, as well as retrieve
metadata about the database. This is explained in the following
sections.
6.2. Using JDBC Statement Objects to Execute SQL
Statement objects allow you to execute basic SQL queries and
retrieve the results through the ResultSet class, which is
described later.
To create a Statement instance, you call the createStatement()
method on the Connection object you have retrieved using one of
the DriverManager.getConnection() or DataSource.getConnection()
methods described earlier.
Once you have a Statement instance, you can execute a SELECT
(http://dev.mysql.com/doc/refman/5.5/en/select.html) query by
calling the executeQuery(String) method with the SQL you want to
use.
To update data in the database, use the executeUpdate(String SQL)
method. This method returns the number of rows matched by the
update statement, not the number of rows that were modified.
If you do not know ahead of time whether the SQL statement will be
a SELECT (http://dev.mysql.com/doc/refman/5.5/en/select.html) or
an UPDATE
(http://dev.mysql.com/doc/refman/5.5/en/update.html)/INSERT
(http://dev.mysql.com/doc/refman/5.5/en/insert.html), then you can
use the execute(String SQL) method. This method will return true
if the SQL query was a SELECT
(http://dev.mysql.com/doc/refman/5.5/en/select.html), or false if
it was an UPDATE
(http://dev.mysql.com/doc/refman/5.5/en/update.html), INSERT
(http://dev.mysql.com/doc/refman/5.5/en/insert.html), or DELETE
(http://dev.mysql.com/doc/refman/5.5/en/delete.html) statement. If
the statement was a SELECT
(http://dev.mysql.com/doc/refman/5.5/en/select.html) query, you
can retrieve the results by calling the getResultSet() method. If
the statement was an UPDATE
(http://dev.mysql.com/doc/refman/5.5/en/update.html), INSERT
(http://dev.mysql.com/doc/refman/5.5/en/insert.html), or DELETE
(http://dev.mysql.com/doc/refman/5.5/en/delete.html) statement,
you can retrieve the affected rows count by calling
getUpdateCount() on the Statement instance.
Example 6.2. Connector/J: Using java.sql.Statement to execute a
SELECT query
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.ResultSet;
// assume that conn is an already created JDBC connection (see previo
us examples)
Statement stmt = null;
ResultSet rs = null;
try {
stmt = conn.createStatement();
rs = stmt.executeQuery("SELECT foo FROM bar");
// or alternatively, if you don't know ahead of time that
// the query will be a SELECT...
if (stmt.execute("SELECT foo FROM bar")) {
rs = stmt.getResultSet();
}
// Now do something with the ResultSet ....
}
catch (SQLException ex){
// handle any errors
System.out.println("SQLException: " + ex.getMessage());
System.out.println("SQLState: " + ex.getSQLState());
System.out.println("VendorError: " + ex.getErrorCode());
}
finally {
// it is a good idea to release
// resources in a finally{} block
// in reverse-order of their creation
// if they are no-longer needed
if (rs != null) {
try {
rs.close();
} catch (SQLException sqlEx) { } // ignore
rs = null;
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException sqlEx) { } // ignore
stmt = null;
}
}
6.3. Using JDBC CallableStatements to Execute Stored Procedures
Starting with MySQL server version 5.0 when used with Connector/J
3.1.1 or newer, the java.sql.CallableStatement interface is fully
implemented with the exception of the getParameterMetaData()
method.
For more information on MySQL stored procedures, please refer to
http://dev.mysql.com/doc/mysql/en/stored-routines.html.
Connector/J exposes stored procedure functionality through JDBC's
CallableStatement interface.
Note
Current versions of MySQL server do not return enough information
for the JDBC driver to provide result set metadata for callable
statements. This means that when using CallableStatement,
ResultSetMetaData may return NULL.
The following example shows a stored procedure that returns the
value of inOutParam incremented by 1, and the string passed in
using inputParam as a ResultSet:
Example 6.3. Connector/J: Calling Stored Procedures
CREATE PROCEDURE demoSp(IN inputParam VARCHAR(255), \
INOUT inOutParam INT)
BEGIN
DECLARE z INT;
SET z = inOutParam + 1;
SET inOutParam = z;
SELECT inputParam;
SELECT CONCAT('zyxw', inputParam);
END
To use the demoSp procedure with Connector/J, follow these steps:
1. Prepare the callable statement by using
Connection.prepareCall().
Notice that you have to use JDBC escape syntax, and that the
parentheses surrounding the parameter placeholders are not
optional:
Example 6.4. Connector/J: Using Connection.prepareCall()
import java.sql.CallableStatement;
...
//
// Prepare a call to the stored procedure 'demoSp'
// with two parameters
//
// Notice the use of JDBC-escape syntax ({call ...})
//
CallableStatement cStmt = conn.prepareCall("{call demoSp(?, ?)}")
;
cStmt.setString(1, "abcdefg");
Note
Connection.prepareCall() is an expensive method, due to the
metadata retrieval that the driver performs to support output
parameters. For performance reasons, minimize unnecessary
calls to Connection.prepareCall() by reusing CallableStatement
instances in your code.
2. Register the output parameters (if any exist)
To retrieve the values of output parameters (parameters
specified as OUT or INOUT when you created the stored
procedure), JDBC requires that they be specified before
statement execution using the various
registerOutputParameter() methods in the CallableStatement
interface:
Example 6.5. Connector/J: Registering output parameters
import java.sql.Types;
...
//
// Connector/J supports both named and indexed
// output parameters. You can register output
// parameters using either method, as well
// as retrieve output parameters using either
// method, regardless of what method was
// used to register them.
//
// The following examples show how to use
// the various methods of registering
// output parameters (you should of course
// use only one registration per parameter).
//
//
// Registers the second parameter as output, and
// uses the type 'INTEGER' for values returned from
// getObject()
//
cStmt.registerOutParameter(2, Types.INTEGER);
//
// Registers the named parameter 'inOutParam', and
// uses the type 'INTEGER' for values returned from
// getObject()
//
cStmt.registerOutParameter("inOutParam", Types.INTEGER);
...
3. Set the input parameters (if any exist)
Input and in/out parameters are set as for PreparedStatement
objects. However, CallableStatement also supports setting
parameters by name:
Example 6.6. Connector/J: Setting CallableStatement input
parameters
...
//
// Set a parameter by index
//
cStmt.setString(1, "abcdefg");
//
// Alternatively, set a parameter using
// the parameter name
//
cStmt.setString("inputParameter", "abcdefg");
//
// Set the 'in/out' parameter using an index
//
cStmt.setInt(2, 1);
//
// Alternatively, set the 'in/out' parameter
// by name
//
cStmt.setInt("inOutParam", 1);
...
4. Execute the CallableStatement, and retrieve any result sets or
output parameters.
Although CallableStatement supports calling any of the
Statement execute methods (executeUpdate(), executeQuery() or
execute()), the most flexible method to call is execute(), as
you do not need to know ahead of time if the stored procedure
returns result sets:
Example 6.7. Connector/J: Retrieving results and output
parameter values
...
boolean hadResults = cStmt.execute();
//
// Process all returned result sets
//
while (hadResults) {
ResultSet rs = cStmt.getResultSet();
// process result set
...
hadResults = cStmt.getMoreResults();
}
//
// Retrieve output parameters
//
// Connector/J supports both index-based and
// name-based retrieval
//
int outputValue = cStmt.getInt(2); // index-based
outputValue = cStmt.getInt("inOutParam"); // name-based
...
6.4. Retrieving AUTO_INCREMENT Column Values through JDBC
Before version 3.0 of the JDBC API, there was no standard way of
retrieving key values from databases that supported auto increment
or identity columns. With older JDBC drivers for MySQL, you could
always use a MySQL-specific method on the Statement interface, or
issue the query SELECT LAST_INSERT_ID() after issuing an INSERT
(http://dev.mysql.com/doc/refman/5.5/en/insert.html) to a table
that had an AUTO_INCREMENT key. Using the MySQL-specific method
call isn't portable, and issuing a SELECT
(http://dev.mysql.com/doc/refman/5.5/en/select.html) to get the
AUTO_INCREMENT key's value requires another round-trip to the
database, which isn't as efficient as possible. The following code
snippets demonstrate the three different ways to retrieve
AUTO_INCREMENT values. First, we demonstrate the use of the new
JDBC 3.0 method getGeneratedKeys() which is now the preferred
method to use if you need to retrieve AUTO_INCREMENT keys and have
access to JDBC 3.0. The second example shows how you can retrieve
the same value using a standard SELECT LAST_INSERT_ID() query. The
final example shows how updatable result sets can retrieve the
AUTO_INCREMENT value when using the insertRow() method.
Example 6.8. Connector/J: Retrieving AUTO_INCREMENT column values
using Statement.getGeneratedKeys()
Statement stmt = null;
ResultSet rs = null;
try {
//
// Create a Statement instance that we can use for
// 'normal' result sets assuming you have a
// Connection 'conn' to a MySQL database already
// available
stmt = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
java.sql.ResultSet.CONCUR_UPDATABLE);
//
// Issue the DDL queries for the table for this example
//
stmt.executeUpdate("DROP TABLE IF EXISTS autoIncTutorial");
stmt.executeUpdate(
"CREATE TABLE autoIncTutorial ("
+ "priKey INT NOT NULL AUTO_INCREMENT, "
+ "dataField VARCHAR(64), PRIMARY KEY (priKey))");
//
// Insert one row that will generate an AUTO INCREMENT
// key in the 'priKey' field
//
stmt.executeUpdate(
"INSERT INTO autoIncTutorial (dataField) "
+ "values ('Can I Get the Auto Increment Field?')",
Statement.RETURN_GENERATED_KEYS);
//
// Example of using Statement.getGeneratedKeys()
// to retrieve the value of an auto-increment
// value
//
int autoIncKeyFromApi = -1;
rs = stmt.getGeneratedKeys();
if (rs.next()) {
autoIncKeyFromApi = rs.getInt(1);
} else {
// throw an exception from here
}
rs.close();
rs = null;
System.out.println("Key returned from getGeneratedKeys():"
+ autoIncKeyFromApi);
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException ex) {
// ignore
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException ex) {
// ignore
}
}
}
Example 6.9. Connector/J: Retrieving AUTO_INCREMENT column values
using SELECT LAST_INSERT_ID()
Statement stmt = null;
ResultSet rs = null;
try {
//
// Create a Statement instance that we can use for
// 'normal' result sets.
stmt = conn.createStatement();
//
// Issue the DDL queries for the table for this example
//
stmt.executeUpdate("DROP TABLE IF EXISTS autoIncTutorial");
stmt.executeUpdate(
"CREATE TABLE autoIncTutorial ("
+ "priKey INT NOT NULL AUTO_INCREMENT, "
+ "dataField VARCHAR(64), PRIMARY KEY (priKey))");
//
// Insert one row that will generate an AUTO INCREMENT
// key in the 'priKey' field
//
stmt.executeUpdate(
"INSERT INTO autoIncTutorial (dataField) "
+ "values ('Can I Get the Auto Increment Field?')");
//
// Use the MySQL LAST_INSERT_ID()
// function to do the same thing as getGeneratedKeys()
//
int autoIncKeyFromFunc = -1;
rs = stmt.executeQuery("SELECT LAST_INSERT_ID()");
if (rs.next()) {
autoIncKeyFromFunc = rs.getInt(1);
} else {
// throw an exception from here
}
rs.close();
System.out.println("Key returned from " +
"'SELECT LAST_INSERT_ID()': " +
autoIncKeyFromFunc);
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException ex) {
// ignore
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException ex) {
// ignore
}
}
}
Example 6.10. Connector/J: Retrieving AUTO_INCREMENT column values
in Updatable ResultSets
Statement stmt = null;
ResultSet rs = null;
try {
//
// Create a Statement instance that we can use for
// 'normal' result sets as well as an 'updatable'
// one, assuming you have a Connection 'conn' to
// a MySQL database already available
//
stmt = conn.createStatement(java.sql.ResultSet.TYPE_FORWARD_ONLY,
java.sql.ResultSet.CONCUR_UPDATABLE);
//
// Issue the DDL queries for the table for this example
//
stmt.executeUpdate("DROP TABLE IF EXISTS autoIncTutorial");
stmt.executeUpdate(
"CREATE TABLE autoIncTutorial ("
+ "priKey INT NOT NULL AUTO_INCREMENT, "
+ "dataField VARCHAR(64), PRIMARY KEY (priKey))");
//
// Example of retrieving an AUTO INCREMENT key
// from an updatable result set
//
rs = stmt.executeQuery("SELECT priKey, dataField "
+ "FROM autoIncTutorial");
rs.moveToInsertRow();
rs.updateString("dataField", "AUTO INCREMENT here?");
rs.insertRow();
//
// the driver adds rows at the end
//
rs.last();
//
// We should now be on the row we just inserted
//
int autoIncKeyFromRS = rs.getInt("priKey");
rs.close();
rs = null;
System.out.println("Key returned for inserted row: "
+ autoIncKeyFromRS);
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException ex) {
// ignore
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException ex) {
// ignore
}
}
}
Running the preceding example code should produce the following
output:
Key returned from getGeneratedKeys(): 1
Key returned from SELECT LAST_INSERT_ID(): 1
Key returned for inserted row: 2
At times, it can be tricky to use the SELECT LAST_INSERT_ID()
query, as that function's value is scoped to a connection. So, if
some other query happens on the same connection, the value is
overwritten. On the other hand, the getGeneratedKeys() method is
scoped by the Statement instance, so it can be used even if other
queries happen on the same connection, but not on the same
Statement instance.
Chapter 7. Connection Pooling with Connector/J
Connection pooling is a technique of creating and managing a pool
of connections that are ready for use by any thread
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_thread)
that needs them. Connection pooling can greatly increase the
performance of your Java application, while reducing overall
resource usage.
How Connection Pooling Works
Most applications only need a thread to have access to a JDBC
connection when they are actively processing a transaction
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_transac
tion), which often takes only milliseconds to complete. When not
processing a transaction, the connection sits idle. Connection
pooling enables the idle connection to be used by some other
thread to do useful work.
In practice, when a thread needs to do work against a MySQL or
other database with JDBC, it requests a connection from the pool.
When the thread is finished using the connection, it returns it to
the pool, so that it can be used by any other threads.
When the connection is loaned out from the pool, it is used
exclusively by the thread that requested it. From a programming
point of view, it is the same as if your thread called
DriverManager.getConnection() every time it needed a JDBC
connection. With connection pooling, your thread may end up using
either a new connection or an already-existing connection.
Benefits of Connection Pooling
The main benefits to connection pooling are:
* Reduced connection creation time.
Although this is not usually an issue with the quick
connection setup that MySQL offers compared to other
databases, creating new JDBC connections still incurs
networking and JDBC driver overhead that will be avoided if
connections are recycled.
* Simplified programming model.
When using connection pooling, each individual thread can act
as though it has created its own JDBC connection, allowing you
to use straightforward JDBC programming techniques.
* Controlled resource usage.
If you create a new connection every time a thread needs one,
rather than using connection pooling, your application's
resource usage can be wasteful and lead to unpredictable
behavior under load.
Using Connection Pooling with Connector/J
Sun has standardized the concept of connection pooling in JDBC
through the JDBC 2.0 Optional interfaces, and all major
application servers have implementations of these APIs that work
with MySQL Connector/J.
Generally, you configure a connection pool in your application
server configuration files, and access it through the Java Naming
and Directory Interface (JNDI). The following code shows how you
might use a connection pool from an application deployed in a J2EE
application server:
Example 7.1. Connector/J: Using a connection pool with a J2EE
application server
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import javax.naming.InitialContext;
import javax.sql.DataSource;
public class MyServletJspOrEjb {
public void doSomething() throws Exception {
/*
* Create a JNDI Initial context to be able to
* lookup the DataSource
*
* In production-level code, this should be cached as
* an instance or static variable, as it can
* be quite expensive to create a JNDI context.
*
* Note: This code only works when you are using servlets
* or EJBs in a J2EE application server. If you are
* using connection pooling in standalone Java code, you
* will have to create/configure datasources using whatever
* mechanisms your particular connection pooling library
* provides.
*/
InitialContext ctx = new InitialContext();
/*
* Lookup the DataSource, which will be backed by a pool
* that the application server provides. DataSource instance
s
* are also a good candidate for caching as an instance
* variable, as JNDI lookups can be expensive as well.
*/
DataSource ds =
(DataSource)ctx.lookup("java:comp/env/jdbc/MySQLDB");
/*
* The following code is what would actually be in your
* Servlet, JSP or EJB 'service' method...where you need
* to work with a JDBC connection.
*/
Connection conn = null;
Statement stmt = null;
try {
conn = ds.getConnection();
/*
* Now, use normal JDBC programming to work with
* MySQL, making sure to close each resource when you're
* finished with it, which permits the connection pool
* resources to be recovered as quickly as possible
*/
stmt = conn.createStatement();
stmt.execute("SOME SQL QUERY");
stmt.close();
stmt = null;
conn.close();
conn = null;
} finally {
/*
* close any jdbc instances here that weren't
* explicitly closed during normal code path, so
* that we don't 'leak' resources...
*/
if (stmt != null) {
try {
stmt.close();
} catch (sqlexception sqlex) {
// ignore, as we can't do anything about it here
}
stmt = null;
}
if (conn != null) {
try {
conn.close();
} catch (sqlexception sqlex) {
// ignore, as we can't do anything about it here
}
conn = null;
}
}
}
}
When using connection pooling, always make sure that connections,
and anything created by them (such as statements or result sets)
are closed. This rule applies no matter what happens in your code
(exceptions, flow-of-control, and so forth). When these objects
are closed, they can be re-used; otherwise, they will be stranded,
which means that the MySQL server resources they represent (such
as buffers, locks, or sockets) are tied up for some time, or in
the worst case can be tied up forever.
Sizing the Connection Pool
Each connection to MySQL has overhead (memory, CPU, context
switches, and so forth) on both the client and server side. Every
connection limits how many resources there are available to your
application as well as the MySQL server. Many of these resources
will be used whether or not the connection is actually doing any
useful work! Connection pools can be tuned to maximize
performance, while keeping resource utilization below the point
where your application will start to fail rather than just run
slower.
The optimal size for the connection pool depends on anticipated
load and average database transaction time. In practice, the
optimal connection pool size can be smaller than you might expect.
If you take Sun's Java Petstore blueprint application for example,
a connection pool of 15-20 connections can serve a relatively
moderate load (600 concurrent users) using MySQL and Tomcat with
acceptable response times.
To correctly size a connection pool for your application, create
load test scripts with tools such as Apache JMeter or The Grinder,
and load test your application.
An easy way to determine a starting point is to configure your
connection pool's maximum number of connections to be unbounded,
run a load test, and measure the largest amount of concurrently
used connections. You can then work backward from there to
determine what values of minimum and maximum pooled connections
give the best performance for your particular application.
Validating Connections
MySQL Connector/J can validate the connection by executing a
lightweight ping against a server. In the case of load-balanced
connections, this is performed against all active pooled internal
connections that are retained. This is beneficial to Java
applications using connection pools, as the pool can use this
feature to validate connections. Depending on your connection pool
and configuration, this validation can be carried out at different
times:
1. Before the pool returns a connection to the application.
2. When the application returns a connection to the pool.
3. During periodic checks of idle connections.
To use this feature, specify a validation query in your connection
pool that starts with /* ping */. Note that the syntax must be
exactly as specified. This will cause the driver send a ping to
the server and return a dummy lightweight result set. When using a
ReplicationConnection or LoadBalancedConnection, the ping will be
sent across all active connections.
It is critical that the syntax be specified correctly. The syntax
needs to be exact for reasons of efficiency, as this test is done
for every statement that is executed:
protected static final String PING_MARKER = "/* ping */";
...
if (sql.charAt(0) == '/') {
if (sql.startsWith(PING_MARKER)) {
doPingInstead();
...
None of the following snippets will work, because the ping syntax
is sensitive to whitespace, capitalization, and placement:
sql = "/* PING */ SELECT 1";
sql = "SELECT 1 /* ping*/";
sql = "/*ping*/ SELECT 1";
sql = " /* ping */ SELECT 1";
sql = "/*to ping or not to ping*/ SELECT 1";
All of the previous statements will issue a normal SELECT
statement and will not be transformed into the lightweight ping.
Further, for load-balanced connections, the statement will be
executed against one connection in the internal pool, rather than
validating each underlying physical connection. This results in
the non-active physical connections assuming a stale state, and
they may die. If Connector/J then re-balances, it might select a
dead connection, resulting in an exception being passed to the
application. To help prevent this, you can use
loadBalanceValidateConnectionOnSwapServer to validate the
connection before use.
If your Connector/J deployment uses a connection pool that allows
you to specify a validation query, take advantage of it, but
ensure that the query starts exactly with /* ping */. This is
particularly important if you are using the load-balancing or
replication-aware features of Connector/J, as it will help keep
alive connections which otherwise will go stale and die, causing
problems later.
Chapter 8. Load Balancing with Connector/J
Connector/J has long provided an effective means to distribute
read/write load across multiple MySQL server instances for Cluster
or master-master replication deployments. Starting with
Connector/J 5.1.3, you can now dynamically configure load-balanced
connections, with no service outage. In-process transactions are
not lost, and no application exceptions are generated if any
application is trying to use that particular server instance.
There are two connection string options associated with this
functionality:
* loadBalanceConnectionGroup - This provides the ability to
group connections from different sources. This allows you to
manage these JDBC sources within a single class loader in any
combination you choose. If they use the same configuration,
and you want to manage them as a logical single group, give
them the same name. This is the key property for management:
if you do not define a name (string) for
loadBalanceConnectionGroup, you cannot manage the connections.
All load-balanced connections sharing the same
loadBalanceConnectionGroup value, regardless of how the
application creates them, will be managed together.
* loadBalanceEnableJMX - The ability to manage the connections
is exposed when you define a loadBalanceConnectionGroup, but
if you want to manage this externally, enable JMX by setting
this property to true. This enables a JMX implementation,
which exposes the management and monitoring operations of a
connection group. Further, start your application with the
-Dcom.sun.management.jmxremote JVM flag. You can then perform
connect and perform operations using a JMX client such as
jconsole.
Once a connection has been made using the correct connection
string options, a number of monitoring properties are available:
* Current active host count.
* Current active physical connection count.
* Current active logical connection count.
* Total logical connections created.
* Total transaction count.
The following management operations can also be performed:
* Add host.
* Remove host.
The JMX interface,
com.mysql.jdbc.jmx.LoadBalanceConnectionGroupManagerMBean, has the
following methods:
* int getActiveHostCount(String group);
* int getTotalHostCount(String group);
* long getTotalLogicalConnectionCount(String group);
* long getActiveLogicalConnectionCount(String group);
* long getActivePhysicalConnectionCount(String group);
* long getTotalPhysicalConnectionCount(String group);
* long getTotalTransactionCount(String group);
* void removeHost(String group, String host) throws
SQLException;
* void stopNewConnectionsToHost(String group, String host)
throws SQLException;
* void addHost(String group, String host, boolean forExisting);
* String getActiveHostsList(String group);
* String getRegisteredConnectionGroups();
The getRegisteredConnectionGroups() method returns the names of
all connection groups defined in that class loader.
You can test this setup with the following code:
public class Test {
private static String URL = "jdbc:mysql:loadbalance://" +
"localhost:3306,localhost:3310/test?" +
"loadBalanceConnectionGroup=first&loadBalanceEnableJMX=true";
public static void main(String[] args) throws Exception {
new Thread(new Repeater()).start();
new Thread(new Repeater()).start();
new Thread(new Repeater()).start();
}
static Connection getNewConnection() throws SQLException, ClassNo
tFoundException {
Class.forName("com.mysql.jdbc.Driver");
return DriverManager.getConnection(URL, "root", "");
}
static void executeSimpleTransaction(Connection c, int conn, int
trans){
try {
c.setAutoCommit(false);
Statement s = c.createStatement();
s.executeQuery("SELECT SLEEP(1) /* Connection: " + conn +
", transaction: " + trans + " */");
c.commit();
} catch (SQLException e) {
e.printStackTrace();
}
}
public static class Repeater implements Runnable {
public void run() {
for(int i=0; i < 100; i++){
try {
Connection c = getNewConnection();
for(int j=0; j < 10; j++){
executeSimpleTransaction(c, i, j);
Thread.sleep(Math.round(100 * Math.random()))
;
}
c.close();
Thread.sleep(100);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
}
After compiling, the application can be started with the
-Dcom.sun.management.jmxremote flag, to enable remote management.
jconsole can then be started. The Test main class will be listed
by jconsole. Select this and click Connect. You can then navigate
to the com.mysql.jdbc.jmx.LoadBalanceConnectionGroupManager bean.
At this point, you can click on various operations and examine the
returned result.
If you now had an additional instance of MySQL running on port
3309, you could ensure that Connector/J starts using it by using
the addHost(), which is exposed in jconsole. Note that these
operations can be performed dynamically without having to stop the
application running.
For further information on the combination of load balancing and
failover, see Chapter 9, "Failover with Connector/J."
Chapter 9. Failover with Connector/J
Connector/J provides a useful load-balancing implementation for
Cluster or multi-master deployments, as explained in Chapter 8,
"Load Balancing with Connector/J." As of Connector/J 5.1.12, this
same implementation is used for balancing load between read-only
slaves with ReplicationDriver. When trying to balance workload
between multiple servers, the driver has to determine when it is
safe to swap servers, doing so in the middle of a transaction, for
example, could cause problems. It is important not to lose state
information. For this reason, Connector/J will only try to pick a
new server when one of the following happens:
1. At transaction boundaries (transactions are explicitly
committed or rolled back).
2. A communication exception (SQL State starting with "08") is
encountered.
3. When a SQLException matches conditions defined by user, using
the extension points defined by the
loadBalanceSQLStateFailover,
loadBalanceSQLExceptionSubclassFailover or
loadBalanceExceptionChecker properties.
The third condition revolves around three new properties
introduced with Connector/J 5.1.13. It allows you to control which
SQLExceptions trigger failover.
* loadBalanceExceptionChecker - The loadBalanceExceptionChecker
property is really the key. This takes a fully-qualified class
name which implements the new
com.mysql.jdbc.LoadBalanceExceptionChecker interface. This
interface is very simple, and you only need to implement the
following method:
public boolean shouldExceptionTriggerFailover(SQLException ex)
A SQLException is passed in, and a boolean returned. A value
of true triggers a failover, false does not.
You can use this to implement your own custom logic. An
example where this might be useful is when dealing with
transient errors when using MySQL Cluster, where certain
buffers may become overloaded. The following code snippet
illustrates this:
public class NdbLoadBalanceExceptionChecker
extends StandardLoadBalanceExceptionChecker {
public boolean shouldExceptionTriggerFailover(SQLException ex) {
return super.shouldExceptionTriggerFailover(ex)
|| checkNdbException(ex);
}
private boolean checkNdbException(SQLException ex){
// Have to parse the message since most NDB errors
// are mapped to the same DEMC.
return (ex.getMessage().startsWith("Lock wait timeout exceeded") ||
(ex.getMessage().startsWith("Got temporary error")
&& ex.getMessage().endsWith("from NDB")));
}
}
The code above extends
com.mysql.jdbc.StandardLoadBalanceExceptionChecker, which is
the default implementation. There are a few convenient
shortcuts built into this, for those who want to have some
level of control using properties, without writing Java code.
This default implementation uses the two remaining properties:
loadBalanceSQLStateFailover and
loadBalanceSQLExceptionSubclassFailover.
* loadBalanceSQLStateFailover - allows you to define a
comma-delimited list of SQLState code prefixes, against which
a SQLException is compared. If the prefix matches, failover is
triggered. So, for example, the following would trigger a
failover if a given SQLException starts with "00", or is
"12345":
loadBalanceSQLStateFailover=00,12345
* loadBalanceSQLExceptionSubclassFailover - can be used in
conjunction with loadBalanceSQLStateFailover or on its own. If
you want certain subclasses of SQLException to trigger
failover, simply provide a comma-delimited list of
fully-qualified class or interface names to check against. For
example, if you want all SQLTransientConnectionExceptions to
trigger failover, you would specify:
loadBalanceSQLExceptionSubclassFailover=java.sql.SQLTransientConnecti
onException
While the three fail-over conditions enumerated earlier suit most
situations, if autocommit is enabled, Connector/J never
re-balances, and continues using the same physical connection.
This can be problematic, particularly when load-balancing is being
used to distribute read-only load across multiple slaves. However,
Connector/J can be configured to re-balance after a certain number
of statements are executed, when autocommit is enabled. This
functionality is dependent upon the following properties:
* loadBalanceAutoCommitStatementThreshold - defines the number
of matching statements which will trigger the driver to
potentially swap physical server connections. The default
value, 0, retains the behavior that connections with
autocommit enabled are never balanced.
* loadBalanceAutoCommitStatementRegex - the regular expression
against which statements must match. The default value, blank,
matches all statements. So, for example, using the following
properties will cause Connector/J to re-balance after every
third statement that contains the string "test":
loadBalanceAutoCommitStatementThreshold=3
loadBalanceAutoCommitStatementRegex=.*test.*
loadBalanceAutoCommitStatementRegex can prove useful in a
number of situations. Your application may use temporary
tables, server-side session state variables, or connection
state, where letting the driver arbitrarily swap physical
connections before processing is complete could cause data
loss or other problems. This allows you to identify a trigger
statement that is only executed when it is safe to swap
physical connections.
Chapter 10. Using the Connector/J Interceptor Classes
An interceptor is a software design pattern that provides a
transparent way to extend or modify some aspect of a program,
similar to a user exit. No recompiling is required. With
Connector/J, the interceptors are enabled and disabled by updating
the connection string to refer to different sets of interceptor
classes that you instantiate.
The connection properties that control the interceptors are
explained in Section 5.1, "Driver/Datasource Class Names, URL
Syntax and Configuration Properties for Connector/J:"
* connectionLifecycleInterceptors, where you specify the fully
qualified names of classes that implement the
com.mysql.jdbc.ConnectionLifecycleInterceptor interface. In
these kinds of interceptor classes, you might log events such
as rollbacks, measure the time between transaction start and
end, or count events such as calls to setAutoCommit().
* exceptionInterceptors, where you specify the fully qualified
names of classes that implement the
com.mysql.jdbc.ExceptionInterceptor interface. In these kinds
of interceptor classes, you might add extra diagnostic
information to exceptions that can have multiple causes or
indicate a problem with server settings. Because
exceptionInterceptors classes are only called when handling a
SQLException thrown from Connector/J code, they can be used
even in production deployments without substantial performance
overhead.
* statementInterceptors, where you specify the fully qualified
names of classes that implement the
com.mysql.jdbc.StatementInterceptorV2 interface. In these
kinds of interceptor classes, you might change or augment the
processing done by certain kinds of statements, such as
automatically checking for queried data in a memcached server,
rewriting slow queries, logging information about statement
execution, or route requests to remote servers.
Chapter 11. Using Connector/J with Tomcat
The following instructions are based on the instructions for
Tomcat-5.x, available at
http://tomcat.apache.org/tomcat-5.5-doc/jndi-datasource-examples-h
owto.html which is current at the time this document was written.
First, install the .jar file that comes with Connector/J in
$CATALINA_HOME/common/lib so that it is available to all
applications installed in the container.
Next, configure the JNDI DataSource by adding a declaration
resource to $CATALINA_HOME/conf/server.xml in the context that
defines your web application:
<Context ....>
...
<Resource name="jdbc/MySQLDB"
auth="Container"
type="javax.sql.DataSource"/>
<ResourceParams name="jdbc/MySQLDB">
<parameter>
<name>factory</name>
<value>org.apache.commons.dbcp.BasicDataSourceFactory</value>
</parameter>
<parameter>
<name>maxActive</name>
<value>10</value>
</parameter>
<parameter>
<name>maxIdle</name>
<value>5</value>
</parameter>
<parameter>
<name>validationQuery</name>
<value>SELECT 1</value>
</parameter>
<parameter>
<name>testOnBorrow</name>
<value>true</value>
</parameter>
<parameter>
<name>testWhileIdle</name>
<value>true</value>
</parameter>
<parameter>
<name>timeBetweenEvictionRunsMillis</name>
<value>10000</value>
</parameter>
<parameter>
<name>minEvictableIdleTimeMillis</name>
<value>60000</value>
</parameter>
<parameter>
<name>username</name>
<value>someuser</value>
</parameter>
<parameter>
<name>password</name>
<value>somepass</value>
</parameter>
<parameter>
<name>driverClassName</name>
<value>com.mysql.jdbc.Driver</value>
</parameter>
<parameter>
<name>url</name>
<value>jdbc:mysql://localhost:3306/test</value>
</parameter>
</ResourceParams>
</Context>
Note that Connector/J 5.1.3 introduced a facility whereby, rather
than use a validationQuery value of SELECT 1, it is possible to
use validationQuery with a value set to /* ping */. This sends a
ping to the server which then returns a fake result set. This is a
lighter weight solution. It also has the advantage that if using
ReplicationConnection or LoadBalancedConnection type connections,
the ping will be sent across all active connections. The following
XML snippet illustrates how to select this option:
<parameter>
<name>validationQuery</name>
<value>/* ping */</value>
</parameter>
Note that /* ping */ has to be specified exactly.
In general, follow the installation instructions that come with
your version of Tomcat, as the way you configure datasources in
Tomcat changes from time to time, and if you use the wrong syntax
in your XML file, you will most likely end up with an exception
similar to the following:
Error: java.sql.SQLException: Cannot load JDBC driver class 'null ' S
QL
state: null
Note that the auto-loading of drivers having the
META-INF/service/java.sql.Driver class in JDBC 4.0 causes an
improper undeployment of the Connector/J driver in Tomcat on
Windows. Namely, the Connector/J jar remains locked. This is an
initialization problem that is not related to the driver. The
possible workarounds, if viable, are as follows: use
"antiResourceLocking=true" as a Tomcat Context attribute, or
remove the META-INF/ directory.
Chapter 12. Using Connector/J with JBoss
These instructions cover JBoss-4.x. To make the JDBC driver
classes available to the application server, copy the .jar file
that comes with Connector/J to the lib directory for your server
configuration (which is usually called default). Then, in the same
configuration directory, in the subdirectory named deploy, create
a datasource configuration file that ends with -ds.xml, which
tells JBoss to deploy this file as a JDBC Datasource. The file
should have the following contents:
<datasources>
<local-tx-datasource>
<jndi-name>MySQLDB</jndi-name>
<connection-url>jdbc:mysql://localhost:3306/dbname</connectio
n-url>
<driver-class>com.mysql.jdbc.Driver</driver-class>
<user-name>user</user-name>
<password>pass</password>
<min-pool-size>5</min-pool-size>
<max-pool-size>20</max-pool-size>
<idle-timeout-minutes>5</idle-timeout-minutes>
<exception-sorter-class-name>
com.mysql.jdbc.integration.jboss.ExtendedMysqlExceptionSorter
</exception-sorter-class-name>
<valid-connection-checker-class-name>
com.mysql.jdbc.integration.jboss.MysqlValidConnectionChecker
</valid-connection-checker-class-name>
</local-tx-datasource>
</datasources>
Chapter 13. Using Connector/J with Spring
The Spring Framework is a Java-based application framework
designed for assisting in application design by providing a way to
configure components. The technique used by Spring is a well known
design pattern called Dependency Injection (see Inversion of
Control Containers and the Dependency Injection pattern
(http://www.martinfowler.com/articles/injection.html)). This
article will focus on Java-oriented access to MySQL databases with
Spring 2.0. For those wondering, there is a .NET port of Spring
appropriately named Spring.NET.
Spring is not only a system for configuring components, but also
includes support for aspect oriented programming (AOP). This is
one of the main benefits and the foundation for Spring's resource
and transaction management. Spring also provides utilities for
integrating resource management with JDBC and Hibernate.
For the examples in this section the MySQL world sample database
will be used. The first task is to set up a MySQL data source
through Spring. Components within Spring use the "bean"
terminology. For example, to configure a connection to a MySQL
server supporting the world sample database, you might use:
<util:map id="dbProps">
<entry key="db.driver" value="com.mysql.jdbc.Driver"/>
<entry key="db.jdbcurl" value="jdbc:mysql://localhost/world"/>
<entry key="db.username" value="myuser"/>
<entry key="db.password" value="mypass"/>
</util:map>
In the above example, we are assigning values to properties that
will be used in the configuration. For the datasource
configuration:
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSo
urce">
<property name="driverClassName" value="${db.driver}"/>
<property name="url" value="${db.jdbcurl}"/>
<property name="username" value="${db.username}"/>
<property name="password" value="${db.password}"/>
</bean>
The placeholders are used to provide values for properties of this
bean. This means that you can specify all the properties of the
configuration in one place instead of entering the values for each
property on each bean. We do, however, need one more bean to pull
this all together. The last bean is responsible for actually
replacing the placeholders with the property values.
<bean
class="org.springframework.beans.factory.config.PropertyPlaceholderC
onfigurer">
<property name="properties" ref="dbProps"/>
</bean>
Now that we have our MySQL data source configured and ready to go,
we write some Java code to access it. The example below will
retrieve three random cities and their corresponding country using
the data source we configured with Spring.
// Create a new application context. this processes the Spring config
ApplicationContext ctx =
new ClassPathXmlApplicationContext("ex1appContext.xml");
// Retrieve the data source from the application context
DataSource ds = (DataSource) ctx.getBean("dataSource");
// Open a database connection using Spring's DataSourceUtils
Connection c = DataSourceUtils.getConnection(ds);
try {
// retrieve a list of three random cities
PreparedStatement ps = c.prepareStatement(
"select City.Name as 'City', Country.Name as 'Country' " +
"from City inner join Country on City.CountryCode = Country.C
ode " +
"order by rand() limit 3");
ResultSet rs = ps.executeQuery();
while(rs.next()) {
String city = rs.getString("City");
String country = rs.getString("Country");
System.out.printf("The city %s is in %s%n", city, country);
}
} catch (SQLException ex) {
// something has failed and we print a stack trace to analyse the
error
ex.printStackTrace();
// ignore failure closing connection
try { c.close(); } catch (SQLException e) { }
} finally {
// properly release our connection
DataSourceUtils.releaseConnection(c, ds);
}
This is very similar to normal JDBC access to MySQL with the main
difference being that we are using DataSourceUtils instead of the
DriverManager to create the connection.
While it may seem like a small difference, the implications are
somewhat far reaching. Spring manages this resource in a way
similar to a container managed data source in a J2EE application
server. When a connection is opened, it can be subsequently
accessed in other parts of the code if it is synchronized with a
transaction. This makes it possible to treat different parts of
your application as transactional instead of passing around a
database connection.
13.1. Using JdbcTemplate
Spring makes extensive use of the Template method design pattern
(see Template Method Pattern
(http://en.wikipedia.org/wiki/Template_method_pattern)). Our
immediate focus will be on the JdbcTemplate and related classes,
specifically NamedParameterJdbcTemplate. The template classes
handle obtaining and releasing a connection for data access when
one is needed.
The next example shows how to use NamedParameterJdbcTemplate
inside of a DAO (Data Access Object) class to retrieve a random
city given a country code.
public class Ex2JdbcDao {
/**
* Data source reference which will be provided by Spring.
*/
private DataSource dataSource;
/**
* Our query to find a random city given a country code. Notice
* the ":country" parameter toward the end. This is called a
* named parameter.
*/
private String queryString = "select Name from City " +
"where CountryCode = :country order by rand() limit 1";
/**
* Retrieve a random city using Spring JDBC access classes.
*/
public String getRandomCityByCountryCode(String cntryCode) {
// A template that permits using queries with named paramete
rs
NamedParameterJdbcTemplate template =
new NamedParameterJdbcTemplate(dataSource);
// A java.util.Map is used to provide values for the paramet
ers
Map params = new HashMap();
params.put("country", cntryCode);
// We query for an Object and specify what class we are expe
cting
return (String)template.queryForObject(queryString, params,
String.class);
}
/**
* A JavaBean setter-style method to allow Spring to inject the da
ta source.
* @param dataSource
*/
public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}
}
The focus in the above code is on the getRandomCityByCountryCode()
method. We pass a country code and use the
NamedParameterJdbcTemplate to query for a city. The country code
is placed in a Map with the key "country", which is the parameter
is named in the SQL query.
To access this code, you need to configure it with Spring by
providing a reference to the data source.
<bean id="dao" class="code.Ex2JdbcDao">
<property name="dataSource" ref="dataSource"/>
</bean>
At this point, we can just grab a reference to the DAO from Spring
and call getRandomCityByCountryCode().
// Create the application context
ApplicationContext ctx =
new ClassPathXmlApplicationContext("ex2appContext.xml");
// Obtain a reference to our DAO
Ex2JdbcDao dao = (Ex2JdbcDao) ctx.getBean("dao");
String countryCode = "USA";
// Find a few random cities in the US
for(int i = 0; i < 4; ++i)
System.out.printf("A random city in %s is %s%n", countryCode,
dao.getRandomCityByCountryCode(countryCode));
This example shows how to use Spring's JDBC classes to completely
abstract away the use of traditional JDBC classes including
Connection and PreparedStatement.
13.2. Transactional JDBC Access
You might be wondering how we can add transactions into our code
if we do not deal directly with the JDBC classes. Spring provides
a transaction management package that not only replaces JDBC
transaction management, but also enables declarative transaction
management (configuration instead of code).
To use transactional database access, we will need to change the
storage engine of the tables in the world database. The downloaded
script explicitly creates MyISAM tables which do not support
transactional semantics. The InnoDB storage engine does support
transactions and this is what we will be using. We can change the
storage engine with the following statements.
ALTER TABLE City ENGINE=InnoDB;
ALTER TABLE Country ENGINE=InnoDB;
ALTER TABLE CountryLanguage ENGINE=InnoDB;
A good programming practice emphasized by Spring is separating
interfaces and implementations. What this means is that we can
create a Java interface and only use the operations on this
interface without any internal knowledge of what the actual
implementation is. We will let Spring manage the implementation
and with this it will manage the transactions for our
implementation.
First you create a simple interface:
public interface Ex3Dao {
Integer createCity(String name, String countryCode,
String district, Integer population);
}
This interface contains one method that will create a new city
record in the database and return the id of the new record. Next
you need to create an implementation of this interface.
public class Ex3DaoImpl implements Ex3Dao {
protected DataSource dataSource;
protected SqlUpdate updateQuery;
protected SqlFunction idQuery;
public Integer createCity(String name, String countryCode,
String district, Integer population) {
updateQuery.update(new Object[] { name, countryCode,
district, population });
return getLastId();
}
protected Integer getLastId() {
return idQuery.run();
}
}
You can see that we only operate on abstract query objects here
and do not deal directly with the JDBC API. Also, this is the
complete implementation. All of our transaction management will be
dealt with in the configuration. To get the configuration started,
we need to create the DAO.
<bean id="dao" class="code.Ex3DaoImpl">
<property name="dataSource" ref="dataSource"/>
<property name="updateQuery">...</property>
<property name="idQuery">...</property>
</bean>
Now you need to set up the transaction configuration. The first
thing you must do is create transaction manager to manage the data
source and a specification of what transaction properties are
required for the dao methods.
<bean id="transactionManager"
class="org.springframework.jdbc.datasource.DataSourceTransactionMan
ager">
<property name="dataSource" ref="dataSource"/>
</bean>
<tx:advice id="txAdvice" transaction-manager="transactionManager">
<tx:attributes>
<tx:method name="*"/>
</tx:attributes>
</tx:advice>
The preceding code creates a transaction manager that handles
transactions for the data source provided to it. The txAdvice uses
this transaction manager and the attributes specify to create a
transaction for all methods. Finally you need to apply this advice
with an AOP pointcut.
<aop:config>
<aop:pointcut id="daoMethods"
expression="execution(* code.Ex3Dao.*(..))"/>
<aop:advisor advice-ref="txAdvice" pointcut-ref="daoMethods"/>
</aop:config>
This basically says that all methods called on the Ex3Dao
interface will be wrapped in a transaction. To make use of this,
you only have to retrieve the dao from the application context and
call a method on the dao instance.
Ex3Dao dao = (Ex3Dao) ctx.getBean("dao");
Integer id = dao.createCity(name, countryCode, district, pop);
We can verify from this that there is no transaction management
happening in our Java code and it is all configured with Spring.
This is a very powerful notion and regarded as one of the most
beneficial features of Spring.
13.3. Connection Pooling with Spring
In many situations, such as web applications, there will be a
large number of small database transactions. When this is the
case, it usually makes sense to create a pool of database
connections available for web requests as needed. Although MySQL
does not spawn an extra process when a connection is made, there
is still a small amount of overhead to create and set up the
connection. Pooling of connections also alleviates problems such
as collecting large amounts of sockets in the TIME_WAIT state.
Setting up pooling of MySQL connections with Spring is as simple
as changing the data source configuration in the application
context. There are a number of configurations that we can use. The
first example is based on the Jakarta Commons DBCP library
(http://jakarta.apache.org/commons/dbcp/). The example below
replaces the source configuration that was based on
DriverManagerDataSource with DBCP's BasicDataSource.
<bean id="dataSource" destroy-method="close"
class="org.apache.commons.dbcp.BasicDataSource">
<property name="driverClassName" value="${db.driver}"/>
<property name="url" value="${db.jdbcurl}"/>
<property name="username" value="${db.username}"/>
<property name="password" value="${db.password}"/>
<property name="initialSize" value="3"/>
</bean>
The configuration of the two solutions is very similar. The
difference is that DBCP will pool connections to the database
instead of creating a new connection every time one is requested.
We have also set a parameter here called initialSize. This tells
DBCP that we want three connections in the pool when it is
created.
Another way to configure connection pooling is to configure a data
source in our J2EE application server. Using JBoss as an example,
you can set up the MySQL connection pool by creating a file called
mysql-local-ds.xml and placing it in the server/default/deploy
directory in JBoss. Once we have this setup, we can use JNDI to
look it up. With Spring, this lookup is very simple. The data
source configuration looks like this.
<jee:jndi-lookup id="dataSource" jndi-name="java:MySQL_DS"/>
Chapter 14. Using Connector/J with GlassFish
This section explains how to use MySQL Connector/J with Glassfish
(tm) Server Open Source Edition 3.0.1. Glassfish can be downloaded
from the Glassfish website
(https://glassfish.dev.java.net/public/downloadsindex.html#top).
Once Glassfish is installed you will need to make sure it can
access MySQL Connector/J. To do this copy the MySQL Connector/J
JAR file to the directory GLASSFISH_INSTALL/glassfish/lib. For
example, copy mysql-connector-java-5.1.12-bin.jar to
C:\glassfishv3\glassfish\lib. Restart the Glassfish Application
Server.
You are now ready to create JDBC Connection Pools and JDBC
Resources.
Creating a Connection Pool
1. In the Glassfish Administration Console, using the navigation
tree navigate to Resources, JDBC, Connection Pools.
2. In the JDBC Connection Pools frame click New. You will enter a
two step wizard.
3. In the Name field under General Settings enter the name for
the connection pool, for example enter MySQLConnPool.
4. In the Resource Type field, select javax.sql.DataSource from
the drop-down listbox.
5. In the Database Vendor field, select MySQL from the drop-down
listbox. Click Next to go to the next page of the wizard.
6. You can accept the default settings for General Settings, Pool
Settings and Transactions for this example. Scroll down to
Additional Properties.
7. In Additional Properties you will need to ensure the following
properties are set:
+ ServerName - The server to connect to. For local testing
this will be localhost.
+ User - The user name with which to connect to MySQL.
+ Password - The corresponding password for the user.
+ DatabaseName - The database to connect to, for example
the sample MySQL database World.
8. Click Finish to exit the wizard. You will be taken to the JDBC
Connection Pools page where all current connection pools,
including the one you just created, will be displayed.
9. In the JDBC Connection Pools frame click on the connection
pool you just created. Here you can review and edit
information about the connection pool.
10. To test your connection pool click the Ping button at the top
of the frame. A message will be displayed confirming correct
operation or otherwise. If an error message is received
recheck the previous steps, and ensure that MySQL Connector/J
has been correctly copied into the previously specified
location.
Now that you have created a connection pool you will also need to
create a JDBC Resource (data source) for use by your application.
Creating a JDBC Resource
Your Java application will usually reference a data source object
to establish a connection with the database. This needs to be
created first using the following procedure.
* Using the navigation tree in the Glassfish Administration
Console, navigate to Resources, JDBC, JDBC Resources. A list
of resources will be displayed in the JDBC Resources frame.
* Click New. The New JDBC Resource frame will be displayed.
* In the JNDI Name field, enter the JNDI name that will be used
to access this resource, for example enter
jdbc/MySQLDataSource.
* In the Pool Name field, select a connection pool you want this
resource to use from the drop-down listbox.
* Optionally, you can enter a description into the Description
field.
* Additional properties can be added if required.
* Click OK to create the new JDBC resource. The JDBC Resources
frame will list all available JDBC Resources.
14.1. A Simple JSP Application with Glassfish, Connector/J and MySQL
This section shows how to deploy a simple JSP application on
Glassfish, that connects to a MySQL database.
This example assumes you have already set up a suitable Connection
Pool and JDBC Resource, as explained in the preceding sections. It
is also assumed you have a sample database installed, such as
world.
The main application code, index.jsp is presented here:
<%@ page import="java.sql.*, javax.sql.*, java.io.*, javax.naming.*"
%>
<html>
<head><title>Hello world from JSP</title></head>
<body>
<%
InitialContext ctx;
DataSource ds;
Connection conn;
Statement stmt;
ResultSet rs;
try {
ctx = new InitialContext();
ds = (DataSource) ctx.lookup("java:comp/env/jdbc/MySQLDataSource"
);
//ds = (DataSource) ctx.lookup("jdbc/MySQLDataSource");
conn = ds.getConnection();
stmt = conn.createStatement();
rs = stmt.executeQuery("SELECT * FROM Country");
while(rs.next()) {
%>
<h3>Name: <%= rs.getString("Name") %></h3>
<h3>Population: <%= rs.getString("Population") %></h3>
<%
}
}
catch (SQLException se) {
%>
<%= se.getMessage() %>
<%
}
catch (NamingException ne) {
%>
<%= ne.getMessage() %>
<%
}
%>
</body>
</html>
In addition two XML files are required: web.xml, and sun-web.xml.
There may be other files present, such as classes and images.
These files are organized into the directory structure as follows:
index.jsp
WEB-INF
|
- web.xml
- sun-web.xml
The code for web.xml is:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:
xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="h
ttp://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-ap
p_2_4.xsd">
<display-name>HelloWebApp</display-name>
<distributable/>
<resource-ref>
<res-ref-name>jdbc/MySQLDataSource</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
<res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>
</web-app>
The code for sun-web.xml is:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sun-web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Applicat
ion Server 8.1 Servlet 2.4//EN" "http://www.sun.com/software/appserve
r/dtds/sun-web-app_2_4-1.dtd">
<sun-web-app>
<context-root>HelloWebApp</context-root>
<resource-ref>
<res-ref-name>jdbc/MySQLDataSource</res-ref-name>
<jndi-name>jdbc/MySQLDataSource</jndi-name>
</resource-ref>
</sun-web-app>
These XML files illustrate a very important aspect of running JDBC
applications on Glassfish. On Glassfish it is important to map the
string specified for a JDBC resource to its JNDI name, as set up
in the Glassfish administration console. In this example, the JNDI
name for the JDBC resource, as specified in the Glassfish
Administration console when creating the JDBC Resource, was
jdbc/MySQLDataSource. This must be mapped to the name given in the
application. In this example the name specified in the
application, jdbc/MySQLDataSource, and the JNDI name, happen to be
the same, but this does not necessarily have to be the case. Note
that the XML element <res-ref-name> is used to specify the name as
used in the application source code, and this is mapped to the
JNDI name specified using the <jndi-name> element, in the file
sun-web.xml. The resource also has to be created in the web.xml
file, although the mapping of the resource to a JNDI name takes
place in the sun-web.xml file.
If you do not have this mapping set up correctly in the XML files
you will not be able to lookup the data source using a JNDI lookup
string such as:
ds = (DataSource) ctx.lookup("java:comp/env/jdbc/MySQLDataSource");
You will still be able to access the data source directly using:
ds = (DataSource) ctx.lookup("jdbc/MySQLDataSource");
With the source files in place, in the correct directory
structure, you are ready to deploy the application:
1. In the navigation tree, navigate to Applications - the
Applications frame will be displayed. Click Deploy.
2. You can now deploy an application packaged into a single WAR
file from a remote client, or you can choose a packaged file
or directory that is locally accessible to the server. If you
are simply testing an application locally you can simply point
Glassfish at the directory that contains your application,
without needing to package the application into a WAR file.
3. Now select the application type from the Type drop-down
listbox, which in this example is Web application.
4. Click OK.
Now, when you navigate to the Applications frame, you will have
the option to Launch, Redeploy, or Restart your application. You
can test your application by clicking Launch. The application will
connection to the MySQL database and display the Name and
Population of countries in the Country table.
14.2. A Simple Servlet with Glassfish, Connector/J and MySQL
This section describes a simple servlet that can be used in the
Glassfish environment to access a MySQL database. As with the
previous section, this example assumes the sample database world
is installed.
The project is set up with the following directory structure:
index.html
WEB-INF
|
- web.xml
- sun-web.xml
- classes
|
- HelloWebServlet.java
- HelloWebServlet.class
The code for the servlet, located in HelloWebServlet.java, is as
follows:
import javax.servlet.http.*;
import javax.servlet.*;
import java.io.*;
import java.sql.*;
import javax.sql.*;
import javax.naming.*;
public class HelloWebServlet extends HttpServlet {
InitialContext ctx = null;
DataSource ds = null;
Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
String sql = "SELECT Name, Population FROM Country WHERE Name=?";
public void init () throws ServletException {
try {
ctx = new InitialContext();
ds = (DataSource) ctx.lookup("java:comp/env/jdbc/MySQLDataSourc
e");
conn = ds.getConnection();
ps = conn.prepareStatement(sql);
}
catch (SQLException se) {
System.out.println("SQLException: "+se.getMessage());
}
catch (NamingException ne) {
System.out.println("NamingException: "+ne.getMessage());
}
}
public void destroy () {
try {
if (rs != null)
rs.close();
if (ps != null)
ps.close();
if (conn != null)
conn.close();
if (ctx != null)
ctx.close();
}
catch (SQLException se) {
System.out.println("SQLException: "+se.getMessage());
}
catch (NamingException ne) {
System.out.println("NamingException: "+ne.getMessage());
}
}
public void doPost(HttpServletRequest req, HttpServletResponse resp
){
try {
String country_name = req.getParameter("country_name");
resp.setContentType("text/html");
PrintWriter writer = resp.getWriter();
writer.println("<html><body>");
writer.println("<p>Country: "+country_name+"</p>");
ps.setString(1, country_name);
rs = ps.executeQuery();
if (!rs.next()){
writer.println("<p>Country does not exist!</p>");
}
else {
rs.beforeFirst();
while(rs.next()) {
writer.println("<p>Name: "+rs.getString("Name")+"</p>");
writer.println("<p>Population: "+rs.getString("Population")
+"</p>");
}
}
writer.println("</body></html>");
writer.close();
}
catch (Exception e) {
e.printStackTrace();
}
}
public void doGet(HttpServletRequest req, HttpServletResponse resp)
{
try {
resp.setContentType("text/html");
PrintWriter writer = resp.getWriter();
writer.println("<html><body>");
writer.println("<p>Hello from servlet doGet()</p>");
writer.println("</body></html>");
writer.close();
}
catch (Exception e) {
e.printStackTrace();
}
}
}
In the preceding code a basic doGet() method is implemented, but
is not used in the example. The code to establish the connection
with the database is as shown in the previous example, Section
14.1, "A Simple JSP Application with Glassfish, Connector/J and
MySQL," and is most conveniently located in the servlet init()
method. The corresponding freeing of resources is located in the
destroy method. The main functionality of the servlet is located
in the doPost() method. If the user enters nto the input form a
country name that can be located in the database, the population
of the country is returned. The code is invoked using a POST
action associated with the input form. The form is defined in the
file index.html:
<html>
<head><title>HelloWebServlet</title></head>
<body>
<h1>HelloWebServlet</h1>
<p>Please enter country name:</p>
<form action="HelloWebServlet" method="POST">
<input type="text" name="country_name" length="50" />
<input type="submit" value="Submit" />
</form>
</body>
</html>
The XML files web.xml and sun-web.xml are as for the example in
the preceding section, Section 14.1, "A Simple JSP Application
with Glassfish, Connector/J and MySQL," no additional changes are
required.
Whe compiling the Java source code, you will need to specify the
path to the file javaee.jar. On Windows, this can be done as
follows:
shell> javac -classpath c:\glassfishv3\glassfish\lib\javaee.jar Hello
WebServlet.java
Once the code is correctly located within its directory structure,
and compiled, the application can be deployed in Glassfish. This
is done in exactly the same way as described in the preceding
section, Section 14.1, "A Simple JSP Application with Glassfish,
Connector/J and MySQL."
Once deployed the application can be launched from within the
Glassfish Administration Console. Enter a country name such as
"England", and the application will return "Country does not
exist!". Enter "France", and the application will return a
population of 59225700.
Chapter 15. Troubleshooting Connector/J Applications
This section explains the symptoms and resolutions for the most
commonly encountered issues with applications using MySQL
Connector/J.
Questions
* 15.1: When I try to connect to the database with MySQL
Connector/J, I get the following exception:
SQLException: Server configuration denies access to data source
SQLState: 08001
VendorError: 0
* 15.2: My application throws an SQLException 'No Suitable
Driver'. Why is this happening?
* 15.3: I'm trying to use MySQL Connector/J in an applet or
application and I get an exception similar to:
SQLException: Cannot connect to MySQL server on host:3306.
Is there a MySQL server running on the machine/port you
are trying to connect to?
(java.security.AccessControlException)
SQLState: 08S01
VendorError: 0
* 15.4: I have a servlet/application that works fine for a day,
and then stops working overnight
* 15.5: I'm trying to use JDBC 2.0 updatable result sets, and I
get an exception saying my result set is not updatable.
* 15.6: I cannot connect to the MySQL server using Connector/J,
and I'm sure the connection parameters are correct.
* 15.7: I am trying to connect to my MySQL server within my
application, but I get the following error and stack trace:
java.net.SocketException
MESSAGE: Software caused connection abort: recv failed
STACKTRACE:
java.net.SocketException: Software caused connection abort: recv fail
ed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(Unknown Source)
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1392)
at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:1414)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:625)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:1926)
at com.mysql.jdbc.Connection.<init>(Connection.java:452)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.j
ava:411)
* 15.8: My application is deployed through JBoss and I am using
transactions to handle the statements on the MySQL database.
Under heavy loads, I am getting an error and stack trace, but
these only occur after a fixed period of heavy activity.
* 15.9: When using gcj, a java.io.CharConversionException
exception is raised when working with certain character
sequences.
* 15.10: Updating a table that contains a primary key
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_pri
mary_key) that is either FLOAT
(http://dev.mysql.com/doc/refman/5.5/en/floating-point-types.h
tml) or compound primary key that uses FLOAT
(http://dev.mysql.com/doc/refman/5.5/en/floating-point-types.h
tml) fails to update the table and raises an exception.
* 15.11: You get an ER_NET_PACKET_TOO_LARGE
(http://dev.mysql.com/doc/refman/5.5/en/error-messages-server.
html#error_er_net_packet_too_large) exception, even though the
binary blob size you want to insert using JDBC is safely below
the max_allowed_packet
(http://dev.mysql.com/doc/refman/5.5/en/server-system-variable
s.html#sysvar_max_allowed_packet) size.
* 15.12: What should you do if you receive error messages
similar to the following: "Communications link failure - Last
packet sent to the server was X ms ago"?
* 15.13: Why does Connector/J not reconnect to MySQL and
re-issue the statement after a communication failure, instead
of throwing an Exception, even though I use the autoReconnect
connection string option?
* 15.14: How can I use 3-byte UTF8 with Connector/J?
* 15.15: How can I use 4-byte UTF8, utf8mb4 with Connector/J?
* 15.16: Using useServerPrepStmts=false and certain character
encodings can lead to corruption when inserting BLOBs. How can
this be avoided?
Questions and Answers
15.1: When I try to connect to the database with MySQL
Connector/J, I get the following exception:
SQLException: Server configuration denies access to data source
SQLState: 08001
VendorError: 0
MySQL Connector/J must use TCP/IP sockets to connect to MySQL, as
Java does not support Unix Domain Sockets. Therefore, when MySQL
Connector/J connects to MySQL, the security manager in MySQL
server will use its grant tables to determine whether the
connection is permitted.
You must add the necessary security credentials to the MySQL
server for this to happen, using the GRANT
(http://dev.mysql.com/doc/refman/5.5/en/grant.html) statement to
your MySQL Server. See GRANT Syntax
(http://dev.mysql.com/doc/refman/5.5/en/grant.html), for more
information.
Note
Testing your connectivity with the mysql command-line client will
not work unless you add the "host" flag, and use something other
than localhost for the host. The mysql command-line client will
use Unix domain sockets if you use the special host name
localhost. If you are testing connectivity to localhost, use
127.0.0.1 as the host name instead.
Warning
Changing privileges and permissions improperly in MySQL can
potentially cause your server installation to not have optimal
security properties.
15.2: My application throws an SQLException 'No Suitable Driver'.
Why is this happening?
There are three possible causes for this error:
* The Connector/J driver is not in your CLASSPATH, see Chapter
3, "Connector/J Installation."
* The format of your connection URL is incorrect, or you are
referencing the wrong JDBC driver.
* When using DriverManager, the jdbc.drivers system property has
not been populated with the location of the Connector/J
driver.
15.3: I'm trying to use MySQL Connector/J in an applet or
application and I get an exception similar to:
SQLException: Cannot connect to MySQL server on host:3306.
Is there a MySQL server running on the machine/port you
are trying to connect to?
(java.security.AccessControlException)
SQLState: 08S01
VendorError: 0
Either you're running an Applet, your MySQL server has been
installed with the "skip-networking" option set, or your MySQL
server has a firewall sitting in front of it.
Applets can only make network connections back to the machine that
runs the web server that served the .class files for the applet.
This means that MySQL must run on the same machine (or you must
have some sort of port re-direction) for this to work. This also
means that you will not be able to test applets from your local
file system, you must always deploy them to a web server.
MySQL Connector/J can only communicate with MySQL using TCP/IP, as
Java does not support Unix domain sockets. TCP/IP communication
with MySQL might be affected if MySQL was started with the
"skip-networking" flag, or if it is firewalled.
If MySQL has been started with the "skip-networking" option set
(the Debian Linux package of MySQL server does this for example),
you need to comment it out in the file /etc/mysql/my.cnf or
/etc/my.cnf. Of course your my.cnf file might also exist in the
data directory of your MySQL server, or anywhere else (depending
on how MySQL was compiled for your system). Binaries created by us
always look in /etc/my.cnf and datadir/my.cnf. If your MySQL
server has been firewalled, you will need to have the firewall
configured to allow TCP/IP connections from the host where your
Java code is running to the MySQL server on the port that MySQL is
listening to (by default, 3306).
15.4: I have a servlet/application that works fine for a day, and
then stops working overnight
MySQL closes connections after 8 hours of inactivity. You either
need to use a connection pool that handles stale connections or
use the autoReconnect parameter (see Section 5.1,
"Driver/Datasource Class Names, URL Syntax and Configuration
Properties for Connector/J").
Also, catch SQLExceptions in your application and deal with them,
rather than propagating them all the way until your application
exits. This is just good programming practice. MySQL Connector/J
will set the SQLState (see java.sql.SQLException.getSQLState() in
your API docs) to 08S01 when it encounters network-connectivity
issues during the processing of a query. Attempt to reconnect to
MySQL at this point.
The following (simplistic) example shows what code that can handle
these exceptions might look like:
Example 15.1. Connector/J: Example of transaction with retry logic
public void doBusinessOp() throws SQLException {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
//
// How many times do you want to retry the transaction
// (or at least _getting_ a connection)?
//
int retryCount = 5;
boolean transactionCompleted = false;
do {
try {
conn = getConnection(); // assume getting this from a
// javax.sql.DataSource, or the
// java.sql.DriverManager
conn.setAutoCommit(false);
//
// Okay, at this point, the 'retry-ability' of the
// transaction really depends on your application logic,
// whether or not you're using autocommit (in this case
// not), and whether you're using transactional storage
// engines
//
// For this example, we'll assume that it's _not_ safe
// to retry the entire transaction, so we set retry
// count to 0 at this point
//
// If you were using exclusively transaction-safe tables,
// or your application could recover from a connection go
ing
// bad in the middle of an operation, then you would not
// touch 'retryCount' here, and just let the loop repeat
// until retryCount == 0.
//
retryCount = 0;
stmt = conn.createStatement();
String query = "SELECT foo FROM bar ORDER BY baz";
rs = stmt.executeQuery(query);
while (rs.next()) {
}
rs.close();
rs = null;
stmt.close();
stmt = null;
conn.commit();
conn.close();
conn = null;
transactionCompleted = true;
} catch (SQLException sqlEx) {
//
// The two SQL states that are 'retry-able' are 08S01
// for a communications error, and 40001 for deadlock.
//
// Only retry if the error was due to a stale connection,
// communications problem or deadlock
//
String sqlState = sqlEx.getSQLState();
if ("08S01".equals(sqlState) || "40001".equals(sqlState))
{
retryCount -= 1;
} else {
retryCount = 0;
}
} finally {
if (rs != null) {
try {
rs.close();
} catch (SQLException sqlEx) {
// You'd probably want to log this...
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException sqlEx) {
// You'd probably want to log this as well...
}
}
if (conn != null) {
try {
//
// If we got here, and conn is not null, the
// transaction should be rolled back, as not
// all work has been done
try {
conn.rollback();
} finally {
conn.close();
}
} catch (SQLException sqlEx) {
//
// If we got an exception here, something
// pretty serious is going on, so we better
// pass it up the stack, rather than just
// logging it...
throw sqlEx;
}
}
}
} while (!transactionCompleted && (retryCount > 0));
}
Note
Use of the autoReconnect option is not recommended because there
is no safe method of reconnecting to the MySQL server without
risking some corruption of the connection state or database state
information. Instead, use a connection pool, which will enable
your application to connect to the MySQL server using an available
connection from the pool. The autoReconnect facility is
deprecated, and may be removed in a future release.
15.5: I'm trying to use JDBC 2.0 updatable result sets, and I get
an exception saying my result set is not updatable.
Because MySQL does not have row identifiers, MySQL Connector/J can
only update result sets that have come from queries on tables that
have at least one primary key
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_primary
_key), the query must select every primary key column, and the
query can only span one table (that is, no joins). This is
outlined in the JDBC specification.
Note that this issue only occurs when using updatable result sets,
and is caused because Connector/J is unable to guarantee that it
can identify the correct rows within the result set to be updated
without having a unique reference to each row. There is no
requirement to have a unique field on a table if you are using
UPDATE (http://dev.mysql.com/doc/refman/5.5/en/update.html) or
DELETE (http://dev.mysql.com/doc/refman/5.5/en/delete.html)
statements on a table where you can individually specify the
criteria to be matched using a WHERE clause.
15.6: I cannot connect to the MySQL server using Connector/J, and
I'm sure the connection parameters are correct.
Make sure that the skip-networking
(http://dev.mysql.com/doc/refman/5.5/en/server-options.html#option
_mysqld_skip-networking) option has not been enabled on your
server. Connector/J must be able to communicate with your server
over TCP/IP; named sockets are not supported. Also ensure that you
are not filtering connections through a firewall or other network
security system. For more information, see Can't connect to
[local] MySQL server
(http://dev.mysql.com/doc/refman/5.5/en/can-not-connect-to-server.
html).
15.7: I am trying to connect to my MySQL server within my
application, but I get the following error and stack trace:
java.net.SocketException
MESSAGE: Software caused connection abort: recv failed
STACKTRACE:
java.net.SocketException: Software caused connection abort: recv fail
ed
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(Unknown Source)
at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1392)
at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:1414)
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:625)
at com.mysql.jdbc.Connection.createNewIO(Connection.java:1926)
at com.mysql.jdbc.Connection.<init>(Connection.java:452)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.j
ava:411)
The error probably indicates that you are using a older version of
the Connector/J JDBC driver (2.0.14 or 3.0.x) and you are trying
to connect to a MySQL server with version 4.1x or newer. The older
drivers are not compatible with 4.1 or newer of MySQL as they do
not support the newer authentication mechanisms.
It is likely that the older version of the Connector/J driver
exists within your application directory or your CLASSPATH
includes the older Connector/J package.
15.8: My application is deployed through JBoss and I am using
transactions to handle the statements on the MySQL database. Under
heavy loads, I am getting an error and stack trace, but these only
occur after a fixed period of heavy activity.
This is a JBoss, not Connector/J, issue and is connected to the
use of transactions. Under heavy loads the time taken for
transactions to complete can increase, and the error is caused
because you have exceeded the predefined timeout.
You can increase the timeout value by setting the
TransactionTimeout attribute to the TransactionManagerService
within the /conf/jboss-service.xml file (pre-4.0.3) or
/deploy/jta-service.xml for JBoss 4.0.3 or later. See
TransactionTimeout
(http://wiki.jboss.org/wiki/Wiki.jsp?page=TransactionTimeout)
within the JBoss wiki for more information.
15.9: When using gcj, a java.io.CharConversionException exception
is raised when working with certain character sequences.
This is a known issue with gcj which raises an exception when it
reaches an unknown character or one it cannot convert. Add
useJvmCharsetConverters=true to your connection string to force
character conversion outside of the gcj libraries, or try a
different JDK.
15.10: Updating a table that contains a primary key
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_primary
_key) that is either FLOAT
(http://dev.mysql.com/doc/refman/5.5/en/floating-point-types.html)
or compound primary key that uses FLOAT
(http://dev.mysql.com/doc/refman/5.5/en/floating-point-types.html)
fails to update the table and raises an exception.
Connector/J adds conditions to the WHERE clause during an UPDATE
(http://dev.mysql.com/doc/refman/5.5/en/update.html) to check the
old values of the primary key. If there is no match, then
Connector/J considers this a failure condition and raises an
exception.
The problem is that rounding differences between supplied values
and the values stored in the database may mean that the values
never match, and hence the update fails. The issue will affect all
queries, not just those from Connector/J.
To prevent this issue, use a primary key that does not use FLOAT
(http://dev.mysql.com/doc/refman/5.5/en/floating-point-types.html)
. If you have to use a floating point column in your primary key,
use DOUBLE
(http://dev.mysql.com/doc/refman/5.5/en/floating-point-types.html)
or DECIMAL
(http://dev.mysql.com/doc/refman/5.5/en/fixed-point-types.html)
types in place of FLOAT
(http://dev.mysql.com/doc/refman/5.5/en/floating-point-types.html)
.
15.11: You get an ER_NET_PACKET_TOO_LARGE
(http://dev.mysql.com/doc/refman/5.5/en/error-messages-server.html
#error_er_net_packet_too_large) exception, even though the binary
blob size you want to insert using JDBC is safely below the
max_allowed_packet
(http://dev.mysql.com/doc/refman/5.5/en/server-system-variables.ht
ml#sysvar_max_allowed_packet) size.
This is because the hexEscapeBlock() method in
com.mysql.jdbc.PreparedStatement.streamToBytes() may almost double
the size of your data.
15.12: What should you do if you receive error messages similar to
the following: "Communications link failure - Last packet sent to
the server was X ms ago"?
Generally speaking, this error suggests that the network
connection has been closed. There can be several root causes:
* Firewalls or routers may clamp down on idle connections (the
MySQL client/server protocol does not ping).
* The MySQL Server may be closing idle connections that exceed
the wait_timeout or interactive_timeout threshold.
To help troubleshoot these issues, the following tips can be used.
If a recent (5.1.13+) version of Connector/J is used, you will see
an improved level of information compared to earlier versions.
Older versions simply display the last time a packet was sent to
the server, which is frequently 0 ms ago. This is of limited use,
as it may be that a packet was just sent, while a packet from the
server has not been received for several hours. Knowing the period
of time since Connector/J last received a packet from the server
is useful information, so if this is not displayed in your
exception message, it is recommended that you update Connector/J.
Further, if the time a packet was last sent/received exceeds the
wait_timeout or interactive_timeout threshold, this is noted in
the exception message.
Although network connections can be volatile, the following can be
helpful in avoiding problems:
* Ensure connections are valid when used from the connection
pool. Use a query that starts with /* ping */ to execute a
lightweight ping instead of full query. Note, the syntax of
the ping needs to be exactly as specified here.
* Minimize the duration a connection object is left idle while
other application logic is executed.
* Explicitly validate the connection before using it if the
connection has been left idle for an extended period of time.
* Ensure that wait_timeout and interactive_timeout are set
sufficiently high.
* Ensure that tcpKeepalive is enabled.
* Ensure that any configurable firewall or router timeout
settings allow for the maximum expected connection idle time.
Note
Do not expect to be able to reuse a connection without problems,
if it has being lying idle for a period. If a connection is to be
reused after being idle for any length of time, ensure that you
explicitly test it before reusing it.
15.13: Why does Connector/J not reconnect to MySQL and re-issue
the statement after a communication failure, instead of throwing
an Exception, even though I use the autoReconnect connection
string option?
There are several reasons for this. The first is transactional
integrity. The MySQL Reference Manual states that "there is no
safe method of reconnecting to the MySQL server without risking
some corruption of the connection state or database state
information". Consider the following series of statements for
example:
conn.createStatement().execute(
"UPDATE checking_account SET balance = balance - 1000.00 WHERE cust
omer='Smith'");
conn.createStatement().execute(
"UPDATE savings_account SET balance = balance + 1000.00 WHERE custo
mer='Smith'");
conn.commit();
Consider the case where the connection to the server fails after
the UPDATE to checking_account. If no exception is thrown, and the
application never learns about the problem, it will continue
executing. However, the server did not commit the first
transaction in this case, so that will get rolled back. But
execution continues with the next transaction, and increases the
savings_account balance by 1000. The application did not receive
an exception, so it continued regardless, eventually committing
the second transaction, as the commit only applies to the changes
made in the new connection. Rather than a transfer taking place, a
deposit was made in this example.
Note that running with autocommit enabled does not solve this
problem. When Connector/J encounters a communication problem,
there is no means to determine whether the server processed the
currently executing statement or not. The following theoretical
states are equally possible:
* The server never received the statement, and therefore no
related processing occurred on the server.
* The server received the statement, executed it in full, but
the response was not received by the client.
If you are running with autocommit enabled, it is not possible to
guarantee the state of data on the server when a communication
exception is encountered. The statement may have reached the
server, or it may not. All you know is that communication failed
at some point, before the client received confirmation (or data)
from the server. This does not only affect autocommit statements
though. If the communication problem occurred during
Connection.commit(), the question arises of whether the
transaction was committed on the server before the communication
failed, or whether the server received the commit request at all.
The second reason for the generation of exceptions is that
transaction-scoped contextual data may be vulnerable, for example:
* Temporary tables.
* User-defined variables.
* Server-side prepared statements.
These items are lost when a connection fails, and if the
connection silently reconnects without generating an exception,
this could be detrimental to the correct execution of your
application.
In summary, communication errors generate conditions that may well
be unsafe for Connector/J to simply ignore by silently
reconnecting. It is necessary for the application to be notified.
It is then for the application developer to decide how to proceed
in the event of connection errors and failures.
15.14: How can I use 3-byte UTF8 with Connector/J?
To use 3-byte UTF8 with Connector/J set characterEncoding=utf8 and
set useUnicode=true in the connection string.
15.15: How can I use 4-byte UTF8, utf8mb4 with Connector/J?
To use 4-byte UTF8 with Connector/J configure the MySQL server
with character_set_server=utf8mb4. Connector/J will then use that
setting as long as characterEncoding has not been set in the
connection string. This is equivalent to autodetection of the
character set.
15.16: Using useServerPrepStmts=false and certain character
encodings can lead to corruption when inserting BLOBs. How can
this be avoided?
When using certain character encodings, such as SJIS, CP932, and
BIG5, it is possible that BLOB data contains characters that can
be interpreted as control characters, for example, backslash, '\'.
This can lead to corrupted data when inserting BLOBs into the
database. There are two things that need to be done to avoid this:
1. Set the connection string option useServerPrepStmts to true.
2. Set SQL_MODE to NO_BACKSLASH_ESCAPES.
Chapter 16. Connector/J Support
16.1. Connector/J Community Support
Oracle provides assistance to the user community by means of its
mailing lists. For Connector/J related issues, you can get help
from experienced users by using the MySQL and Java mailing list.
Archives and subscription information is available online at
http://lists.mysql.com/java.
For information about subscribing to MySQL mailing lists or to
browse list archives, visit http://lists.mysql.com/. See MySQL
Mailing Lists
(http://dev.mysql.com/doc/refman/5.5/en/mailing-lists.html).
Community support from experienced users is also available through
the JDBC Forum (http://forums.mysql.com/list.php?39). You may also
find help from other users in the other MySQL Forums, located at
http://forums.mysql.com. See MySQL Community Support at the MySQL
Forums (http://dev.mysql.com/doc/refman/5.5/en/forums.html).
16.2. How to Report Connector/J Bugs or Problems
The normal place to report bugs is http://bugs.mysql.com/, which
is the address for our bugs database. This database is public, and
can be browsed and searched by anyone. If you log in to the
system, you will also be able to enter new reports.
If you find a sensitive security bug in MySQL Server, please let
us know immediately by sending an email message to
secalert_us@oracle.com. Exception: Support customers should report
all problems, including security bugs, to Oracle Support at
http://support.oracle.com/.
Writing a good bug report takes patience, but doing it right the
first time saves time both for us and for yourself. A good bug
report, containing a full test case for the bug, makes it very
likely that we will fix the bug in the next release.
This section will help you write your report correctly so that you
do not waste your time doing things that may not help us much or
at all.
If you have a repeatable bug report, please report it to the bugs
database at http://bugs.mysql.com/. Any bug that we are able to
repeat has a high chance of being fixed in the next MySQL release.
To report other problems, you can use one of the MySQL mailing
lists.
Remember that it is possible for us to respond to a message
containing too much information, but not to one containing too
little. People often omit facts because they think they know the
cause of a problem and assume that some details do not matter.
A good principle is this: If you are in doubt about stating
something, state it. It is faster and less troublesome to write a
couple more lines in your report than to wait longer for the
answer if we must ask you to provide information that was missing
from the initial report.
The most common errors made in bug reports are (a) not including
the version number of Connector/J or MySQL used, and (b) not fully
describing the platform on which Connector/J is installed
(including the JVM version, and the platform type and version
number that MySQL itself is installed on).
This is highly relevant information, and in 99 cases out of 100,
the bug report is useless without it. Very often we get questions
like, "Why doesn't this work for me?" Then we find that the
feature requested wasn't implemented in that MySQL version, or
that a bug described in a report has already been fixed in newer
MySQL versions.
Sometimes the error is platform-dependent; in such cases, it is
next to impossible for us to fix anything without knowing the
operating system and the version number of the platform.
If at all possible, create a repeatable, standalone testcase that
doesn't involve any third-party classes.
To streamline this process, we ship a base class for testcases
with Connector/J, named 'com.mysql.jdbc.util.BaseBugReport'. To
create a testcase for Connector/J using this class, create your
own class that inherits from com.mysql.jdbc.util.BaseBugReport and
override the methods setUp(), tearDown() and runTest().
In the setUp() method, create code that creates your tables, and
populates them with any data needed to demonstrate the bug.
In the runTest() method, create code that demonstrates the bug
using the tables and data you created in the setUp method.
In the tearDown() method, drop any tables you created in the
setUp() method.
In any of the above three methods, use one of the variants of the
getConnection() method to create a JDBC connection to MySQL:
* getConnection() - Provides a connection to the JDBC URL
specified in getUrl(). If a connection already exists, that
connection is returned, otherwise a new connection is created.
* getNewConnection() - Use this if you need to get a new
connection for your bug report (that is, there is more than
one connection involved).
* getConnection(String url) - Returns a connection using the
given URL.
* getConnection(String url, Properties props) - Returns a
connection using the given URL and properties.
If you need to use a JDBC URL that is different from
'jdbc:mysql:///test', override the method getUrl() as well.
Use the assertTrue(boolean expression) and assertTrue(String
failureMessage, boolean expression) methods to create conditions
that must be met in your testcase demonstrating the behavior you
are expecting (vs. the behavior you are observing, which is why
you are most likely filing a bug report).
Finally, create a main() method that creates a new instance of
your testcase, and calls the run method:
public static void main(String[] args) throws Exception {
new MyBugReport().run();
}
Once you have finished your testcase, and have verified that it
demonstrates the bug you are reporting, upload it with your bug
report to http://bugs.mysql.com/.
Appendix A. Licenses for Third-Party Components
MySQL Connector/J
* Section A.1, "Ant-Contrib License"
* Section A.2, "c3p0 JDBC Library License"
* Section A.3, "GNU Lesser General Public License Version 2.1,
February 1999"
* Section A.4, "jboss-common-jdbc-wrapper.jar License"
* Section A.5, "Simple Logging Facade for Java (SLF4J) License"
A.1. Ant-Contrib License
The following software may be included in this product:
Ant-Contrib
Ant-Contrib
Copyright (c) 2001-2003 Ant-Contrib project. All rights reserved.
Licensed under the Apache 1.1 License Agreement, a copy of which is r
eproduced below.
The Apache Software License, Version 1.1
Copyright (c) 2001-2003 Ant-Contrib project. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
3. The end-user documentation included with the redistribution, if
any, must include the following acknowlegement:
"This product includes software developed by the
Ant-Contrib project (http://sourceforge.net/projects/ant-cont
rib)."
Alternately, this acknowlegement may appear in the software itsel
f,
if and wherever such third-party acknowlegements normally appear.
4. The name Ant-Contrib must not be used to endorse or promote
products derived from this software without prior written
permission. For written permission, please contact
ant-contrib-developers@lists.sourceforge.net.
5. Products derived from this software may not be called "Ant-Contri
b"
nor may "Ant-Contrib" appear in their names without prior written
permission of the Ant-Contrib project.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE ANT-CONTRIB PROJECT OR ITS
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
A.2. c3p0 JDBC Library License
You are receiving a copy of c3p0-0.9.1-pre6.jar in both source and
object code in the following /src/lib/c3p0-0.9.1-pre6.jar. The
terms of the Oracle license do NOT apply to c3p0-0.9.1-pre6.jar;
it is licensed under the following license, separately from the
Oracle programs you receive. If you do not wish to install this
library, you may remove the file /src/lib/c3p0-0.9.1-pre6.jar, but
the Oracle program might not operate properly or at all without
the library.
This component is licensed under Section A.3, "GNU Lesser General
Public License Version 2.1, February 1999."
A.3. GNU Lesser General Public License Version 2.1, February 1999
The following applies to all products licensed under the
GNU Lesser General Public License, Version 2.1: You may
not use the identified files except in compliance with
the GNU Lesser General Public License, Version 2.1 (the
"License"). You may obtain a copy of the License at
http://www.gnu.org/licenses/lgpl-2.1.html. A copy of the
license is also reproduced below. Unless required by
applicable law or agreed to in writing, software distributed
under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
or implied. See the License for the specific language governing
permissions and limitations under the License.
GNU LESSER GENERAL PUBLIC LICENSE
Version 2.1, February 1999
Copyright (C) 1991, 1999 Free Software Foundation, Inc.
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
[This is the first released version of the Lesser GPL. It also count
s
as the successor of the GNU Library Public License, version 2, hence
the version number 2.1.]
Preamble
The licenses for most software are designed to take away your
freedom to share and change it. By contrast, the GNU General Public
Licenses are intended to guarantee your freedom to share and change
free software--to make sure the software is free for all its users.
This license, the Lesser General Public License, applies to some
specially designated software packages--typically libraries--of the
Free Software Foundation and other authors who decide to use it. You
can use it too, but we suggest you first think carefully about whethe
r
this license or the ordinary General Public License is the better
strategy to use in any particular case, based on the explanations bel
ow.
When we speak of free software, we are referring to freedom of use,
not price. Our General Public Licenses are designed to make sure tha
t
you have the freedom to distribute copies of free software (and charg
e
for this service if you wish); that you receive source code or can ge
t
it if you want it; that you can change the software and use pieces of
it in new free programs; and that you are informed that you can do
these things.
To protect your rights, we need to make restrictions that forbid
distributors to deny you these rights or to ask you to surrender thes
e
rights. These restrictions translate to certain responsibilities for
you if you distribute copies of the library or if you modify it.
For example, if you distribute copies of the library, whether grati
s
or for a fee, you must give the recipients all the rights that we gav
e
you. You must make sure that they, too, receive or can get the sourc
e
code. If you link other code with the library, you must provide
complete object files to the recipients, so that they can relink them
with the library after making changes to the library and recompiling
it. And you must show them these terms so they know their rights.
We protect your rights with a two-step method: (1) we copyright the
library, and (2) we offer you this license, which gives you legal
permission to copy, distribute and/or modify the library.
To protect each distributor, we want to make it very clear that
there is no warranty for the free library. Also, if the library is
modified by someone else and passed on, the recipients should know
that what they have is not the original version, so that the original
author's reputation will not be affected by problems that might be
introduced by others.
Finally, software patents pose a constant threat to the existence o
f
any free program. We wish to make sure that a company cannot
effectively restrict the users of a free program by obtaining a
restrictive license from a patent holder. Therefore, we insist that
any patent license obtained for a version of the library must be
consistent with the full freedom of use specified in this license.
Most GNU software, including some libraries, is covered by the
ordinary GNU General Public License. This license, the GNU Lesser
General Public License, applies to certain designated libraries, and
is quite different from the ordinary General Public License. We use
this license for certain libraries in order to permit linking those
libraries into non-free programs.
When a program is linked with a library, whether statically or usin
g
a shared library, the combination of the two is legally speaking a
combined work, a derivative of the original library. The ordinary
General Public License therefore permits such linking only if the
entire combination fits its criteria of freedom. The Lesser General
Public License permits more lax criteria for linking other code with
the library.
We call this license the "Lesser" General Public License because it
does Less to protect the user's freedom than the ordinary General
Public License. It also provides other free software developers Less
of an advantage over competing non-free programs. These disadvantage
s
are the reason we use the ordinary General Public License for many
libraries. However, the Lesser license provides advantages in certai
n
special circumstances.
For example, on rare occasions, there may be a special need to
encourage the widest possible use of a certain library, so that it
becomes a de-facto standard. To achieve this, non-free programs
must be allowed to use the library. A more frequent case is that
a free library does the same job as widely used non-free libraries.
In this case, there is little to gain by limiting the free library
to free software only, so we use the Lesser General Public License.
In other cases, permission to use a particular library in non-free
programs enables a greater number of people to use a large body of
free software. For example, permission to use the GNU C Library in
non-free programs enables many more people to use the whole GNU
operating system, as well as its variant, the GNU/Linux operating
system.
Although the Lesser General Public License is Less protective of th
e
users' freedom, it does ensure that the user of a program that is
linked with the Library has the freedom and the wherewithal to run
that program using a modified version of the Library.
The precise terms and conditions for copying, distribution and
modification follow. Pay close attention to the difference between a
"work based on the library" and a "work that uses the library". The
former contains code derived from the library, whereas the latter mus
t
be combined with the library in order to run.
GNU LESSER GENERAL PUBLIC LICENSE
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0. This License Agreement applies to any software library or other
program which contains a notice placed by the copyright holder or
other authorized party saying it may be distributed under the terms o
f
this Lesser General Public License (also called "this License").
Each licensee is addressed as "you".
A "library" means a collection of software functions and/or data
prepared so as to be conveniently linked with application programs
(which use some of those functions and data) to form executables.
The "Library", below, refers to any such software library or work
which has been distributed under these terms. A "work based on the
Library" means either the Library or any derivative work under
copyright law: that is to say, a work containing the Library or a
portion of it, either verbatim or with modifications and/or translate
d
straightforwardly into another language. (Hereinafter, translation i
s
included without limitation in the term "modification".)
"Source code" for a work means the preferred form of the work for
making modifications to it. For a library, complete source code mean
s
all the source code for all modules it contains, plus any associated
interface definition files, plus the scripts used to control
compilation and installation of the library.
Activities other than copying, distribution and modification are no
t
covered by this License; they are outside its scope. The act of
running a program using the Library is not restricted, and output fro
m
such a program is covered only if its contents constitute a work base
d
on the Library (independent of the use of the Library in a tool for
writing it). Whether that is true depends on what the Library does
and what the program that uses the Library does.
1. You may copy and distribute verbatim copies of the Library's
complete source code as you receive it, in any medium, provided that
you conspicuously and appropriately publish on each copy an
appropriate copyright notice and disclaimer of warranty; keep intact
all the notices that refer to this License and to the absence of any
warranty; and distribute a copy of this License along with the
Library.
You may charge a fee for the physical act of transferring a copy,
and you may at your option offer warranty protection in exchange for
a
fee.
2. You may modify your copy or copies of the Library or any portion
of it, thus forming a work based on the Library, and copy and
distribute such modifications or work under the terms of Section 1
above, provided that you also meet all of these conditions:
a) The modified work must itself be a software library.
b) You must cause the files modified to carry prominent notices
stating that you changed the files and the date of any change.
c) You must cause the whole of the work to be licensed at no
charge to all third parties under the terms of this License.
d) If a facility in the modified Library refers to a function or
a
table of data to be supplied by an application program that uses
the facility, other than as an argument passed when the facility
is invoked, then you must make a good faith effort to ensure that
,
in the event an application does not supply such function or
table, the facility still operates, and performs whatever part of
its purpose remains meaningful.
(For example, a function in a library to compute square roots has
a purpose that is entirely well-defined independent of the
application. Therefore, Subsection 2d requires that any
application-supplied function or table used by this function must
be optional: if the application does not supply it, the square
root function must still compute square roots.)
These requirements apply to the modified work as a whole. If
identifiable sections of that work are not derived from the Library,
and can be reasonably considered independent and separate works in
themselves, then this License, and its terms, do not apply to those
sections when you distribute them as separate works. But when you
distribute the same sections as part of a whole which is a work based
on the Library, the distribution of the whole must be on the terms of
this License, whose permissions for other licensees extend to the
entire whole, and thus to each and every part regardless of who wrote
it.
Thus, it is not the intent of this section to claim rights or contest
your rights to work written entirely by you; rather, the intent is to
exercise the right to control the distribution of derivative or
collective works based on the Library.
In addition, mere aggregation of another work not based on the Librar
y
with the Library (or with a work based on the Library) on a volume of
a storage or distribution medium does not bring the other work under
the scope of this License.
3. You may opt to apply the terms of the ordinary GNU General Publi
c
License instead of this License to a given copy of the Library. To d
o
this, you must alter all the notices that refer to this License, so
that they refer to the ordinary GNU General Public License, version 2
,
instead of to this License. (If a newer version than version 2 of th
e
ordinary GNU General Public License has appeared, then you can specif
y
that version instead if you wish.) Do not make any other change in
these notices.
Once this change is made in a given copy, it is irreversible for
that copy, so the ordinary GNU General Public License applies to all
subsequent copies and derivative works made from that copy.
This option is useful when you wish to copy part of the code of
the Library into a program that is not a library.
4. You may copy and distribute the Library (or a portion or
derivative of it, under Section 2) in object code or executable form
under the terms of Sections 1 and 2 above provided that you accompany
it with the complete corresponding machine-readable source code, whic
h
must be distributed under the terms of Sections 1 and 2 above on a
medium customarily used for software interchange.
If distribution of object code is made by offering access to copy
from a designated place, then offering equivalent access to copy the
source code from the same place satisfies the requirement to
distribute the source code, even though third parties are not
compelled to copy the source along with the object code.
5. A program that contains no derivative of any portion of the
Library, but is designed to work with the Library by being compiled o
r
linked with it, is called a "work that uses the Library". Such a
work, in isolation, is not a derivative work of the Library, and
therefore falls outside the scope of this License.
However, linking a "work that uses the Library" with the Library
creates an executable that is a derivative of the Library (because it
contains portions of the Library), rather than a "work that uses the
library". The executable is therefore covered by this License.
Section 6 states terms for distribution of such executables.
When a "work that uses the Library" uses material from a header fil
e
that is part of the Library, the object code for the work may be a
derivative work of the Library even though the source code is not.
Whether this is true is especially significant if the work can be
linked without the Library, or if the work is itself a library. The
threshold for this to be true is not precisely defined by law.
If such an object file uses only numerical parameters, data
structure layouts and accessors, and small macros and small inline
functions (ten lines or less in length), then the use of the object
file is unrestricted, regardless of whether it is legally a derivativ
e
work. (Executables containing this object code plus portions of the
Library will still fall under Section 6.)
Otherwise, if the work is a derivative of the Library, you may
distribute the object code for the work under the terms of Section 6.
Any executables containing that work also fall under Section 6,
whether or not they are linked directly with the Library itself.
6. As an exception to the Sections above, you may also combine or
link a "work that uses the Library" with the Library to produce a
work containing portions of the Library, and distribute that work
under terms of your choice, provided that the terms permit
modification of the work for the customer's own use and reverse
engineering for debugging such modifications.
You must give prominent notice with each copy of the work that the
Library is used in it and that the Library and its use are covered by
this License. You must supply a copy of this License. If the work
during execution displays copyright notices, you must include the
copyright notice for the Library among them, as well as a reference
directing the user to the copy of this License. Also, you must do on
e
of these things:
a) Accompany the work with the complete corresponding
machine-readable source code for the Library including whatever
changes were used in the work (which must be distributed under
Sections 1 and 2 above); and, if the work is an executable linked
with the Library, with the complete machine-readable "work that
uses the Library", as object code and/or source code, so that the
user can modify the Library and then relink to produce a modified
executable containing the modified Library. (It is understood
that the user who changes the contents of definitions files in th
e
Library will not necessarily be able to recompile the application
to use the modified definitions.)
b) Use a suitable shared library mechanism for linking with the
Library. A suitable mechanism is one that (1) uses at run time a
copy of the library already present on the user's computer system
,
rather than copying library functions into the executable, and (2
)
will operate properly with a modified version of the library, if
the user installs one, as long as the modified version is
interface-compatible with the version that the work was made with
.
c) Accompany the work with a written offer, valid for at
least three years, to give the same user the materials
specified in Subsection 6a, above, for a charge no more
than the cost of performing this distribution.
d) If distribution of the work is made by offering access to copy
from a designated place, offer equivalent access to copy the abov
e
specified materials from the same place.
e) Verify that the user has already received a copy of these
materials or that you have already sent this user a copy.
For an executable, the required form of the "work that uses the
Library" must include any data and utility programs needed for
reproducing the executable from it. However, as a special exception,
the materials to be distributed need not include anything that is
normally distributed (in either source or binary form) with the major
components (compiler, kernel, and so on) of the operating system on
which the executable runs, unless that component itself accompanies
the executable.
It may happen that this requirement contradicts the license
restrictions of other proprietary libraries that do not normally
accompany the operating system. Such a contradiction means you canno
t
use both them and the Library together in an executable that you
distribute.
7. You may place library facilities that are a work based on the
Library side-by-side in a single library together with other library
facilities not covered by this License, and distribute such a combine
d
library, provided that the separate distribution of the work based on
the Library and of the other library facilities is otherwise
permitted, and provided that you do these two things:
a) Accompany the combined library with a copy of the same work
based on the Library, uncombined with any other library
facilities. This must be distributed under the terms of the
Sections above.
b) Give prominent notice with the combined library of the fact
that part of it is a work based on the Library, and explaining
where to find the accompanying uncombined form of the same work.
8. You may not copy, modify, sublicense, link with, or distribute
the Library except as expressly provided under this License. Any
attempt otherwise to copy, modify, sublicense, link with, or
distribute the Library is void, and will automatically terminate your
rights under this License. However, parties who have received copies
,
or rights, from you under this License will not have their licenses
terminated so long as such parties remain in full compliance.
9. You are not required to accept this License, since you have not
signed it. However, nothing else grants you permission to modify or
distribute the Library or its derivative works. These actions are
prohibited by law if you do not accept this License. Therefore, by
modifying or distributing the Library (or any work based on the
Library), you indicate your acceptance of this License to do so, and
all its terms and conditions for copying, distributing or modifying
the Library or works based on it.
10. Each time you redistribute the Library (or any work based on th
e
Library), the recipient automatically receives a license from the
original licensor to copy, distribute, link with or modify the Librar
y
subject to these terms and conditions. You may not impose any furthe
r
restrictions on the recipients' exercise of the rights granted herein
.
You are not responsible for enforcing compliance by third parties wit
h
this License.
11. If, as a consequence of a court judgment or allegation of paten
t
infringement or for any other reason (not limited to patent issues),
conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do no
t
excuse you from the conditions of this License. If you cannot
distribute so as to satisfy simultaneously your obligations under thi
s
License and any other pertinent obligations, then as a consequence yo
u
may not distribute the Library at all. For example, if a patent
license would not permit royalty-free redistribution of the Library b
y
all those who receive copies directly or indirectly through you, then
the only way you could satisfy both it and this License would be to
refrain entirely from distribution of the Library.
If any portion of this section is held invalid or unenforceable under
any particular circumstance, the balance of the section is intended
to apply, and the section as a whole is intended to apply in other
circumstances.
It is not the purpose of this section to induce you to infringe any
patents or other property right claims or to contest validity of any
such claims; this section has the sole purpose of protecting the
integrity of the free software distribution system which is
implemented by public license practices. Many people have made
generous contributions to the wide range of software distributed
through that system in reliance on consistent application of that
system; it is up to the author/donor to decide if he or she is willin
g
to distribute software through any other system and a licensee cannot
impose that choice.
This section is intended to make thoroughly clear what is believed to
be a consequence of the rest of this License.
12. If the distribution and/or use of the Library is restricted in
certain countries either by patents or by copyrighted interfaces, the
original copyright holder who places the Library under this License
may add an explicit geographical distribution limitation excluding
those countries, so that distribution is permitted only in or among
countries not thus excluded. In such case, this License incorporates
the limitation as if written in the body of this License.
13. The Free Software Foundation may publish revised and/or new
versions of the Lesser General Public License from time to time.
Such new versions will be similar in spirit to the present version,
but may differ in detail to address new problems or concerns.
Each version is given a distinguishing version number. If the Librar
y
specifies a version number of this License which applies to it and
"any later version", you have the option of following the terms and
conditions either of that version or of any later version published b
y
the Free Software Foundation. If the Library does not specify a
license version number, you may choose any version ever published by
the Free Software Foundation.
14. If you wish to incorporate parts of the Library into other free
programs whose distribution conditions are incompatible with these,
write to the author to ask for permission. For software which is
copyrighted by the Free Software Foundation, write to the Free
Software Foundation; we sometimes make exceptions for this. Our
decision will be guided by the two goals of preserving the free statu
s
of all derivatives of our free software and of promoting the sharing
and reuse of software generally.
NO WARRANTY
15. BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE, THERE IS NO
WARRANTY FOR THE LIBRARY, TO THE EXTENT PERMITTED BY APPLICABLE LAW.
EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR
OTHER PARTIES PROVIDE THE LIBRARY "AS IS" WITHOUT WARRANTY OF ANY
KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE
LIBRARY IS WITH YOU. SHOULD THE LIBRARY PROVE DEFECTIVE, YOU ASSUME
THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
16. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY
AND/OR REDISTRIBUTE THE LIBRARY AS PERMITTED ABOVE, BE LIABLE TO YOU
FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
LIBRARY (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
FAILURE OF THE LIBRARY TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF
SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUC
H
DAMAGES.
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Libraries
If you develop a new library, and you want it to be of the greatest
possible use to the public, we recommend making it free software that
everyone can redistribute and change. You can do so by permitting
redistribution under these terms (or, alternatively, under the terms
of the ordinary General Public License).
To apply these terms, attach the following notices to the library.
It is safest to attach them to the start of each source file to most
effectively convey the exclusion of warranty; and each file should
have at least the "copyright" line and a pointer to where the full
notice is found.
<one line to give the library's name and a brief idea of what it
does.>
Copyright (C) <year> <name of author>
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version
.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Softwa
re
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
Also add information on how to contact you by electronic and paper ma
il.
You should also get your employer (if you work as a programmer) or yo
ur
school, if any, to sign a "copyright disclaimer" for the library, if
necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the
library `Frob' (a library for tweaking knobs) written by James
Random Hacker.
<signature of Ty Coon>, 1 April 1990
Ty Coon, President of Vice
That's all there is to it!
A.4. jboss-common-jdbc-wrapper.jar License
You are receiving a copy of jboss-common-jdbc-wrapper.jar in both
source and object code in the following
/src/lib/jboss-common-jdbc-wrapper.jar. The terms of the Oracle
license do NOT apply to jboss-common-jdbc-wrapper.jar; it is
licensed under the following license, separately from the Oracle
programs you receive. If you do not wish to install this library,
you may remove the file /src/lib/jboss-common-jdbc-wrapper.jar,
but the Oracle program might not operate properly or at all
without the library.
This component is licensed under Section A.3, "GNU Lesser General
Public License Version 2.1, February 1999."
A.5. Simple Logging Facade for Java (SLF4J) License
The following software may be included in this product:
Simple Logging Facade for Java (SLF4J)
Copyright (c) 2004-2008 QOS.ch
All rights reserved.
Permission is hereby granted, free of charge,
to any person obtaining a copy of this software
and associated documentation files (the "Software"),
to deal in the Software without restriction, including
without limitation the rights to use, copy, modify,
merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom
the Software is furnished to do so, subject to the
following conditions:
The above copyright notice and this permission notice
shall be included in all copies or substantial portions
of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY
OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO
EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
OR OTHER DEALINGS IN THE SOFTWARE.
Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights
reserved. Legal Notices