23.3. MySQL Connector/J

MySQL provides connectivity for client applications developed in the Java programming language via a JDBC driver, which is called MySQL Connector/J.

MySQL Connector/J is a JDBC-3.0 “Type 4” driver, which means that is pure Java, implements version 3.0 of the JDBC specification, and communicates directly with the MySQL server using the MySQL protocol.

This document is arranged for a beginning JDBC developer. If you are already experienced with using JDBC, you might consider starting with the Section 23.3.2, “Installing Connector/J”.

Although JDBC is useful by itself, we would hope that if you are not familiar with JDBC that after reading the first few sections of this manual, that you would avoid using “naked” JDBC for all but the most trivial problems and consider using one of the popular persistence frameworks such as Hibernate, Spring's JDBC templates or Ibatis SQL Maps to do the majority of repetitive work and heavier lifting that is sometimes required with JDBC.

This section is not designed to be a complete JDBC tutorial. If you need more information about using JDBC you might be interested in the following online tutorials that are more in-depth than the information presented here:

JDBC Basics — A tutorial from Sun covering beginner topics in JDBC
JDBC Short Course — A more in-depth tutorial from Sun and JGuru

23.3.1. Basic JDBC concepts

This section provides some general JDBC background.

23.3.1.1. Connecting to MySQL Using the `DriverManager` Interface

When you are using JDBC outside of an application server, the DriverManager class manages the establishment of Connections.

The DriverManager needs to be told which JDBC drivers it should 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:

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 23.1. Obtaining a Connection From the DriverManager

This example shows how you can obtain a Connection instance from the DriverManager. There are a few different signatures for the getConnection() method. You should see 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;

    ... try {
            Connection 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.

23.3.1.2. Using Statements 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 via one of the DriverManager.getConnection() or DataSource.getConnection() methods described earlier.

Once you have a Statement instance, you can execute a SELECT 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 affected by the update statement.

If you don't know ahead of time whether the SQL statement will be a SELECT or an UPDATE/INSERT, then you can use the execute(String SQL) method. This method will return true if the SQL query was a SELECT, or false if it was an UPDATE, INSERT, or DELETE statement. If the statement was a SELECT query, you can retrieve the results by calling the getResultSet() method. If the statement was an UPDATE, INSERT, or DELETE statement, you can retrieve the affected rows count by calling getUpdateCount() on the Statement instance.

Example 23.2. Using java.sql.Statement to Execute a SELECT Query

// assume that conn is an already created JDBC connection
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 ....
} 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;
    }
}

23.3.1.3. Using `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.

MySQL's stored procedure syntax is documented in the "Stored Procedures and Functions" section of the MySQL Reference Manual.

Connector/J exposes stored procedure functionality through JDBC's CallableStatement interface.

The following example shows a stored procedure that returns the value of inOutParam incremented by 1, and the string passed in via inputParam as a ResultSet:

Example 23.3. Stored Procedure Example

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:

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 23.4. 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, you should try to minimize unnecessary calls to Connection.prepareCall() by reusing CallableStatement instances in your code.

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 23.5. 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);
...

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 23.6. 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);

...

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 23.7. 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

...

23.3.1.4. Retrieving `AUTO_INCREMENT` Column Values

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 to a table that had an AUTO_INCREMENT key. Using the MySQL-specific method call isn't portable, and issuing a SELECT 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 23.8. 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 23.9. 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 23.10. 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
        }
    }
}

When you run the preceding example code, you should get the following output: Key returned from getGeneratedKeys(): 1 Key returned from SELECT LAST_INSERT_ID(): 1 Key returned for inserted row: 2 You should be aware, that 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 will be 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.

23.3.2. Installing Connector/J

Use the following instructions to install Connector/J

23.3.2.1. Required Software Versions

23.3.2.1.1. Java Versions Supported

MySQL Connector/J supports Java-2 JVMs, including JDK-1.2.x, JDK-1.3.x, JDK-1.4.x and JDK-1.5.x, and requires JDK-1.4.x or newer to compile (but not run). MySQL Connector/J does not support JDK-1.1.x or JDK-1.0.x

Because of the implementation of java.sql.Savepoint, Connector/J 3.1.0 and newer will not run on JDKs older than 1.4 unless the class verifier is turned off (-Xverify:none), as 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.

23.3.2.1.2. MySQL Server Version Guidelines

MySQL Connector/J supports all known MySQL server versions. Some features (foreign keys, updatable result sets) require more recent versions of MySQL to operate.

When connecting to MySQL server version 4.1 or newer, it is best to use MySQL Connector/J version 3.1, as it has full support for features in the newer versions of the server, including Unicode characters, views, stored procedures and server-side prepared statements.

Although Connector/J version 3.0 will connect to MySQL server, version 4.1 or newer, and implements Unicode characters and the new authorization mechanism, Connector/J 3.0 will not be updated to support new features in current and future server versions.

23.3.2.1.3. 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 a class-file only “binary” .jar archive named "mysql-connector-java-[version]-bin.jar", and starting with Connector/J 3.1.8 a “debug” build of the driver in a file named "mysql-connector-java-[version]-bin-g.jar".

Starting with Connector/J 3.1.9, we don't ship the .class files “unbundled,” they are only available in the JAR archives that ship with the driver.

You should not use the “debug” build of the driver unless instructed to do so when reporting a problem or bug to MySQL AB, 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.

You will need to use the appropriate graphical or command-line utility to un-archive the distribution (for example, WinZip for the .zip archive, and tar for the .tar.gz archive). Because there are potentially long filenames in the distribution, we use the GNU tar archive format. You will need to use GNU tar (or an application that understands the GNU tar archive format) to unpack the .tar.gz variant of the distribution.

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 your JVM

If you are going to use the driver with the JDBC DriverManager, you would use "com.mysql.jdbc.Driver" as the class that implements java.sql.Driver.

Example 23.11. Setting the CLASSPATH Under UNIX

The following command works for 'csh' under UNIX:

$ setenv CLASSPATH /path/to/mysql-connector-java-[version]-bin.jar:$CLASSPATH

The above command can be added to the appropriate startup file for the login shell to make MySQL Connector/J available to all Java applications.

If you want to use MySQL Connector/J with an application server such as Tomcat or JBoss, you will have to 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 Section 23.3.4, “Using Connector/J with J2EE and Other Java Frameworks”. 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 via 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

23.3.2.2. Upgrading from an Older Version

MySQL AB tries to keep the upgrade process as easy as possible, however as is the case with any software, sometimes changes need to be made in new versions to support new features, improve existing functionality, or comply with new standards.

This section has information about what users who are upgrading from one version of Connector/J to another (or to a new version of the MySQL server, with respect to JDBC functionality) should be aware of.

23.3.2.2.1. 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 via configuration properties.

Unicode Character Sets — See the next section, as well as Chapter 10, Character Set Support, for information on this new feature of MySQL. 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 via 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 following connection property:
useServerPrepStmts=false
Datetimes with all-zero components ('0000-00-00 ...') — These values can not 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 allowable values are: 'exception' (the default), which throws an SQLException with an SQLState of 'S1009', 'convertToNull', which returns NULL instead of the date, and '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 via ' noDatetimeStringSync=true ' (the default value is 'false') so that you can get retrieve the unaltered all-zero value as a String. It should be noted 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 following configuration property:
useSqlStateCodes=false
Calling ResultSet.getString() on a BLOB column will now return the address of the byte[] array that represents it, instead of a String representation of the BLOB. BLOBs have no character set, so they can't be converted to java.lang.Strings without data loss or corruption.
To store strings in MySQL with LOB behavior, use one of the TEXT types, which the driver will treat as a java.sql.Clob.
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 don't ship the .class files “unbundled,” they are only available in the JAR archives that ship with the driver.
You should not use the “debug” build of the driver unless instructed to do so when reporting a problem or bug to MySQL AB, 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.

23.3.2.2.2. 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, you should 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

23.3.2.3. Installing from the Development Source Tree

Caution

You should read this section only if you are interested in helping us test our new code. If you just want to get MySQL Connector/J up and running on your system, you should use a standard release distribution.

To install MySQL Connector/J from the development source tree, make sure that you have the following prerequisites:

Subversion, to check out the sources from our repository (available from http://subversion.tigris.org/).
Apache Ant version 1.6 or newer (available from http://ant.apache.org/).
JDK-1.4.2 or later. Although MySQL Connector/J can be installed on older JDKs, to compile it from source you must have at least JDK-1.4.2.

The Subversion source code repository for MySQL Connector/J is located at http://svn.mysql.com/svnpublic/connector-j. In general, you should not check out the entire repository because it contains every branch and tag for MySQL Connector/J and is quite large.

To check out and compile a specific branch of MySQL Connector/J, follow these steps:

At the time of this writing, there are three active branches of Connector/J: branch_3_0, branch_3_1 and branch_5_0. Check out the latest code from the branch that you want with the following command (replacing [major] and [minor] with appropriate version numbers):
```
shell> svn co http://svn.mysql.com/svnpublic/connector-j/branches/branch_[major]_[minor]/connector-j
```
This creates a connector-j subdirectory in the current directory that contains the latest sources for the requested branch.
Change location to the connector-j directory to make it your current working directory:
```
shell> cd connector-j
```
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
```
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 23.3.2.1.3, “Installing the Driver and Configuring the CLASSPATH”.

23.3.3. JDBC Reference

23.3.3.1. 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 to remain backward-compatible with MM.MySQL. You should use this class name when registering the driver, or when otherwise configuring software to use MySQL Connector/J.

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 hostname 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]...

If the database is not specified, the connection will be made with no default database. In this case, you will need to either call the setCatalog() method on the Connection instance or fully-specify table names using the database name (i.e. 'SELECT dbname.tablename.colname FROM dbname.tablename...') in your SQL. Not specifying the database to use upon connection is generally only useful when building tools that work with multiple databases, such as GUI database managers.

MySQL Connector/J has fail-over support. This allows the driver to fail-over to any number of “slave” hosts and still perform read-only queries. Fail-over only happens when the connection is in an autoCommit(true) state, because fail-over can not happen reliably when a transaction is in progress. Most application servers and connection pools set autoCommit to 'true' at the end of every transaction/connection use.

The fail-over 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 (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 will be set to read-only state, so queries that would modify data will have exceptions thrown (the query will never be processed by the MySQL server).

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.MysqlConnectionPoolDataSource
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 javax.sql.DataSource's setURL() method.
Note
If the mechanism you use to configure a JDBC URL is XML-based, you will need to 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
password	The password to use when connecting		all
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
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
interactiveClient	Set the CLIENT_INTERACTIVE flag, which tells MySQL to timeout connections based on INTERACTIVE_TIMEOUT instead of WAIT_TIMEOUT	false	3.1.0
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

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'thandle SQLExceptions properly, and is only designed to be used when you are unable to configure your application to handle SQLExceptions resulting from dead andstale connections properly. Alternatively, investigate setting the MySQL server variable "wait_timeout"to some 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
reconnectAtTxEnd	If autoReconnect is set to true, should the driver attempt reconnectionsat the end of every transaction?	false	3.0.10
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 to reconnect to the master server? Whichever condition is met first, 'queriesBeforeRetryMaster' or 'secondsBeforeRetryMaster' will cause an attempt to be made to reconnect to the master. Time in seconds, defaults to 30	30	3.0.2
enableDeprecatedAutoreconnect	Auto-reconnect functionality is deprecated starting with version 3.2, and will be removed in version 3.3. Set this property to 'true' to disable the check for the feature being configured.	false	3.2.1
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'	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
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

Performance Extensions.

Property Name	Definition	Default Value	Since Version
metadataCacheSize	The number of queries to cacheResultSetMetadata for if cacheResultSetMetaData is set to 'true' (default 50)	50	3.1.1
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
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
holdResultsOpenOverStatementClose	Should the driver close result sets on Statement.close() as required by the JDBC specification?	false	3.1.7
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 optimium number of parameters per batch and you might receive anan 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
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? (The default of "true" for this is appropriate for newer JVMs	true	5.0.1
useLocalSessionState	Should the driver refer to the internal values of autocommit and transaction isolation that are set by Connection.setAutoCommit() and Connection.setTransactionIsolation(), rather than querying the database?	false	3.1.7
useReadAheadInput	Use newer, optimized non-blocking, buffered input stream when reading from the server?	true	3.1.5

Debuging/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
profileSQL	Trace queries and their execution/fetch times to the configured logger (true/false) defaults to 'false'	false	3.1.0
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
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
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
logSlowQueries	Should queries that take longer than 'slowQueryThresholdMillis' be logged?	false	3.1.2
traceProtocol	Should trace-level network protocol be logged?	false	3.1.2

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
connectionCollation	If set, tells the server to use this collation via 'set collation_connection'		3.0.13
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
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
capitalizeTypeNames	Capitalize type names in DatabaseMetaData? (usually only useful when using WebObjects, true/false, defaults to 'false')	false	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
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	N/A	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
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)?	true	3.1.2
maxRows	The maximum number of rows to return (0, the default means return all rows).	-1	all versions
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 INOUT VARCHARs) 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
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
processEscapeCodesForPrepStmts	Should the driver process escape codes in queries that are prepared?	true	3.1.12
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
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
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
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
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
useServerPrepStmts	Use server-side prepared statements if the server supports them? (defaults to 'true').	true	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 zeroes (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 via named pipes on Windows NT/2000/XP using the 'NamedPipeSocketFactory' as a plugin-socket factory via the 'socketFactory' property. If you don't use a 'namedPipePath' property, the default of '\\.\pipe\MySQL' will be used. If you use the NamedPipeSocketFactory, the hostname and port number values in the JDBC url will be ignored.

Adding the following property to your URL will enable the NamedPipeSocketFactory:

socketFactory=com.mysql.jdbc.NamedPipeSocketFactory

Named pipes only work when connecting to a MySQL server on the same physical machine as the one the JDBC driver is being used on. In simple performance tests, it appears that named pipe access is between 30%-50% faster than the standard TCP/IP access.

You can create your own socket factories by following the example code in com.mysql.jdbc.NamedPipeSocketFactory, or com.mysql.jdbc.StandardSocketFactory.

23.3.3.2. JDBC API Implementation Notes

MySQL Connector/J passes all of the tests in the publicly-available version of Sun's JDBC compliance test suite. However, in many places the JDBC specification is vague about how certain functionality should be implemented, or the specification allows leeway in implementation.

This section gives details on a interface-by-interface level about how certain implementation decisions may affect how you use MySQL Connector/J.

Blob
The Blob implementation does not allow in-place modification (they are 'copies', as reported by the DatabaseMetaData.locatorsUpdateCopies() method). Because of this, you should use the corresponding PreparedStatement.setBlob() or ResultSet.updateBlob() (in the case of updatable result sets) methods to save changes back to the database.
Starting with Connector/J version 3.1.0, you can emulate Blobs with locators by adding the property 'emulateLocators=true' to your JDBC URL. You must then use a column alias with the value of the column set to the actual name of the Blob column in the SELECT that you write to retrieve the Blob. The SELECT must also reference only one table, the table must have a primary key, and the SELECT must cover all columns that make up the primary key. The driver will then delay loading the actual Blob data until you retrieve the Blob and call retrieval methods (getInputStream(), getBytes(), and so forth) on it.
CallableStatement
Starting with Connector/J 3.1.1, stored procedures are supported when connecting to MySQL version 5.0 or newer via 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, you should use the PreparedStatement.setClob() method to save changes back to the database. The JDBC API does not have a ResultSet.updateClob() method.
Connection
Unlike older versions of MM.MySQL the isClosed() method does not “ping” the server to determine if it is alive. 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, you should issue a simple query, such as "SELECT 1". The driver will throw an exception if the connection is no longer valid.
DatabaseMetaData
Foreign Key information (getImported/ExportedKeys() and getCrossReference()) is only available from 'InnoDB'-type tables. However, the driver uses 'SHOW CREATE TABLE' to retrieve this information, so when other storage engines support foreign keys, the driver will transparently support them as well.
Driver
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 via setBinaryStream(), setAsciiStream(), setUnicodeStream(), setBlob(), or setClob(). If you want to re-execute the statement with any “large” parameter changed to a non-“large” parameter, it is necessary to call clearParameters() and set all parameters again. The reason for this is as follows:
- The driver streams the 'large' data 'out-of-band' to the prepared statement on the server side when the parameter is set (before execution of the prepared statement).
- Once that has been done, the stream used to read the data on the client side is closed (as per the JDBC spec), and can't be read from again.
- If a parameter changes from “large” to non-“large,” 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, via the setBinaryStream(), setAsciiStream(), setUnicodeStream(), setBlob() or setClob() methods.
Consequently, if you want to change the “type” of a parameter to a non-“large” 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 can not 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, you need to 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 will have to 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, you should 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.
MySQL does not support SQL cursors, and the JDBC driver doesn't emulate them, so "setCursorName()" has no effect.

23.3.3.3. 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 numerical type can be converted to any of the Java numerical types, although round-off, overflow, or loss of precision may occur.

Starting with Connector/J 3.1.0, the JDBC driver will issue warnings or throw 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:

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 following type conversions between MySQL and Java types, following the JDBC specification where appropriate:

MySQL Types to Java Types for ResultSet.getObject().

MySQL Type Name	Returned as Java Class
BIT(1) (new in MySQL-5.0)	`java.lang.Boolean`
BIT( > 1) (new in MySQL-5.0)	`byte[]`
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	See TINYINT, above as these are aliases for TINYINT(1), currently.
SMALLINT[(M)] [UNSIGNED]	`java.lang.Integer` (regardless if UNSIGNED or not)
MEDIUMINT[(M)] [UNSIGNED]	`java.lang.Integer,` if UNSIGNED `java.lang.Long`
INT,INTEGER[(M)] [UNSIGNED]	`java.lang.Integer`, if UNSIGNED `java.lang.Long`
BIGINT[(M)] [UNSIGNED]	`java.lang.Long`, if UNSIGNED `java.math.BigInteger`
FLOAT[(M,D)]	`java.lang.Float`
DOUBLE[(M,B)]	`java.lang.Double`
DECIMAL[(M[,D])]	`java.math.BigDecimal`
DATE	`java.sql.Date`
DATETIME	`java.sql.Timestamp`
TIMESTAMP[(M)]	`java.sql.Timestamp`
TIME	`java.sql.Time`
YEAR[(2\|4)]	`java.sql.Date` (with the date set two January 1st, at midnight)
CHAR(M)	`java.lang.String` (unless the character set for the column is BINARY, then `byte[]` is returned.
VARCHAR(M) [BINARY]	`java.lang.String` (unless the character set for the column is BINARY, then `byte[]` is returned.
BINARY(M)	`byte[]`
VARBINARY(M)	`byte[]`
TINYBLOB	`byte[]`
TINYTEXT	`java.lang.String`
BLOB	`byte[]`
TEXT	`java.lang.String`
MEDIUMBLOB	`byte[]`
MEDIUMTEXT	`java.lang.String`
LONGBLOB	`byte[]`
LONGTEXT	`java.lang.String`
ENUM('value1','value2',...)	`java.lang.String`
SET('value1','value2',...)	`java.lang.String`

23.3.3.4. 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 via 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() .

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.

Starting with MySQL Server 4.1, 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.

The character encoding between client and server is automatically detected upon connection. The encoding used by the driver is specified on the server via the character_set system variable for server versions older than 4.1.0 and character_set_server for server versions 4.1.0 and newer. For more information, see Section 10.3.1, “Server Character Set and Collation”.

To override the automatically-detected encoding on the client side, use the characterEncoding property in the URL used to connect to the server.

When specifying character encodings on the client side, Java-style names should be used. The following table lists Java-style names for MySQL character sets:

MySQL to Java Encoding Name Translations.

MySQL Character Set Name	Java-Style Character Encoding Name
usa7	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
euc_kr	EUC_KR
latin1	ISO8859_1
latin1_de	ISO8859_1
german1	ISO8859_1
danish	ISO8859_1
latin2	ISO8859_2
czech	ISO8859_2
hungarian	ISO8859_2
croat	ISO8859_2
greek	ISO8859_7
hebrew	ISO8859_8
latin5	ISO8859_9
latvian	ISO8859_13
latvian1	ISO8859_13
estonia	ISO8859_13
dos	Cp437
pclatin2	Cp852
cp866	Cp866
koi8_ru	KOI8_R
tis620	TIS620
win1250	Cp1250
win1250ch	Cp1250
win1251	Cp1251
cp1251	Cp1251
win1251ukr	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.

To allow multiple character sets to be sent from the client, the "UTF-8" encoding should be used, either by configuring "utf8" as the default server character set, or by configuring the JDBC driver to use "UTF-8" through the characterEncoding property.

23.3.3.5. 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, see: http://www.mysql.com/doc/en/secure-connections.html
A client certificate (covered later in this section)

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.

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. It's located in the 'bin' subdirectory of your JDK or JRE):

shell> keytool -import -alias mysqlServerCACert -file cacert.pem -keystore truststore

Keytool will respond with the following information:

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=Som
e-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 will then need to generate a client certificate, so that the MySQL server knows that it is talking to a secure client:

 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.

You should 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.

-Djavax.net.ssl.keyStore=path_to_keystore_file
-Djavax.net.ssl.keyStorePassword=*********
-Djavax.net.ssl.trustStore=path_to_truststore_file
-Djavax.net.ssl.trustStorePassword=*********

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.

23.3.3.6. Using Master/Slave Replication with ReplicationConnection

Starting with Connector/J 3.1.7, we've made available 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, simple 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://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 one
        // from the list
        //

        conn.setReadOnly(true);

        ResultSet rs = conn.createStatement().executeQuery("SELECT a,b,c FROM some_other_table");

         .......
    }
}

23.3.4. Using Connector/J with J2EE and Other Java Frameworks

This section describes how to use Connector/J in several contexts.

23.3.4.1. General J2EE Concepts

This section provides general background on J2EE concepts that pertain to use of Connector/J.

23.3.4.1.1. Understanding Connection Pooling

Connection pooling is a technique of creating and managing a pool of connections that are ready for use by any thread that needs them.

This technique of “pooling” connections is based on the fact that most applications only need a thread to have access to a JDBC connection when they are actively processing a transaction, which usually take only milliseconds to complete. When not processing a transaction, the connection would otherwise sit idle. Instead, connection pooling allows 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 may be used by any other threads that want to use it.

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, however with connection pooling, your thread may end up using either a new, or already-existing connection.

Connection pooling can greatly increase the performance of your Java application, while reducing overall resource usage. 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 straight-forward JDBC programming techniques.
Controlled resource usage
If you don't use connection pooling, and instead create a new connection every time a thread needs one, your application's resource usage can be quite wasteful and lead to unpredictable behavior under load.

Remember that 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.

Luckily, 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 fine with MySQL Connector/J.

Generally, you configure a connection pool in your application server configuration files, and access it via 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 23.12. 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 instances
          * 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 allows 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;
            }
        }
    }
}

As shown in the example above, after obtaining the JNDI InitialContext, and looking up the DataSource, the rest of the code should look familiar to anyone who has done JDBC programming in the past.

The most important thing to remember when using connection pooling is to make sure that no matter what happens in your code (exceptions, flow-of-control, and so forth), connections, and anything created by them (such as statements or result sets) are closed, so that they may be re-used, otherwise they will be “stranded,” which in the best case means that the MySQL server resources they represent (such as buffers, locks, or sockets) may be tied up for some time, or worst case, may be tied up forever.

What's the Best Size for my Connection Pool?

As with all other configuration rules-of-thumb, the answer is “It depends.” Although the optimal size depends on anticipated load and average database transaction time, the optimum connection pool size is 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 response times that are acceptable.

To correctly size a connection pool for your application, you should 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.

23.3.4.2. Using Connector/J with Tomcat

The following instructions are based on the instructions for Tomcat-5.x, available at http://jakarta.apache.org/tomcat/tomcat-5.0-doc/jndi-datasource-examples-howto.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"/>

  <!-- The name you used above, must match _exactly_ here!

       The connection pool will be bound into JNDI with the name
       "java:/comp/env/jdbc/MySQLDB"
  -->

  <ResourceParams name="jdbc/MySQLDB">
    <parameter>
      <name>factory</name>
      <value>org.apache.commons.dbcp.BasicDataSourceFactory</value>
    </parameter>

    <!-- Don't set this any higher than max_connections on your
         MySQL server, usually this should be a 10 or a few 10's
         of connections, not hundreds or thousands -->

    <parameter>
      <name>maxActive</name>
      <value>10</value>
    </parameter>

    <!-- You don't want to many idle connections hanging around
         if you can avoid it, only enough to soak up a spike in
         the load -->

    <parameter>
      <name>maxIdle</name>
      <value>5</value>
    </parameter>

    <!-- Don't use autoReconnect=true, it's going away eventually
         and it's a crutch for older connection pools that couldn't
         test connections. You need to decide whether your application is
         supposed to deal with SQLExceptions (hint, it should), and
         how much of a performance penalty you're willing to pay
         to ensure 'freshness' of the connection -->

    <parameter>
      <name>validationQuery</name>
      <value>SELECT 1</value>
    </parameter>

   <!-- The most conservative approach is to test connections
        before they're given to your application. For most applications
        this is okay, the query used above is very small and takes
        no real server resources to process, other than the time used
        to traverse the network.

        If you have a high-load application you'll need to rely on
        something else. -->

    <parameter>
      <name>testOnBorrow</name>
      <value>true</value>
    </parameter>

   <!-- Otherwise, or in addition to testOnBorrow, you can test
        while connections are sitting idle -->

    <parameter>
      <name>testWhileIdle</name>
      <value>true</value>
    </parameter>

    <!-- You have to set this value, otherwise even though
         you've asked connections to be tested while idle,
         the idle evicter thread will never run -->

    <parameter>
      <name>timeBetweenEvictionRunsMillis</name>
      <value>10000</value>
    </parameter>

    <!-- Don't allow connections to hang out idle too long,
         never longer than what wait_timeout is set to on the
         server...A few minutes or even fraction of a minute
         is sometimes okay here, it depends on your application
         and how much spikey load it will see -->

    <parameter>
      <name>minEvictableIdleTimeMillis</name>
      <value>60000</value>
    </parameter>

    <!-- Username and password used when connecting to MySQL -->

    <parameter>
     <name>username</name>
     <value>someuser</value>
    </parameter>

    <parameter>
     <name>password</name>
     <value>somepass</value>
    </parameter>

    <!-- Class name for the Connector/J driver -->

    <parameter>
       <name>driverClassName</name>
       <value>com.mysql.jdbc.Driver</value>
    </parameter>

    <!-- The JDBC connection url for connecting to MySQL, notice
         that if you want to pass any other MySQL-specific parameters
         you should pass them here in the URL, setting them using the
         parameter tags above will have no effect, you will also
         need to use &amp; to separate parameter values as the
         ampersand is a reserved character in XML -->

    <parameter>
      <name>url</name>
      <value>jdbc:mysql://localhost:3306/test</value>
    </parameter>

  </ResourceParams>
</Context>

In general, you should 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 unfortunately 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 ' SQL
state: null

23.3.4.3. 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>
        <!-- This connection pool will be bound into JNDI with the name
             "java:/MySQLDB" -->

        <jndi-name>MySQLDB</jndi-name>
        <connection-url>jdbc:mysql://localhost:3306/dbname</connection-url>
        <driver-class>com.mysql.jdbc.Driver</driver-class>
        <user-name>user</user-name>
        <password>pass</password>

        <min-pool-size>5</min-pool-size>

        <!-- Don't set this any higher than max_connections on your
         MySQL server, usually this should be a 10 or a few 10's
         of connections, not hundreds or thousands -->

        <max-pool-size>20</max-pool-size>

        <!-- Don't allow connections to hang out idle too long,
         never longer than what wait_timeout is set to on the
         server...A few minutes is usually okay here,
         it depends on your application
         and how much spikey load it will see -->

        <idle-timeout-minutes>5</idle-timeout-minutes>

        <!-- If you're using Connector/J 3.1.8 or newer, you can use
             our implementation of these to increase the robustness
             of the connection pool. -->

        <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>

23.3.5. Diagnosing Connector/J Problems

This section describes how to solve problems that you may encounter when using Connector/J.

23.3.5.1. Common Problems and Solutions

There are a few issues that seem to be commonly encountered often by users of MySQL Connector/J. This section deals with their symptoms, and their resolutions.

24.3.5.1.1:

Question:

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

What's going on? I can connect just fine with the MySQL command-line client.

Answer:

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 should be allowed.

You must add grants to allow this to happen. The following is an example of how to do this (but not the most secure).

From the mysql command-line client, logged in as a user that can grant privileges, issue the following command:

GRANT ALL PRIVILEGES ON [dbname].* to
                '[user]'@'[hostname]' identified by
                '[password]'

replacing [dbname] with the name of your database, [user] with the user name, [hostname] with the host that MySQL Connector/J will be connecting from, and [password] with the password you want to use. Be aware that RedHat Linux is broken with respect to the hostname portion for the case when you are connecting from localhost. You need to use "localhost.localdomain" for the [hostname] value in this case. Follow this by issuing the "FLUSH PRIVILEGES" command.

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 hostname localhost. If you are testing connectivity to localhost, use 127.0.0.1 as the hostname instead.

Warning

If you don't understand what the 'GRANT' command does, or how it works, you should read and understand the 'General Security Issues and the MySQL Access Privilege System' section of the MySQL manual before attempting to change privileges.

Changing privileges and permissions improperly in MySQL can potentially cause your server installation to not have optimal security properties.

24.3.5.1.2:

Question:

My application throws an SQLException 'No Suitable Driver'. Why is this happening?

Answer:

One of two things are happening. Either the driver is not in your CLASSPATH or your URL format is incorrect (see the Section 23.3.2, “Installing Connector/J” section.).

24.3.5.1.3:

Question:

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

Answer:

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 MySQL AB 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).

24.3.5.1.4:

Question:

I have a servlet/application that works fine for a day, and then stops working overnight

Answer:

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 23.3.3.1, “Driver/Datasource Class Names, URL Syntax and Configuration Properties for Connector/J”).

Also, you should be catching SQLExceptions in your application and dealing 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 APIDOCS) to "08S01" when it encounters network-connectivity issues during the processing of a query. Your application code should then attempt to re-connect to MySQL at this point.

The following (simplistic) example shows what code that can handle these exceptions might look like:

Example 23.13. 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 transacational 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 going
                // 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--;
                } 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));
    }

24.3.5.1.5:

Question:

I'm trying to use JDBC-2.0 updatable result sets, and I get an exception saying my result set is not updatable.

Answer:

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, the query must select every primary key and the query can only span one table (that is, no joins). This is outlined in the JDBC specification.

23.3.5.2. 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 have found a sensitive security bug in MySQL, you can send email to security_at_@mysql.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 don't 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 don't 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, you should create a repeatable, stanalone 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, you should 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 (i.e. there's 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/.

23.3.6. MySQL Connector/J Change History

23.3.6.1. Changes in MySQL Connector/J 5.0.3 (26 July 2006)

Fixed Statement.cancel() causes NullPointerException if underlying connection has been closed due to server failure. (Bug #20650)
Added configuration option "noAccessToProcedureBodies" which will cause the driver to create basic parameter metadata for CallableStatements when the user does not have access to procedure bodies via "SHOW CREATE PROCEDURE" or selecting from mysql.proc instead of throwing an exception. The default value for this option is "false"

23.3.6.2. Changes in MySQL Connector/J 5.0.2-beta (11 July 2006)

Fixed can't use XAConnection for local transactions when no global transaction is in progress. (Bug #17401)
Fixed driver fails on non-ASCII platforms. The driver was assuming that the platform character set would be a superset of MySQL's latin1 when doing the handshake for authentication, and when reading error messages. We now use Cp1252 for all strings sent to the server during the handshake phase, and a hard-coded mapping of the language systtem variable to the character set that is used for error messages. (Bug #18086)
Fixed ConnectionProperties (and thus some subclasses) are not serializable, even though some J2EE containers expect them to be. (Bug #19169)
Fixed MysqlValidConnectionChecker for JBoss doesn't work with MySQLXADataSources. (Bug #20242)
Better caching of character set converters (per-connection) to remove a bottleneck for multibyte character sets.
Added connection/datasource property pinGlobalTxToPhysicalConnection (defaults to false). When set to true, when using XAConnections, the driver ensures 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, and is also a workaround for transaction managers that don't maintain thread affinity for a global transaction (most either always maintain thread affinity, or have it as a configuration option).
MysqlXaConnection.recover(int flags) now allows combinations of XAResource.TMSTARTRSCAN and TMENDRSCAN. To simulate the “scanning” nature of the interface, we return all prepared XIDs for TMSTARTRSCAN, and no new XIDs for calls with TMNOFLAGS, or TMENDRSCAN when not in combination with TMSTARTRSCAN. This change was made for API compliance, as well as integration with IBM WebSphere's transaction manager.

23.3.6.3. Changes in MySQL Connector/J 5.0.1-beta (Not Released)

Not released due to a packaging error

23.3.6.4. Changes in MySQL Connector/J 5.0.0-beta (22 December 2005)

XADataSource implemented (ported from 3.2 branch which won't be released as a product). Use com.mysql.jdbc.jdbc2.optional.MysqlXADataSource as your datasource class name in your application server to utilize XA transactions in MySQL-5.0.10 and newer.
PreparedStatement.setString() didn't work correctly when sql_mode on server contained NO_BACKSLASH_ESCAPES and no characters that needed escaping were present in the string.
Attempt detection of the MySQL type BINARY (it's an alias, so this isn't always reliable), and use the java.sql.Types.BINARY type mapping for it.
Moved -bin-g.jar file into separate debug subdirectory to avoid confusion.
Don't allow .setAutoCommit(true), or .commit() or .rollback() on an XA-managed connection as per the JDBC specification.
If the connection useTimezone is set to true, then also respect time zone conversions in escape-processed string literals (for example, "{ts ...}" and "{t ...}").
Return original column name for RSMD.getColumnName() if the column was aliased, alias name for .getColumnLabel() (if aliased), and original table name for .getTableName(). Note this only works for MySQL-4.1 and newer, as older servers don't make this information available to clients.
Setting useJDBCCompliantTimezoneShift=true (it's not the default) causes the driver to use GMT for all TIMESTAMP/DATETIME time zones, and the current VM time zone for any other type that refers to time zones. This feature can not be used when useTimezone=true to convert between server and client time zones.
Add one level of indirection of internal representation of CallableStatement parameter metadata to avoid class not found issues on JDK-1.3 for ParameterMetadata interface (which doesn't exist prior to JDBC-3.0).
Added unit tests for XADatasource, as well as friendlier exceptions for XA failures compared to the "stock" XAException (which has no messages).
Idle timeouts cause XAConnections to whine about rolling themselves back. (Bug #14729)
Added support for Connector/MXJ integration via url subprotocol jdbc:mysql:mxj://....
Moved all SQLException constructor usage to a factory in SQLError (ground-work for JDBC-4.0 SQLState-based exception classes).
Removed Java5-specific calls to BigDecimal constructor (when result set value is '', (int)0 was being used as an argument indirectly via method return value. This signature doesn't exist prior to Java5.)
Added service-provider entry to META-INF/services/java.sql.Driver for JDBC-4.0 support.
Return "[VAR]BINARY" for RSMD.getColumnTypeName() when that is actually the type, and it can be distinguished (MySQL-4.1 and newer).
When fix for Bug #14562 was merged from 3.1.12, added functionality for CallableStatement's parameter metadata to return correct information for .getParameterClassName().
Fuller synchronization of Connection to avoid deadlocks when using multithreaded frameworks that multithread a single connection (usually not recommended, but the JDBC spec allows it anyways), part of fix to Bug #14972).
Implementation of Statement.cancel() and Statement.setQueryTimeout(). Both require MySQL-5.0.0 or newer server, require a separate connection to issue the KILL QUERY statement, and in the case of setQueryTimeout() creates an additional thread to handle the timeout functionality.
Note: Failures to cancel the statement for setQueryTimeout() may manifest themselves as RuntimeExceptions 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.

23.3.6.5. Changes in MySQL Connector/J 3.1.14 (not yet released)

Fixed updatable result set throws ClassCastException when there is row data and moveToInsertRow() is called. (Fixes Bug#20479)
Fixed Updatable result set that contains a BIT column fails when server-side prepared statements are used. (Fixes Bug#20485)
Fixed memory leak with profileSQL=true. (Fixes Bug#16987)
Connection fails to localhost when using timeout and IPv6 is configured. (Fixes Bug#19726)
Fixed NullPointerException in MysqlDataSourceFactory due to Reference containing RefAddrs with null content. (Fixes Bug#16791)
Fixed ResultSet.getShort() for UNSIGNED TINYINT returns incorrect values when using server-side prepared statements. (Fixes Bug#20306)
Fixed can't pool server-side prepared statements, exception raised when re-using them. (Fixes Bug#20687)
Fixed BUG#21062 - ResultSet.getSomeInteger() doesn't work for BIT(>1).
Fixed BUG#18880 - ResultSet.getFloatFromString() can't retrieve values near Float.MIN/MAX_VALUE.
Fixed BUG#20888 - escape of quotes in client-side prepared statements parsing not respected. Patch covers more than bug report, including NO_BACKSLASH_ESCAPES being set, and stacked quote characters forms of escaping (i.e. '' or "").
Fixed BUG#19993 - ReplicationDriver does not always round-robin load balance depending on URL used for slaves list.

23.3.6.6. Changes in MySQL Connector/J 3.1.13 (26 May 2006)

INOUT parameter does not store IN value. (Bug #15464)
Exception thrown for new decimal type when using updatable result sets. (Bug #14609)
No "dos" character set in MySQL > 4.1.0. (Bug #15544)
PreparedStatement.setObject() serializes BigInteger as object, rather than sending as numeric value (and is thus not complementary to .getObject() on an UNSIGNED LONG type). (Bug #15383)
ResultSet.getShort() for UNSIGNED TINYINT returned wrong values. (Bug #11874)
lib-nodist directory missing from package breaks out-of-box build. (Bug #15676)
DBMD.getColumns() returns wrong type for BIT. (Bug #15854)
Fixed issue where driver was unable to initialize character set mapping tables. Removed reliance on .properties files to hold this information, as it turns out to be too problematic to code around class loader hierarchies that change depending on how an application is deployed. Moved information back into the CharsetMapping class. (Bug #14938)
Fixed updatable result set doesn't return AUTO_INCREMENT values for insertRow() when multiple column primary keys are used. (the driver was checking for the existence of single-column primary keys and an autoincrement value > 0 instead of a straightforward isAutoIncrement() check). (Bug #16841)
Fixed Statement.getGeneratedKeys() throws NullPointerException when no query has been processed. (Bug #17099)
Fixed driver trying to call methods that don't exist on older and newer versions of Log4j. The fix is not trying to auto-detect presense of log4j, too many different incompatible versions out there in the wild to do this reliably. (Bug #13469)
If you relied on autodetection before, you will need to add "logger=com.mysql.jdbc.log.Log4JLogger" to your JDBC URL to enable Log4J usage, or alternatively use the new "CommonsLogger" class to take care of this.
Added support for Apache Commons logging, use "com.mysql.jdbc.log.CommonsLogger" as the value for the "logger" configuration property.
LogFactory now prepends "com.mysql.jdbc.log" to log class name if it can't be found as-specified. This allows you to use "short names" for the built-in log factories, for example "logger=CommonsLogger" instead of "logger=com.mysql.jdbc.log.CommonsLogger".
Fixed issue with ReplicationConnection incorrectly copying state, doesn't transfer connection context correctly when transitioning between the same read-only states. (Bug #15570)
Fixed issue where server-side prepared statements don't cause truncation exceptions to be thrown when truncation happens. (Bug #18041)
Added performance feature, re-writing of batched executes for Statement.executeBatch() (for all DML statements) and PreparedStatement.executeBatch() (for INSERTs with VALUE clauses only). Enable by using "rewriteBatchedStatements=true" in your JDBC URL.
Fixed CallableStatement.registerOutParameter() not working when some parameters pre-populated. Still waiting for feedback from JDBC experts group to determine what correct parameter count from getMetaData() should be, however. (Bug #17898)
Fixed calling clearParameters() on a closed prepared statement causes NPE. (Bug #17587)
Map "latin1" on MySQL server to CP1252 for MySQL > 4.1.0.
Added additional accessor and mutator methods on ConnectionProperties so that DataSource users can use same naming as regular URL properties.
Fixed data truncation and getWarnings() only returns last warning in set. (Bug #18740)
Improved performance of retrieving BigDecimal, Time, Timestamp and Date values from server-side prepared statements by creating fewer short-lived instances of Strings when the native type is not an exact match for the requested type. Fixes Bug #18496 for BigDecimals.
Fixed aliased column names where length of name > 251 are corrupted. (Bug #18554)
Fixed ResultSet.wasNull() not always reset correctly for booleans when done via conversion for server-side prepared statements. (Bug #17450)
Fixed invalid classname returned for ResultSetMetaData.getColumnClassName() for BIGINT type. (Bug #19282)
Fixed case where driver wasn't reading server status correctly when fetching server-side prepared statement rows, which in some cases could cause warning counts to be off, or multiple result sets to not be read off the wire.
Driver now aware of fix for BIT type metadata that went into MySQL-5.0.21 for server not reporting length consistently (Bug #13601).
Fixed PreparedStatement.setObject(int, Object, int) doesn't respect scale of BigDecimals. (Bug #19615)
Fixed ResultSet.wasNull() returns incorrect value when extracting native string from server-side prepared statement generated result set. (Bug #19282)

23.3.6.7. Changes in MySQL Connector/J 3.1.12 (30 November 2005)

Fixed client-side prepared statement bug with embedded ? characters inside quoted identifiers (it was recognized as a placeholder, when it was not).
Don't allow executeBatch() for CallableStatements with registered OUT/INOUT parameters (JDBC compliance).
Fall back to platform-encoding for URLDecoder.decode() when parsing driver URL properties if the platform doesn't have a two-argument version of this method.
Java type conversion may be incorrect for MEDIUMINT. (Bug #14562)
Added configuration property useGmtMillisForDatetimes which when set to true causes ResultSet.getDate(), .getTimestamp() to return correct millis-since GMT when .getTime() is called on the return value (currently default is false for legacy behavior).
Fixed DatabaseMetaData.stores*Identifiers():
- If lower_case_table_names=0 (on server):
  - storesLowerCaseIdentifiers() returns false
  - storesLowerCaseQuotedIdentifiers() returns false
  - storesMixedCaseIdentifiers() returns true
  - storesMixedCaseQuotedIdentifiers() returns true
  - storesUpperCaseIdentifiers() returns false
  - storesUpperCaseQuotedIdentifiers() returns true
- If lower_case_table_names=1 (on server):
  - storesLowerCaseIdentifiers() returns true
  - storesLowerCaseQuotedIdentifiers() returns true
  - storesMixedCaseIdentifiers() returns false
  - storesMixedCaseQuotedIdentifiers() returns false
  - storesUpperCaseIdentifiers() returns false
  - storesUpperCaseQuotedIdentifiers() returns true
DatabaseMetaData.getColumns() doesn't return TABLE_NAME correctly. (Bug #14815)
Escape processor replaces quote character in quoted string with string delimiter. (Bug #14909)
OpenOffice expects DBMD.supportsIntegrityEnhancementFacility() to return true if foreign keys are supported by the datasource, even though this method also covers support for check constraints, which MySQL doesn't have. Setting the configuration property overrideSupportsIntegrityEnhancementFacility to true causes the driver to return true for this method. (Bug #12975)
Added com.mysql.jdbc.testsuite.url.default system property to set default JDBC url for testsuite (to speed up bug resolution when I'm working in Eclipse).
Unable to initialize character set mapping tables (due to J2EE classloader differences). (Bug #14938)
Deadlock while closing server-side prepared statements from multiple threads sharing one connection. (Bug #14972)
logSlowQueries should give better info. (Bug #12230)
Extraneous sleep on autoReconnect. (Bug #13775)
Driver incorrectly closes streams passed as arguments to PreparedStatements. Reverts to legacy behavior by setting the JDBC configuration property autoClosePStmtStreams to true (also included in the 3-0-Compat configuration “bundle”). (Bug #15024)
maxQuerySizeToLog is not respected. Added logging of bound values for execute() phase of server-side prepared statements when profileSQL=true as well. (Bug #13048)
Usage advisor complains about unreferenced columns, even though they've been referenced. (Bug #15065)
Don't increase timeout for failover/reconnect. (Bug #6577)
Process escape tokens in Connection.prepareStatement(...). (Bug #15141) You can disable this behavior by setting the JDBC URL configuration property processEscapeCodesForPrepStmts to false.
Reconnect during middle of executeBatch() should not occur if autoReconnect is enabled. (Bug #13255)

23.3.6.8. Changes in MySQL Connector/J 3.1.11-stable (07 October 2005)

Spurious ! on console when character encoding is utf8. (Bug #11629)
Fixed statements generated for testcases missing ; for “plain” statements.
Incorrect generation of testcase scripts for server-side prepared statements. (Bug #11663)
Fixed regression caused by fix for Bug #11552 that caused driver to return incorrect values for unsigned integers when those integers where within the range of the positive signed type.
Moved source code to Subversion repository.
Escape tokenizer doesn't respect stacked single quotes for escapes. (Bug #11797)
GEOMETRY type not recognized when using server-side prepared statements.
ReplicationConnection won't switch to slave, throws “Catalog can't be null” exception. (Bug #11879)
Properties shared between master and slave with replication connection. (Bug #12218)
Statement.getWarnings() fails with NPE if statement has been closed. (Bug #10630)
Only get char[] from SQL in PreparedStatement.ParseInfo() when needed.
Geometry types not handled with server-side prepared statements. (Bug #12104)
StringUtils.getBytes() doesn't work when using multi-byte character encodings and a length in characters is specified. (Bug #11614)
Pstmt.setObject(...., Types.BOOLEAN) throws exception. (Bug #11798)
maxPerformance.properties mis-spells “elideSetAutoCommits”. (Bug #11976)
DBMD.storesLower/Mixed/UpperIdentifiers() reports incorrect values for servers deployed on Windows. (Bug #11575)
ResultSet.moveToCurrentRow() fails to work when preceded by a call to ResultSet.moveToInsertRow(). (Bug #11190)
VARBINARY data corrupted when using server-side prepared statements and .setBytes(). (Bug #11115)
explainSlowQueries hangs with server-side prepared statements. (Bug #12229)
Escape processor didn't honor strings demarcated with double quotes. (Bug #11498)
Lifted restriction of changing streaming parameters with server-side prepared statements. As long as all streaming parameters were set before execution, .clearParameters() does not have to be called. (due to limitation of client/server protocol, prepared statements can not reset individual stream data on the server side).
Reworked Field class, *Buffer, and MysqlIO to be aware of field lengths > Integer.MAX_VALUE.
Updated DBMD.supportsCorrelatedQueries() to return true for versions > 4.1, supportsGroupByUnrelated() to return true and getResultSetHoldability() to return HOLD_CURSORS_OVER_COMMIT.
Handling of catalog argument in DatabaseMetaData.getIndexInfo(), which also means changes to the following methods in DatabaseMetaData: (Bug #12541)
- getBestRowIdentifier()
- getColumns()
- getCrossReference()
- getExportedKeys()
- getImportedKeys()
- getIndexInfo()
- getPrimaryKeys()
- getProcedures() (and thus indirectly getProcedureColumns())
- getTables()
The catalog argument in all of these methods now behaves in the following way:
- Specifying NULL means that catalog will not be used to filter the results (thus all databases will be searched), unless you've set nullCatalogMeansCurrent=true in your JDBC URL properties.
- Specifying "" means “current” catalog, even though this isn't quite JDBC spec compliant, it's there for legacy users.
- Specifying a catalog works as stated in the API docs.
- Made Connection.clientPrepare() available from “wrapped” connections in the jdbc2.optional package (connections built by ConnectionPoolDataSource instances).
Added Connection.isMasterConnection() for clients to be able to determine if a multi-host master/slave connection is connected to the first host in the list.
Tokenizer for = in URL properties was causing sessionVariables=.... to be parameterized incorrectly. (Bug #12753)
Foreign key information that is quoted is parsed incorrectly when DatabaseMetaData methods use that information. (Bug #11781)
The sendBlobChunkSize property is now clamped to max_allowed_packet with consideration of stream buffer size and packet headers to avoid PacketTooBigExceptions when max_allowed_packet is similar in size to the default sendBlobChunkSize which is 1M.
CallableStatement.clearParameters() now clears resources associated with INOUT/OUTPUT parameters as well as INPUT parameters.
Connection.prepareCall() is database name case-sensitive (on Windows systems). (Bug #12417)
cp1251 incorrectly mapped to win1251 for servers newer than 4.0.x. (Bug #12752)
java.sql.Types.OTHER returned for BINARY and VARBINARY columns when using DatabaseMetaData.getColumns(). (Bug #12970)
ServerPreparedStatement.getBinding() now checks if the statement is closed before attempting to reference the list of parameter bindings, to avoid throwing a NullPointerException.
ResultSetMetaData from Statement.getGeneratedKeys() caused a NullPointerException to be thrown whenever a method that required a connection reference was called. (Bug #13277)
Backport of Field class, ResultSetMetaData.getColumnClassName(), and ResultSet.getObject(int) changes from 5.0 branch to fix behavior surrounding VARCHAR BINARY/VARBINARY and related types.
Fixed NullPointerException when converting catalog parameter in many DatabaseMetaDataMethods to byte[]s (for the result set) when the parameter is null. (null isn't technically allowed by the JDBC specification, but we've historically allowed it).
Backport of VAR[BINARY|CHAR] [BINARY] types detection from 5.0 branch.
Read response in MysqlIO.sendFileToServer(), even if the local file can't be opened, otherwise next query issued will fail, because it's reading the response to the empty LOAD DATA INFILE packet sent to the server.
Workaround for Bug #13374: ResultSet.getStatement() on closed result set returns NULL (as per JDBC 4.0 spec, but not backward-compatible). Set the connection property retainStatementAfterResultSetClose to true to be able to retrieve a ResultSet's statement after the ResultSet has been closed via .getStatement() (the default is false, to be JDBC-compliant and to reduce the chance that code using JDBC leaks Statement instances).
URL configuration parameters don't allow ‘&’ or ‘=’ in their values. The JDBC driver now parses configuration parameters as if they are encoded using the application/x-www-form-urlencoded format as specified by java.net.URLDecoder (http://java.sun.com/j2se/1.5.0/docs/api/java/net/URLDecoder.html). (Bug #13453)
If the ‘%’ character is present in a configuration property, it must now be represented as %25, which is the encoded form of ‘%’ when using application/x-www-form-urlencoded encoding.
The configuration property sessionVariables now allows you to specify variables that start with the ‘@’ sign.
When gatherPerfMetrics is enabled for servers older than 4.1.0, a NullPointerException is thrown from the constructor of ResultSet if the query doesn't use any tables. (Bug #13043)

23.3.6.9. Changes in MySQL Connector/J 3.1.10-stable (23 June 2005)

Fixed connecting without a database specified raised an exception in MysqlIO.changeDatabaseTo().
Initial implemention of ParameterMetadata for PreparedStatement.getParameterMetadata(). Only works fully for CallableStatements, as current server-side prepared statements return every parameter as a VARCHAR type.

23.3.6.10. Changes in MySQL Connector/J 3.1.9-stable (22 June 2005)

Overhaul of character set configuration, everything now lives in a properties file.
Driver now correctly uses CP932 if available on the server for Windows-31J, CP932 and MS932 java encoding names, otherwise it resorts to SJIS, which is only a close approximation. Currently only MySQL-5.0.3 and newer (and MySQL-4.1.12 or .13, depending on when the character set gets backported) can reliably support any variant of CP932.
com.mysql.jdbc.PreparedStatement.ParseInfo does unnecessary call to toCharArray(). (Bug #9064)
Memory leak in ServerPreparedStatement if serverPrepare() fails. (Bug #10144)
Actually write manifest file to correct place so it ends up in the binary jar file.
Added createDatabaseIfNotExist property (default is false), which will cause the driver to ask the server to create the database specified in the URL if it doesn't exist. You must have the appropriate privileges for database creation for this to work.
Unsigned SMALLINT treated as signed for ResultSet.getInt(), fixed all cases for UNSIGNED integer values and server-side prepared statements, as well as ResultSet.getObject() for UNSIGNED TINYINT. (Bug #10156)
Double quotes not recognized when parsing client-side prepared statements. (Bug #10155)
Made enableStreamingResults() visible on com.mysql.jdbc.jdbc2.optional.StatementWrapper.
Made ServerPreparedStatement.asSql() work correctly so auto-explain functionality would work with server-side prepared statements.
Made JDBC2-compliant wrappers public in order to allow access to vendor extensions.
Cleaned up logging of profiler events, moved code to dump a profiler event as a string to com.mysql.jdbc.log.LogUtils so that third parties can use it.
DatabaseMetaData.supportsMultipleOpenResults() now returns true. The driver has supported this for some time, DBMD just missed that fact.
Driver doesn't support {?=CALL(...)} for calling stored functions. This involved adding support for function retrieval to DatabaseMetaData.getProcedures() and getProcedureColumns() as well. (Bug #10310)
SQLException thrown when retrieving YEAR(2) with ResultSet.getString(). The driver will now always treat YEAR types as java.sql.Dates and return the correct values for getString(). Alternatively, the yearIsDateType connection property can be set to false and the values will be treated as SHORTs. (Bug #10485)
The datatype returned for TINYINT(1) columns when tinyInt1isBit=true (the default) can be switched between Types.BOOLEAN and Types.BIT using the new configuration property transformedBitIsBoolean, which defaults to false. If set to false (the default), DatabaseMetaData.getColumns() and ResultSetMetaData.getColumnType() will return Types.BOOLEAN for TINYINT(1) columns. If true, Types.BOOLEAN will be returned instead. Regardless of this configuration property, if tinyInt1isBit is enabled, columns with the type TINYINT(1) will be returned as java.lang.Boolean instances from ResultSet.getObject(...), and ResultSetMetaData.getColumnClassName() will return java.lang.Boolean.
SQLException is thrown when using property characterSetResults with cp932 or eucjpms. (Bug #10496)
Reorganized directory layout. Sources now are in src folder. Don't pollute parent directory when building, now output goes to ./build, distribution goes to ./dist.
Added support/bug hunting feature that generates .sql test scripts to STDERR when autoGenerateTestcaseScript is set to true.
0-length streams not sent to server when using server-side prepared statements. (Bug #10850)
Setting cachePrepStmts=true now causes the Connection to also cache the check the driver performs to determine if a prepared statement can be server-side or not, as well as caches server-side prepared statements for the lifetime of a connection. As before, the prepStmtCacheSize parameter controls the size of these caches.
Try to handle OutOfMemoryErrors more gracefully. Although not much can be done, they will in most cases close the connection they happened on so that further operations don't run into a connection in some unknown state. When an OOM has happened, any further operations on the connection will fail with a “Connection closed” exception that will also list the OOM exception as the reason for the implicit connection close event.
Don't send COM_RESET_STMT for each execution of a server-side prepared statement if it isn't required.
Driver detects if you're running MySQL-5.0.7 or later, and does not scan for LIMIT ?[,?] in statements being prepared, as the server supports those types of queries now.
VARBINARY data corrupted when using server-side prepared statements and ResultSet.getBytes(). (Bug #11115)
Connection.setCatalog() is now aware of the useLocalSessionState configuration property, which when set to true will prevent the driver from sending USE ... to the server if the requested catalog is the same as the current catalog.
Added the following configuration bundles, use one or many via the useConfigs configuration property:
- maxPerformance — maximum performance without being reckless
- solarisMaxPerformance — maximum performance for Solaris, avoids syscalls where it can
- 3-0-Compat — Compatibility with Connector/J 3.0.x functionality
Added maintainTimeStats configuration property (defaults to true), which tells the driver whether or not to keep track of the last query time and the last successful packet sent to the server's time. If set to false, removes two syscalls per query.
autoReconnect ping causes exception on connection startup. (Bug #11259)
Connector/J dumping query into SQLException twice. (Bug #11360)
Fixed PreparedStatement.setClob() not accepting null as a parameter.
Production package doesn't include JBoss integration classes. (Bug #11411)
Removed nonsensical “costly type conversion” warnings when using usage advisor.

23.3.6.11. Changes in MySQL Connector/J 3.1.8-stable (14 April 2005)

Fixed DatabaseMetaData.getTables() returning views when they were not asked for as one of the requested table types.
Added support for new precision-math DECIMAL type in MySQL 5.0.3 and up.
Fixed ResultSet.getTime() on a NULL value for server-side prepared statements throws NPE.
Made Connection.ping() a public method.
DATE_FORMAT() queries returned as BLOBs from getObject(). (Bug #8868)
ServerPreparedStatements now correctly “stream” BLOB/CLOB data to the server. You can configure the threshold chunk size using the JDBC URL property blobSendChunkSize (the default is 1MB).
BlobFromLocator now uses correct identifier quoting when generating prepared statements.
Server-side session variables can be preset at connection time by passing them as a comma-delimited list for the connection property sessionVariables.
Fixed regression in ping() for users using autoReconnect=true.
PreparedStatement.addBatch() doesn't work with server-side prepared statements and streaming BINARY data. (Bug #9040)
DBMD.supportsMixedCase*Identifiers() returns wrong value on servers running on case-sensitive filesystems. (Bug #8800)
Cannot use UTF-8 for characterSetResults configuration property. (Bug #9206)
A continuation of Bug #8868, where functions used in queries that should return non-string types when resolved by temporary tables suddenly become opaque binary strings (work-around for server limitation). Also fixed fields with type of CHAR(n) CHARACTER SET BINARY to return correct/matching classes for RSMD.getColumnClassName() and ResultSet.getObject(). (Bug #9236)
DBMD.supportsResultSetConcurrency() not returning true for forward-only/read-only result sets (we obviously support this). (Bug #8792)
DATA_TYPE column from DBMD.getBestRowIdentifier() causes ArrayIndexOutOfBoundsException when accessed (and in fact, didn't return any value). (Bug #8803)
Check for empty strings ('') when converting CHAR/VARCHAR column data to numbers, throw exception if emptyStringsConvertToZero configuration property is set to false (for backward-compatibility with 3.0, it is now set to true by default, but will most likely default to false in 3.2).
PreparedStatement.getMetaData() inserts blank row in database under certain conditions when not using server-side prepared statements. (Bug #9320)
Connection.canHandleAsPreparedStatement() now makes “best effort” to distinguish LIMIT clauses with placeholders in them from ones without in order to have fewer false positives when generating work-arounds for statements the server cannot currently handle as server-side prepared statements.
Fixed build.xml to not compile log4j logging if log4j not available.
Added support for the c3p0 connection pool's (http://c3p0.sf.net/) validation/connection checker interface which uses the lightweight COM_PING call to the server if available. To use it, configure your c3p0 connection pool's connectionTesterClassName property to use com.mysql.jdbc.integration.c3p0.MysqlConnectionTester.
Better detection of LIMIT inside/outside of quoted strings so that the driver can more correctly determine whether a prepared statement can be prepared on the server or not.
Stored procedures with same name in different databases confuse the driver when it tries to determine parameter counts/types. (Bug #9319)
Added finalizers to ResultSet and Statement implementations to be JDBC spec-compliant, which requires that if not explicitly closed, these resources should be closed upon garbage collection.
Stored procedures with DECIMAL parameters with storage specifications that contained ‘,’ in them would fail. (Bug #9682)
PreparedStatement.setObject(int, Object, int type, int scale) now uses scale value for BigDecimal instances.
Statement.getMoreResults() could throw NPE when existing result set was .close()d. (Bug #9704)
The performance metrics feature now gathers information about number of tables referenced in a SELECT.
The logging system is now automatically configured. If the value has been set by the user, via the URL property logger or the system property com.mysql.jdbc.logger, then use that, otherwise, autodetect it using the following steps:
1. Log4j, if it's available,
2. Then JDK1.4 logging,
3. Then fallback to our STDERR logging.
DBMD.getTables() shouldn't return tables if views are asked for, even if the database version doesn't support views. (Bug #9778)
Fixed driver not returning true for -1 when ResultSet.getBoolean() was called on result sets returned from server-side prepared statements.
Added a Manifest.MF file with implementation information to the .jar file.
More tests in Field.isOpaqueBinary() to distinguish opaque binary (that is, fields with type CHAR(n) and CHARACTER SET BINARY) from output of various scalar and aggregate functions that return strings.
Should accept null for catalog (meaning use current) in DBMD methods, even though it's not JDBC-compliant for legacy's sake. Disable by setting connection property nullCatalogMeansCurrent to false (which will be the default value in C/J 3.2.x). (Bug #9917)
Should accept null for name patterns in DBMD (meaning ‘%’), even though it isn't JDBC compliant, for legacy's sake. Disable by setting connection property nullNamePatternMatchesAll to false (which will be the default value in C/J 3.2.x). (Bug #9769)

23.3.6.12. Changes in MySQL Connector/J 3.1.7-stable (18 February 2005)

Timestamp key column data needed _binary stripped for UpdatableResultSet.refreshRow(). (Bug #7686)
Timestamps converted incorrectly to strings with server-side prepared statements and updatable result sets. (Bug #7715)
Detect new sql_mode variable in string form (it used to be integer) and adjust quoting method for strings appropriately.
Added holdResultsOpenOverStatementClose property (default is false), that keeps result sets open over statement.close() or new execution on same statement (suggested by Kevin Burton).
Infinite recursion when “falling back” to master in failover configuration. (Bug #7952)
Disable multi-statements (if enabled) for MySQL-4.1 versions prior to version 4.1.10 if the query cache is enabled, as the server returns wrong results in this configuration.
Fixed duplicated code in configureClientCharset() that prevented useOldUTF8Behavior=true from working properly.
Removed dontUnpackBinaryResults functionality, the driver now always stores results from server-side prepared statements as is from the server and unpacks them on demand.
Emulated locators corrupt binary data when using server-side prepared statements. (Bug #8096)
Fixed synchronization issue with ServerPreparedStatement.serverPrepare() that could cause deadlocks/crashes if connection was shared between threads.
By default, the driver now scans SQL you are preparing via 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 by passing emulateUnsupportedPstmts=false in your JDBC URL. (Bug #4718)
Remove _binary introducer from parameters used as in/out parameters in CallableStatement.
Always return byte[]s for output parameters registered as *BINARY.
Send correct value for “boolean” true to server for PreparedStatement.setObject(n, "true", Types.BIT).
Fixed bug with Connection not caching statements from prepareStatement() when the statement wasn't a server-side prepared statement.
Choose correct “direction” to apply time adjustments when both client and server are in GMT time zone when using ResultSet.get(..., cal) and PreparedStatement.set(...., cal).
Added dontTrackOpenResources option (default is false, to be JDBC compliant), which helps with memory use for non-well-behaved apps (that is, applications that don't close Statement objects when they should).
ResultSet.getString() doesn't maintain format stored on server, bug fix only enabled when noDatetimeStringSync property is set to true (the default is false). (Bug #8428)
Fixed NPE in ResultSet.realClose() when using usage advisor and result set was already closed.
PreparedStatements not creating streaming result sets. (Bug #8487)
Don't pass NULL to String.valueOf() in ResultSet.getNativeConvertToString(), as it stringifies it (that is, returns null), which is not correct for the method in question.
ResultSet.getBigDecimal() throws exception when rounding would need to occur to set scale. The driver now chooses a rounding mode of “half up” if non-rounding BigDecimal.setScale() fails. (Bug #8424)
Added useLocalSessionState configuration property, when set to true the JDBC driver trusts that the application is well-behaved and only sets autocommit and transaction isolation levels using the methods provided on java.sql.Connection, and therefore can manipulate these values in many cases without incurring round-trips to the database server.
Added enableStreamingResults() to Statement for connection pool implementations that check Statement.setFetchSize() for specification-compliant values. Call Statement.setFetchSize(>=0) to disable the streaming results for that statement.
Added support for BIT type in MySQL-5.0.3. The driver will treat BIT(1-8) as the JDBC standard BIT type (which maps to java.lang.Boolean), as the server does not currently send enough information to determine the size of a bitfield when < 9 bits are declared. BIT(>9) will be treated as VARBINARY, and will return byte[] when getObject() is called.

23.3.6.13. Changes in MySQL Connector/J 3.1.6-stable (23 December 2004)

Fixed hang on SocketInputStream.read() with Statement.setMaxRows() and multiple result sets when driver has to truncate result set directly, rather than tacking a LIMIT n on the end of it.
DBMD.getProcedures() doesn't respect catalog parameter. (Bug #7026)

23.3.6.14. Changes in MySQL Connector/J 3.1.5-gamma (02 December 2004)

Fix comparisons made between string constants and dynamic strings that are converted with either toUpperCase() or toLowerCase() to use Locale.ENGLISH, as some locales “override” case rules for English. Also use StringUtils.indexOfIgnoreCase() instead of .toUpperCase().indexOf(), avoids creating a very short-lived transient String instance.
Server-side prepared statements did not honor zeroDateTimeBehavior property, and would cause class-cast exceptions when using ResultSet.getObject(), as the all-zero string was always returned. (Bug #5235)
Fixed batched updates with server prepared statements weren't looking if the types had changed for a given batched set of parameters compared to the previous set, causing the server to return the error “Wrong arguments to mysql_stmt_execute()”.
Handle case when string representation of timestamp contains trailing ‘.’ with no numbers following it.
Inefficient detection of pre-existing string instances in ResultSet.getNativeString(). (Bug #5706)
Don't throw exceptions for Connection.releaseSavepoint().
Use a per-session Calendar instance by default when decoding dates from ServerPreparedStatements (set to old, less performant behavior by setting property dynamicCalendars=true).
Added experimental configuration property dontUnpackBinaryResults, which delays unpacking binary result set values until they're asked for, and only creates object instances for non-numerical values (it is set to false by default). For some usecase/jvm combinations, this is friendlier on the garbage collector.
UNSIGNED BIGINT unpacked incorrectly from server-side prepared statement result sets. (Bug #5729)
ServerSidePreparedStatement allocating short-lived objects unnecessarily. (Bug #6225)
Removed unwanted new Throwable() in ResultSet constructor due to bad merge (caused a new object instance that was never used for every result set created). Found while profiling for Bug #6359.
Fixed too-early creation of StringBuffer in EscapeProcessor.escapeSQL(), also return String when escaping not needed (to avoid unnecessary object allocations). Found while profiling for Bug #6359.
Use null-safe-equals for key comparisons in updatable result sets.
SUM() on DECIMAL with server-side prepared statement ignores scale if zero-padding is needed (this ends up being due to conversion to DOUBLE by server, which when converted to a string to parse into BigDecimal, loses all “padding” zeros). (Bug #6537)
Use DatabaseMetaData.getIdentifierQuoteString() when building DBMD queries.
Use 1MB packet for sending file for LOAD DATA LOCAL INFILE if that is < max_allowed_packet on server.
ResultSetMetaData.getColumnDisplaySize() returns incorrect values for multi-byte charsets. (Bug #6399)
Make auto-deserialization of java.lang.Objects stored in BLOB columns configurable via autoDeserialize property (defaults to false).
Re-work Field.isOpaqueBinary() to detect CHAR(n) CHARACTER SET BINARY to support fixed-length binary fields for ResultSet.getObject().
Use our own implementation of buffered input streams to get around blocking behavior of java.io.BufferedInputStream. Disable this with useReadAheadInput=false.
Failing to connect to the server when one of the addresses for the given host name is IPV6 (which the server does not yet bind on). The driver now loops through all IP addresses for a given host, and stops on the first one that accepts() a socket.connect(). (Bug #6348)

23.3.6.15. Changes in MySQL Connector/J 3.1.4-beta (04 September 2004)

Connector/J 3.1.3 beta does not handle integers correctly (caused by changes to support unsigned reads in Buffer.readInt() -> Buffer.readShort()). (Bug #4510)
Added support in DatabaseMetaData.getTables() and getTableTypes() for views, which are now available in MySQL server 5.0.x.
ServerPreparedStatement.execute*() sometimes threw ArrayIndexOutOfBoundsException when unpacking field metadata. (Bug #4642)
Optimized integer number parsing, enable “old” slower integer parsing using JDK classes via useFastIntParsing=false property.
Added useOnlyServerErrorMessages property, which causes message text in exceptions generated by the server to only contain the text sent by the server (as opposed to the SQLState's “standard” description, followed by the server's error message). This property is set to true by default.
ResultSet.wasNull() does not work for primatives if a previous null was returned. (Bug #4689)
Track packet sequence numbers if enablePacketDebug=true, and throw an exception if packets received out-of-order.
ResultSet.getObject() returns wrong type for strings when using prepared statements. (Bug #4482)
Calling MysqlPooledConnection.close() twice (even though an application error), caused NPE. Fixed.
ServerPreparedStatements dealing with return of DECIMAL type don't work. (Bug #5012)
ResultSet.getObject() doesn't return type Boolean for pseudo-bit types from prepared statements on 4.1.x (shortcut for avoiding extra type conversion when using binary-encoded result sets obscured test in getObject() for “pseudo” bit type). (Bug #5032)
You can now use URLs in LOAD DATA LOCAL INFILE statements, and the driver will use Java's built-in handlers for retreiving the data and sending it to the server. This feature is not enabled by default, you must set the allowUrlInLocalInfile connection property to true.
The driver is more strict about truncation of numerics on ResultSet.get*(), and will throw an SQLException when truncation is detected. You can disable this by setting jdbcCompliantTruncation to false (it is enabled by default, as this functionality is required for JDBC compliance).
Added three ways to deal with all-zero datetimes when reading them from a ResultSet: exception (the default), which throws an SQLException with an SQLState of S1009; convertToNull, which returns NULL instead of the date; and round, which rounds the date to the nearest closest value which is '0001-01-01'.
Fixed ServerPreparedStatement to read prepared statement metadata off the wire, even though it's currently a placeholder instead of using MysqlIO.clearInputStream() which didn't work at various times because data wasn't available to read from the server yet. This fixes sporadic errors users were having with ServerPreparedStatements throwing ArrayIndexOutOfBoundExceptions.
Use com.mysql.jdbc.Message's classloader when loading resource bundle, should fix sporadic issues when the caller's classloader can't locate the resource bundle.

23.3.6.16. Changes in MySQL Connector/J 3.1.3-beta (07 July 2004)

Mangle output parameter names for CallableStatements so they will not clash with user variable names.
Added support for INOUT parameters in CallableStatements.
Null bitmask sent for server-side prepared statements was incorrect. (Bug #4119)
Use SQL Standard SQL states by default, unless useSqlStateCodes property is set to false.
Added packet debuging code (see the enablePacketDebug property documentation).
Added constants for MySQL error numbers (publicly accessible, see com.mysql.jdbc.MysqlErrorNumbers), and the ability to generate the mappings of vendor error codes to SQLStates that the driver uses (for documentation purposes).
Externalized more messages (on-going effort).
Error in retrieval of mediumint column with prepared statements and binary protocol. (Bug #4311)
Support new time zone variables in MySQL-4.1.3 when useTimezone=true.
Support for unsigned numerics as return types from prepared statements. This also causes a change in ResultSet.getObject() for the bigint unsigned type, which used to return BigDecimal instances, it now returns instances of java.lang.BigInteger.

23.3.6.17. Changes in MySQL Connector/J 3.1.2-alpha (09 June 2004)

Fixed stored procedure parameter parsing info when size was specified for a parameter (for example, char(), varchar()).
Enabled callable statement caching via cacheCallableStmts property.
Fixed case when no output parameters specified for a stored procedure caused a bogus query to be issued to retrieve out parameters, leading to a syntax error from the server.
Fixed case when no parameters could cause a NullPointerException in CallableStatement.setOutputParameters().
Removed wrapping of exceptions in MysqlIO.changeUser().
Fixed sending of split packets for large queries, enabled nio ability to send large packets as well.
Added .toString() functionality to ServerPreparedStatement, which should help if you're trying to debug a query that is a prepared statement (it shows SQL as the server would process).
Added gatherPerformanceMetrics property, along with properties to control when/where this info gets logged (see docs for more info).
ServerPreparedStatements weren't actually de-allocating server-side resources when .close() was called.
Added logSlowQueries property, along with slowQueriesThresholdMillis property to control when a query should be considered “slow.”
Correctly map output parameters to position given in prepareCall() versus. order implied during registerOutParameter(). (Bug #3146)
Correctly detect initial character set for servers >= 4.1.0.
Cleaned up detection of server properties.
Support placeholder for parameter metadata for server >= 4.1.2.
getProcedures() does not return any procedures in result set. (Bug #3539)
getProcedureColumns() doesn't work with wildcards for procedure name. (Bug #3540)
DBMD.getSQLStateType() returns incorrect value. (Bug #3520)
Added connectionCollation property to cause driver to issue set collation_connection=... query on connection init if default collation for given charset is not appropriate.
Fixed DatabaseMetaData.getProcedures() when run on MySQL-5.0.0 (output of SHOW PROCEDURE STATUS changed between 5.0.0 and 5.0.1.
getWarnings() returns SQLWarning instead of DataTruncation. (Bug #3804)
Don't enable server-side prepared statements for server version 5.0.0 or 5.0.1, as they aren't compatible with the '4.1.2+' style that the driver uses (the driver expects information to come back that isn't there, so it hangs).

23.3.6.18. Changes in MySQL Connector/J 3.1.1-alpha (14 February 2004)

Fixed bug with UpdatableResultSets not using client-side prepared statements.
Fixed character encoding issues when converting bytes to ASCII when MySQL doesn't provide the character set, and the JVM is set to a multi-byte encoding (usually affecting retrieval of numeric values).
Unpack “unknown” data types from server prepared statements as Strings.
Implemented long data (Blobs, Clobs, InputStreams, Readers) for server prepared statements.
Implemented Statement.getWarnings() for MySQL-4.1 and newer (using SHOW WARNINGS).
Default result set type changed to TYPE_FORWARD_ONLY (JDBC compliance).
Centralized setting of result set type and concurrency.
Refactored how connection properties are set and exposed as DriverPropertyInfo as well as Connection and DataSource properties.
Support for NIO. Use useNIO=true on platforms that support NIO.
Support for transaction savepoints (MySQL >= 4.0.14 or 4.1.1).
Support for mysql_change_user(). See the changeUser() method in com.mysql.jdbc.Connection.
Reduced number of methods called in average query to be more efficient.
Prepared Statements will be re-prepared on auto-reconnect. Any errors encountered are postponed until first attempt to re-execute the re-prepared statement.
Ensure that warnings are cleared before executing queries on prepared statements, as-per JDBC spec (now that we support warnings).
Support “old” profileSql capitalization in ConnectionProperties. This property is deprecated, you should use profileSQL if possible.
Optimized Buffer.readLenByteArray() to return shared empty byte array when length is 0.
Allow contents of PreparedStatement.setBlob() to be retained between calls to .execute*().
Deal with 0-length tokens in EscapeProcessor (caused by callable statement escape syntax).
Check for closed connection on delete/update/insert row operations in UpdatableResultSet.
Fix support for table aliases when checking for all primary keys in UpdatableResultSet.
Removed useFastDates connection property.
Correctly initialize datasource properties from JNDI Refs, including explicitly specified URLs.
DatabaseMetaData now reports supportsStoredProcedures() for MySQL versions >= 5.0.0
Fixed stack overflow in Connection.prepareCall() (bad merge).
Fixed IllegalAccessError to Calendar.getTimeInMillis() in DateTimeValue (for JDK < 1.4).
DatabaseMetaData.getColumns() is not returning correct column ordinal info for non-'%' column name patterns. (Bug #1673)
Merged fix of datatype mapping from MySQL type FLOAT to java.sql.Types.REAL from 3.0 branch.
Detect collation of column for RSMD.isCaseSensitive().
Fixed sending of queries larger than 16M.
Added named and indexed input/output parameter support to CallableStatement. MySQL-5.0.x or newer.
Fixed NullPointerException in ServerPreparedStatement.setTimestamp(), as well as year and month descrepencies in ServerPreparedStatement.setTimestamp(), setDate().
Added ability to have multiple database/JVM targets for compliance and regression/unit tests in build.xml.
Fixed NPE and year/month bad conversions when accessing some datetime functionality in ServerPreparedStatements and their resultant result sets.
Display where/why a connection was implicitly closed (to aid debugging).
CommunicationsException implemented, that tries to determine why communications was lost with a server, and displays possible reasons when .getMessage() is called.
NULL values for numeric types in binary encoded result sets causing NullPointerExceptions. (Bug #2359)
Implemented Connection.prepareCall(), and DatabaseMetaData. getProcedures() and getProcedureColumns().
Reset long binary parameters in ServerPreparedStatement when clearParameters() is called, by sending COM_RESET_STMT to the server.
Merged prepared statement caching, and .getMetaData() support from 3.0 branch.
Fixed off-by-1900 error in some cases for years in TimeUtil.fastDate/TimeCreate() when unpacking results from server-side prepared statements.
Fixed charset conversion issue in getTables(). (Bug #2502)
Implemented multiple result sets returned from a statement or stored procedure.
Server-side prepared statements were not returning datatype YEAR correctly. (Bug #2606)
Enabled streaming of result sets from server-side prepared statements.
Class-cast exception when using scrolling result sets and server-side prepared statements. (Bug #2623)
Merged unbuffered input code from 3.0.
Fixed ConnectionProperties that weren't properly exposed via accessors, cleaned up ConnectionProperties code.
NULL fields were not being encoded correctly in all cases in server-side prepared statements. (Bug #2671)
Fixed rare buffer underflow when writing numbers into buffers for sending prepared statement execution requests.
Use DocBook version of docs for shipped versions of drivers.

23.3.6.19. Changes in MySQL Connector/J 3.1.0-alpha (18 February 2003)

Added requireSSL property.
Added useServerPrepStmts property (default false). The driver will use server-side prepared statements when the server version supports them (4.1 and newer) when this property is set to true. It is currently set to false by default until all bind/fetch functionality has been implemented. Currently only DML prepared statements are implemented for 4.1 server-side prepared statements.
Track open Statements, close all when Connection.close() is called (JDBC compliance).

23.3.6.20. Changes in MySQL Connector/J 3.0.17-ga (23 June 2005)

Timestamp/Time conversion goes in the wrong “direction” when useTimeZone=true and server time zone differs from client time zone. (Bug #5874)
DatabaseMetaData.getIndexInfo() ignored unique parameter. (Bug #7081)
Support new protocol type MYSQL_TYPE_VARCHAR.
Added useOldUTF8Behavior' configuration property, which causes JDBC driver to act like it did with MySQL-4.0.x and earlier when the character encoding is utf-8 when connected to MySQL-4.1 or newer.
Statements created from a pooled connection were returning physical connection instead of logical connection when getConnection() was called. (Bug #7316)
PreparedStatements don't encode Big5 (and other multi-byte) character sets correctly in static SQL strings. (Bug #7033)
Connections starting up failed-over (due to down master) never retry master. (Bug #6966)
PreparedStatement.fixDecimalExponent() adding extra +, making number unparseable by MySQL server. (Bug #7061)
Timestamp key column data needed _binary stripped for UpdatableResultSet.refreshRow(). (Bug #7686)
Backported SQLState codes mapping from Connector/J 3.1, enable with useSqlStateCodes=true as a connection property, it defaults to false in this release, so that we don't break legacy applications (it defaults to true starting with Connector/J 3.1).
PreparedStatement.fixDecimalExponent() adding extra +, making number unparseable by MySQL server. (Bug #7601)
Escape sequence {fn convert(..., type)} now supports ODBC-style types that are prepended by SQL_.
Fixed duplicated code in configureClientCharset() that prevented useOldUTF8Behavior=true from working properly.
Handle streaming result sets with more than 2 billion rows properly by fixing wraparound of row number counter.
MS932, SHIFT_JIS, and Windows_31J not recognized as aliases for sjis. (Bug #7607)
Adding CP943 to aliases for sjis. (Bug #6549, fixed while fixing Bug #7607)
Which requires hex escaping of binary data when using multi-byte charsets with prepared statements. (Bug #8064)
NON_UNIQUE column from DBMD.getIndexInfo() returned inverted value. (Bug #8812)
Workaround for server Bug #9098: Default values of CURRENT_* for DATE, TIME, DATETIME, and TIMESTAMP columns can't be distinguished from string values, so UpdatableResultSet.moveToInsertRow() generates bad SQL for inserting default values.
EUCKR charset is sent as SET NAMES euc_kr which MySQL-4.1 and newer doesn't understand. (Bug #8629)
DatabaseMetaData.supportsSelectForUpdate() returns correct value based on server version.
Use hex escapes for PreparedStatement.setBytes() for double-byte charsets including “aliases” Windows-31J, CP934, MS932.
Added support for the EUC_JP_Solaris character encoding, which maps to a MySQL encoding of eucjpms (backported from 3.1 branch). This only works on servers that support eucjpms, namely 5.0.3 or later.

23.3.6.21. Changes in MySQL Connector/J 3.0.16-ga (15 November 2004)

Re-issue character set configuration commands when re-using pooled connections and/or Connection.changeUser() when connected to MySQL-4.1 or newer.
Fixed ResultSetMetaData.isReadOnly() to detect non-writable columns when connected to MySQL-4.1 or newer, based on existence of “original” table and column names.
ResultSet.updateByte() when on insert row throws ArrayOutOfBoundsException. (Bug #5664)
Fixed DatabaseMetaData.getTypes() returning incorrect (this is, non-negative) scale for the NUMERIC type.
Off-by-one bug in Buffer.readString(string). (Bug #5664)
Made TINYINT(1) -> BIT/Boolean conversion configurable via tinyInt1isBit property (default true to be JDBC compliant out of the box).
Only set character_set_results during connection establishment if server version >= 4.1.1.
Fixed regression where useUnbufferedInput was defaulting to false.
ResultSet.getTimestamp() on a column with TIME in it fails. (Bug #5664)

23.3.6.22. Changes in MySQL Connector/J 3.0.15-production (04 September 2004)

StringUtils.escapeEasternUnicodeByteStream was still broken for GBK. (Bug #4010)
Failover for autoReconnect not using port numbers for any hosts, and not retrying all hosts. (Warning: This required a change to the SocketFactory connect() method signature, which is now public Socket connect(String host, int portNumber, Properties props); therefore, any third-party socket factories will have to be changed to support this signature. (Bug #4334)
Logical connections created by MysqlConnectionPoolDataSource will now issue a rollback() when they are closed and sent back to the pool. If your application server/connection pool already does this for you, you can set the rollbackOnPooledClose property to false to avoid the overhead of an extra rollback().
Removed redundant calls to checkRowPos() in ResultSet.
DOUBLE mapped twice in DBMD.getTypeInfo(). (Bug #4742)
Added FLOSS license exemption.
Calling .close() twice on a PooledConnection causes NPE. (Bug #4808)
DBMD.getColumns() returns incorrect JDBC type for unsigned columns. This affects type mappings for all numeric types in the RSMD.getColumnType() and RSMD.getColumnTypeNames() methods as well, to ensure that “like” types from DBMD.getColumns() match up with what RSMD.getColumnType() and getColumnTypeNames() return. (Bug #4138, Bug #4860)
“Production” is now “GA” (General Availability) in naming scheme of distributions.
RSMD.getPrecision() returning 0 for non-numeric types (should return max length in chars for non-binary types, max length in bytes for binary types). This fix also fixes mapping of RSMD.getColumnType() and RSMD.getColumnTypeName() for the BLOB types based on the length sent from the server (the server doesn't distinguish between TINYBLOB, BLOB, MEDIUMBLOB or LONGBLOB at the network protocol level). (Bug #4880)
ResultSet should release Field[] instance in .close(). (Bug #5022)
ResultSet.getMetaData() should not return incorrectly initialized metadata if the result set has been closed, but should instead throw an SQLException. Also fixed for getRow() and getWarnings() and traversal methods by calling checkClosed() before operating on instance-level fields that are nullified during .close(). (Bug #5069)
Parse new time zone variables from 4.1.x servers.
Use _binary introducer for PreparedStatement.setBytes() and set*Stream() when connected to MySQL-4.1.x or newer to avoid misinterpretation during character conversion.

23.3.6.23. Changes in MySQL Connector/J 3.0.14-production (28 May 2004)

Fixed URL parsing error.

23.3.6.24. Changes in MySQL Connector/J 3.0.13-production (27 May 2004)

Using a MySQLDatasource without server name fails. (Bug #3848)
No Database Selected when using MysqlConnectionPoolDataSource. (Bug #3920)
PreparedStatement.getGeneratedKeys() method returns only 1 result for batched insertions. (Bug #3873)

23.3.6.25. Changes in MySQL Connector/J 3.0.12-production (18 May 2004)

Add unsigned attribute to DatabaseMetaData.getColumns() output in the TYPE_NAME column.
Added failOverReadOnly property, to allow end-user to configure state of connection (read-only/writable) when failed over.
Backported “change user” and “reset server state” functionality from 3.1 branch, to allow clients of MysqlConnectionPoolDataSource to reset server state on getConnection() on a pooled connection.
Don't escape SJIS/GBK/BIG5 when using MySQL-4.1 or newer.
Allow url parameter for MysqlDataSource and MysqlConnectionPool DataSource so that passing of other properties is possible from inside appservers.
Map duplicate key and foreign key errors to SQLState of 23000.
Backport documentation tooling from 3.1 branch.
Return creating statement for ResultSets created by getGeneratedKeys(). (Bug #2957)
Allow java.util.Date to be sent in as parameter to PreparedStatement.setObject(), converting it to a Timestamp to maintain full precision. (Bug #103).
Don't truncate BLOB or CLOB values when using setBytes() and/or setBinary/CharacterStream(). (Bug #2670).
Dynamically configure character set mappings for field-level character sets on MySQL-4.1.0 and newer using SHOW COLLATION when connecting.
Map binary character set to US-ASCII to support DATETIME charset recognition for servers >= 4.1.2.
Use SET character_set_results during initialization to allow any charset to be returned to the driver for result sets.
Use charsetnr returned during connect to encode queries before issuing SET NAMES on MySQL >= 4.1.0.
Add helper methods to ResultSetMetaData (getColumnCharacterEncoding() and getColumnCharacterSet()) to allow end-users to see what charset the driver thinks it should be using for the column.
Only set character_set_results for MySQL >= 4.1.0.
StringUtils.escapeSJISByteStream() not covering all eastern double-byte charsets correctly. (Bug #3511)
Renamed StringUtils.escapeSJISByteStream() to more appropriate escapeEasternUnicodeByteStream().
Not specifying database in URL caused MalformedURL exception. (Bug #3554)
Auto-convert MySQL encoding names to Java encoding names if used for characterEncoding property.
Added encoding names that are recognized on some JVMs to fix case where they were reverse-mapped to MySQL encoding names incorrectly.
Use junit.textui.TestRunner for all unit tests (to allow them to be run from the command line outside of Ant or Eclipse).
UpdatableResultSet not picking up default values for moveToInsertRow(). (Bug #3557)
Inconsistent reporting of data type. The server still doesn't return all types for *BLOBs *TEXT correctly, so the driver won't return those correctly. (Bug #3570)
DBMD.getSQLStateType() returns incorrect value. (Bug #3520)
Fixed regression in PreparedStatement.setString() and eastern character encodings.
Made StringRegressionTest 4.1-unicode aware.

23.3.6.26. Changes in MySQL Connector/J 3.0.11-stable (19 February 2004)

Trigger a SET NAMES utf8 when encoding is forced to utf8 or utf-8 via the characterEncoding property. Previously, only the Java-style encoding name of utf-8 would trigger this.
AutoReconnect time was growing faster than exponentially. (Bug #2447)
Fixed failover always going to last host in list. (Bug #2578)
Added useUnbufferedInput parameter, and now use it by default (due to JVM issue http://developer.java.sun.com/developer/bugParade/bugs/4401235.html)
Detect on/off or 1, 2, 3 form of lower_case_table_names value on server.
Return java.lang.Integer for TINYINT and SMALLINT types from ResultSetMetaData.getColumnClassName(). (Bug #2852)
Return java.lang.Double for FLOAT type from ResultSetMetaData.getColumnClassName(). (Bug #2855)
Return [B instead of java.lang.Object for BINARY, VARBINARY and LONGVARBINARY types from ResultSetMetaData.getColumnClassName() (JDBC compliance).
Issue connection events on all instances created from a ConnectionPoolDataSource.

23.3.6.27. Changes in MySQL Connector/J 3.0.10-stable (13 January 2004)

Don't count quoted IDs when inside a 'string' in PreparedStatement parsing. (Bug #1511)
“Friendlier” exception message for PacketTooLargeException. (Bug #1534)
Backported fix for aliased tables and UpdatableResultSets in checkUpdatability() method from 3.1 branch.
Fix for ArrayIndexOutOfBounds exception when using Statement.setMaxRows(). (Bug #1695)
Barge blobs and split packets not being read correctly. (Bug #1576)
Fixed regression of Statement.getGeneratedKeys() and REPLACE statements.
Subsequent call to ResultSet.updateFoo() causes NPE if result set is not updatable. (Bug #1630)
Fix for 4.1.1-style authentication with no password.
Foreign Keys column sequence is not consistent in DatabaseMetaData.getImported/Exported/CrossReference(). (Bug #1731)
DatabaseMetaData.getSystemFunction() returning bad function VResultsSion. (Bug #1775)
Cross-database updatable result sets are not checked for updatability correctly. (Bug #1592)
DatabaseMetaData.getColumns() should return Types.LONGVARCHAR for MySQL LONGTEXT type.
ResultSet.getObject() on TINYINT and SMALLINT columns should return Java type Integer. (Bug #1913)
Added alwaysClearStream connection property, which causes the driver to always empty any remaining data on the input stream before each query.
Added more descriptive error message Server Configuration Denies Access to DataSource, as well as retrieval of message from server.
Autoreconnect code didn't set catalog upon reconnect if it had been changed.
Implement ResultSet.updateClob().
ResultSetMetaData.isCaseSensitive() returned wrong value for CHAR/VARCHAR columns.
Connection property maxRows not honored. (Bug #1933)
Statements being created too many times in DBMD.extractForeignKeyFromCreateTable(). (Bug #1925)
Support escape sequence {fn convert ... }. (Bug #1914)
ArrayIndexOutOfBounds when parameter number == number of parameters + 1. (Bug #1958)
ResultSet.findColumn() should use first matching column name when there are duplicate column names in SELECT query (JDBC-compliance). (Bug #2006)
Removed static synchronization bottleneck from PreparedStatement.setTimestamp().
Removed static synchronization bottleneck from instance factory method of SingleByteCharsetConverter.
Enable caching of the parsing stage of prepared statements via the cachePrepStmts, prepStmtCacheSize, and prepStmtCacheSqlLimit properties (disabled by default).
Speed up parsing of PreparedStatements, try to use one-pass whenever possible.
Fixed security exception when used in Applets (applets can't read the system property file.encoding which is needed for LOAD DATA LOCAL INFILE).
Use constants for SQLStates.
Map charset ko18_ru to ko18r when connected to MySQL-4.1.0 or newer.
Ensure that Buffer.writeString() saves room for the \0.
Fixed exception Unknown character set 'danish' on connect with JDK-1.4.0
Fixed mappings in SQLError to report deadlocks with SQLStates of 41000.
maxRows property would affect internal statements, so check it for all statement creation internal to the driver, and set to 0 when it is not.

23.3.6.28. Changes in MySQL Connector/J 3.0.9-stable (07 October 2003)

Faster date handling code in ResultSet and PreparedStatement (no longer uses Date methods that synchronize on static calendars).
Fixed test for end of buffer in Buffer.readString().
Fixed ResultSet.previous() behavior to move current position to before result set when on first row of result set. (Bug #496)
Fixed Statement and PreparedStatement issuing bogus queries when setMaxRows() had been used and a LIMIT clause was present in the query.
refreshRow didn't work when primary key values contained values that needed to be escaped (they ended up being doubly escaped). (Bug #661)
Support InnoDB contraint names when extracting foreign key information in DatabaseMetaData (implementing ideas from Parwinder Sekhon). (Bug #517, Bug #664)
Backported 4.1 protocol changes from 3.1 branch (server-side SQL states, new field information, larger client capability flags, connect-with-database, and so forth).
Fix UpdatableResultSet to return values for getXXX() when on insert row. (Bug #675)
The insertRow in an UpdatableResultSet is now loaded with the default column values when moveToInsertRow() is called. (Bug #688)
DatabaseMetaData.getColumns() wasn't returning NULL for default values that are specified as NULL.
Change default statement type/concurrency to TYPE_FORWARD_ONLY and CONCUR_READ_ONLY (spec compliance).
Don't try and reset isolation level on reconnect if MySQL doesn't support them.
Don't wrap SQLExceptions in RowDataDynamic.
Don't change timestamp TZ twice if useTimezone==true. (Bug #774)
Fixed regression in large split-packet handling. (Bug #848)
Better diagnostic error messages in exceptions for “streaming” result sets.
Issue exception on ResultSet.getXXX() on empty result set (wasn't caught in some cases).
Don't hide messages from exceptions thrown in I/O layers.
Don't fire connection closed events when closing pooled connections, or on PooledConnection.getConnection() with already open connections. (Bug #884)
Clip +/- INF (to smallest and largest representative values for the type in MySQL) and NaN (to 0) for setDouble/setFloat(), and issue a warning on the statement when the server does not support +/- INF or NaN.
Double-escaping of '\' when charset is SJIS or GBK and '\' appears in non-escaped input. (Bug #879)
When emptying input stream of unused rows for “streaming” result sets, have the current thread yield() every 100 rows in order to not monopolize CPU time.
DatabaseMetaData.getColumns() getting confused about the keyword “set” in character columns. (Bug #1099)
Fixed deadlock issue with Statement.setMaxRows().
Fixed CLOB.truncate(). (Bug #1130)
Optimized CLOB.setChracterStream(). (Bug #1131)
Made databaseName, portNumber, and serverName optional parameters for MysqlDataSourceFactory. (Bug #1246)
ResultSet.get/setString mashing char 127. (Bug #1247)
Backported authentication changes for 4.1.1 and newer from 3.1 branch.
Added com.mysql.jdbc.util.BaseBugReport to help creation of testcases for bug reports.
Added property to “clobber” streaming results, by setting the clobberStreamingResults property to true (the default is false). This will cause a “streaming” ResultSet to be automatically closed, and any oustanding data still streaming from the server to be discarded if another query is executed before all the data has been read from the server.

23.3.6.29. Changes in MySQL Connector/J 3.0.8-stable (23 May 2003)

Allow bogus URLs in Driver.getPropertyInfo().
Return list of generated keys when using multi-value INSERTS with Statement.getGeneratedKeys().
Use JVM charset with filenames and LOAD DATA [LOCAL] INFILE.
Fix infinite loop with Connection.cleanup().
Changed Ant target compile-core to compile-driver, and made testsuite compilation a separate target.
Fixed result set not getting set for Statement.executeUpdate(), which affected getGeneratedKeys() and getUpdateCount() in some cases.
Unicode character 0xFFFF in a string would cause the driver to throw an ArrayOutOfBoundsException. (Bug #378).
Return correct number of generated keys when using REPLACE statements.
Fix problem detecting server character set in some cases.
Fix row data decoding error when using very large packets.
Optimized row data decoding.
Issue exception when operating on an already closed prepared statement.
Fixed SJIS encoding bug, thanks to Naoto Sato.
Optimized usage of EscapeProcessor.
Allow multiple calls to Statement.close().

23.3.6.30. Changes in MySQL Connector/J 3.0.7-stable (08 April 2003)

Fixed MysqlPooledConnection.close() calling wrong event type.
Fixed StringIndexOutOfBoundsException in PreparedStatement.setClob().
4.1 Column Metadata fixes.
Remove synchronization from Driver.connect() and Driver.acceptsUrl().
IOExceptions during a transaction now cause the Connection to be closed.
Fixed missing conversion for YEAR type in ResultSetMetaData.getColumnTypeName().
Don't pick up indexes that start with pri as primary keys for DBMD.getPrimaryKeys().
Throw SQLExceptions when trying to do operations on a forcefully closed Connection (that is, when a communication link failure occurs).
You can now toggle profiling on/off using Connection.setProfileSql(boolean).
Fixed charset issues with database metadata (charset was not getting set correctly).
Updatable ResultSets can now be created for aliased tables/columns when connected to MySQL-4.1 or newer.
Fixed LOAD DATA LOCAL INFILE bug when file > max_allowed_packet.
Fixed escaping of 0x5c ('\') character for GBK and Big5 charsets.
Fixed ResultSet.getTimestamp() when underlying field is of type DATE.
Ensure that packet size from alignPacketSize() does not exceed max_allowed_packet (JVM bug)
Don't reset Connection.isReadOnly() when autoReconnecting.

23.3.6.31. Changes in MySQL Connector/J 3.0.6-stable (18 February 2003)

Fixed ResultSetMetaData to return "" when catalog not known. Fixes NullPointerExceptions with Sun's CachedRowSet.
Fixed DBMD.getTypeInfo() and DBMD.getColumns() returning different value for precision in TEXT and BLOB types.
Allow ignoring of warning for “non transactional tables” during rollback (compliance/usability) by setting ignoreNonTxTables property to true.
Fixed SQLExceptions getting swallowed on initial connect.
Fixed Statement.setMaxRows() to stop sending LIMIT type queries when not needed (performance).
Clean up Statement query/method mismatch tests (that is, INSERT not allowed with .executeQuery()).
More checks added in ResultSet traversal method to catch when in closed state.
Fixed ResultSetMetaData.isWritable() to return correct value.
Add “window” of different NULL sorting behavior to DBMD.nullsAreSortedAtStart (4.0.2 to 4.0.10, true; otherwise, no).
Implemented Blob.setBytes(). You still need to pass the resultant Blob back into an updatable ResultSet or PreparedStatement to persist the changes, because MySQL does not support “locators”.
Backported 4.1 charset field info changes from Connector/J 3.1.

23.3.6.32. Changes in MySQL Connector/J 3.0.5-gamma (22 January 2003)

Fixed Buffer.fastSkipLenString() causing ArrayIndexOutOfBounds exceptions with some queries when unpacking fields.
Implemented an empty TypeMap for Connection.getTypeMap() so that some third-party apps work with MySQL (IBM WebSphere 5.0 Connection pool).
Added missing LONGTEXT type to DBMD.getColumns().
Retrieve TX_ISOLATION from database for Connection.getTransactionIsolation() when the MySQL version supports it, instead of an instance variable.
Quote table names in DatabaseMetaData.getColumns(), getPrimaryKeys(), getIndexInfo(), getBestRowIdentifier().
Greatly reduce memory required for setBinaryStream() in PreparedStatements.
Fixed ResultSet.isBeforeFirst() for empty result sets.
Added update options for foreign key metadata.

23.3.6.33. Changes in MySQL Connector/J 3.0.4-gamma (06 January 2003)

Added quoted identifiers to database names for Connection.setCatalog.
Added support for quoted identifiers in PreparedStatement parser.
Streamlined character conversion and byte[] handling in PreparedStatements for setByte().
Reduce memory footprint of PreparedStatements by sharing outbound packet with MysqlIO.
Added strictUpdates property to allow control of amount of checking for “correctness” of updatable result sets. Set this to false if you want faster updatable result sets and you know that you create them from SELECT statements on tables with primary keys and that you have selected all primary keys in your query.
Added support for 4.0.8-style large packets.
Fixed PreparedStatement.executeBatch() parameter overwriting.

23.3.6.34. Changes in MySQL Connector/J 3.0.3-dev (17 December 2002)

Changed charsToByte in SingleByteCharConverter to be non-static.
Changed SingleByteCharConverter to use lazy initialization of each converter.
Fixed charset handling in Fields.java.
Implemented Connection.nativeSQL().
More robust escape tokenizer: Recognize -- comments, and allow nested escape sequences (see testsuite.EscapeProcessingTest).
DBMD.getImported/ExportedKeys() now handles multiple foreign keys per table.
Fixed ResultSetMetaData.getPrecision() returning incorrect values for some floating-point types.
Fixed ResultSetMetaData.getColumnTypeName() returning BLOB for TEXT and TEXT for BLOB types.
Fixed Buffer.isLastDataPacket() for 4.1 and newer servers.
Added CLIENT_LONG_FLAG to be able to get more column flags (isAutoIncrement() being the most important).
Because of above, implemented ResultSetMetaData.isAutoIncrement() to use Field.isAutoIncrement().
Honor lower_case_table_names when enabled in the server when doing table name comparisons in DatabaseMetaData methods.
Some MySQL-4.1 protocol support (extended field info from selects).
Use non-aliased table/column names and database names to fullly qualify tables and columns in UpdatableResultSet (requires MySQL-4.1 or newer).
Allow user to alter behavior of Statement/ PreparedStatement.executeBatch() via continueBatchOnError property (defaults to true).
Check for connection closed in more Connection methods (createStatement, prepareStatement, setTransactionIsolation, setAutoCommit).
More robust implementation of updatable result sets. Checks that all primary keys of the table have been selected.
LOAD DATA LOCAL INFILE ... now works, if your server is configured to allow it. Can be turned off with the allowLoadLocalInfile property (see the README).
Substitute '?' for unknown character conversions in single-byte character sets instead of '\0'.
NamedPipeSocketFactory now works (only intended for Windows), see README for instructions.

23.3.6.35. Changes in MySQL Connector/J 3.0.2-dev (08 November 2002)

Fixed issue with updatable result sets and PreparedStatements not working.
Fixed ResultSet.setFetchDirection(FETCH_UNKNOWN).
Fixed issue when calling Statement.setFetchSize() when using arbitrary values.
Fixed incorrect conversion in ResultSet.getLong().
Implemented ResultSet.updateBlob().
Removed duplicate code from UpdatableResultSet (it can be inherited from ResultSet, the extra code for each method to handle updatability I thought might someday be necessary has not been needed).
Fixed UnsupportedEncodingException thrown when “forcing” a character encoding via properties.
Fixed various non-ASCII character encoding issues.
Added driver property useHostsInPrivileges. Defaults to true. Affects whether or not @hostname will be used in DBMD.getColumn/TablePrivileges.
All DBMD result set columns describing schemas now return NULL to be more compliant with the behavior of other JDBC drivers for other database systems (MySQL does not support schemas).
Added SSL support. See README for information on how to use it.
Properly restore connection properties when autoReconnecting or failing-over, including autoCommit state, and isolation level.
Use SHOW CREATE TABLE when possible for determining foreign key information for DatabaseMetaData. Also allows cascade options for DELETE information to be returned.
Escape 0x5c character in strings for the SJIS charset.
Fixed start position off-by-1 error in Clob.getSubString().
Implemented Clob.truncate().
Implemented Clob.setString().
Implemented Clob.setAsciiStream().
Implemented Clob.setCharacterStream().
Added com.mysql.jdbc.MiniAdmin class, which allows you to send shutdown command to MySQL server. This is intended to be used when “embedding” Java and MySQL server together in an end-user application.
Added connectTimeout parameter that allows users of JDK-1.4 and newer to specify a maxium time to wait to establish a connection.
Failover and autoReconnect work only when the connection is in an autoCommit(false) state, in order to stay transaction-safe.
Added queriesBeforeRetryMaster property that specifies how many queries to issue when failed over before attempting to reconnect to the master (defaults to 50).
Fixed DBMD.supportsResultSetConcurrency() so that it returns true for ResultSet.TYPE_SCROLL_INSENSITIVE and ResultSet.CONCUR_READ_ONLY or ResultSet.CONCUR_UPDATABLE.
Fixed ResultSet.isLast() for empty result sets (should return false).
PreparedStatement now honors stream lengths in setBinary/Ascii/Character Stream() unless you set the connection property useStreamLengthsInPrepStmts to false.
Removed some not-needed temporary object creation by smarter use of Strings in EscapeProcessor, Connection and DatabaseMetaData classes.

23.3.6.36. Changes in MySQL Connector/J 3.0.1-dev (21 September 2002)

Fixed ResultSet.getRow() off-by-one bug.
Fixed RowDataStatic.getAt() off-by-one bug.
Added limited Clob functionality (ResultSet.getClob(), PreparedStatemtent.setClob(), PreparedStatement.setObject(Clob).
Added socketTimeout parameter to URL.
Connection.isClosed() no longer “pings” the server.
Connection.close() issues rollback() when getAutoCommit() is false.
Added paranoid parameter, which sanitizes error messages by removing “sensitive” information from them (such as hostnames, ports, or usernames), as well as clearing “sensitive” data structures when possible.
Fixed ResultSetMetaData.isSigned() for TINYINT and BIGINT.
Charsets now automatically detected. Optimized code for single-byte character set conversion.
Implemented ResultSet.getCharacterStream().
Added LOCAL TEMPORARY to table types in DatabaseMetaData.getTableTypes().
Massive code clean-up to follow Java coding conventions (the time had come).

23.3.6.37. Changes in MySQL Connector/J 3.0.0-dev (31 July 2002)

!!! LICENSE CHANGE !!! The driver is now GPL. If you need non-GPL licenses, please contact me <mark@mysql.com>.
JDBC-3.0 functionality including Statement/PreparedStatement.getGeneratedKeys() and ResultSet.getURL().
Performance enchancements: Driver is now 50–100% faster in most situations, and creates fewer temporary objects.
Repackaging: New driver name is com.mysql.jdbc.Driver, old name still works, though (the driver is now provided by MySQL-AB).
Better checking for closed connections in Statement and PreparedStatement.
Support for streaming (row-by-row) result sets (see README) Thanks to Doron.
Support for large packets (new addition to MySQL-4.0 protocol), see README for more information.
JDBC Compliance: Passes all tests besides stored procedure tests.
Fix and sort primary key names in DBMetaData (SF bugs 582086 and 582086).
Float types now reported as java.sql.Types.FLOAT (SF bug 579573).
ResultSet.getTimestamp() now works for DATE types (SF bug 559134).
ResultSet.getDate/Time/Timestamp now recognizes all forms of invalid values that have been set to all zeros by MySQL (SF bug 586058).
Testsuite now uses Junit (which you can get from http://www.junit.org.
The driver now only works with JDK-1.2 or newer.
Added multi-host failover support (see README).
General source-code cleanup.
Overall speed improvements via controlling transient object creation in MysqlIO class when reading packets.
Performance improvements in string handling and field metadata creation (lazily instantiated) contributed by Alex Twisleton-Wykeham-Fiennes.

23.3.6.38. Changes in MySQL Connector/J 2.0.14 (16 May 2002)

More code cleanup.
PreparedStatement now releases resources on .close(). (SF bug 553268)
Quoted identifiers not used if server version does not support them. Also, if server started with --ansi or --sql-mode=ANSI_QUOTES, ‘"’ will be used as an identifier quote character, otherwise ‘'’ will be used.
ResultSet.getDouble() now uses code built into JDK to be more precise (but slower).
LogicalHandle.isClosed() calls through to physical connection.
Added SQL profiling (to STDERR). Set profileSql=true in your JDBC URL. See README for more information.
Fixed typo for relaxAutoCommit parameter.

23.3.6.39. Changes in MySQL Connector/J 2.0.13 (24 April 2002)

More code cleanup.
Fixed unicode chars being read incorrectly. (SF bug 541088)
Faster blob escaping for PrepStmt.
Added set/getPortNumber() to DataSource(s). (SF bug 548167)
Added setURL() to MySQLXADataSource. (SF bug 546019)
PreparedStatement.toString() fixed. (SF bug 534026)
ResultSetMetaData.getColumnClassName() now implemented.
Rudimentary version of Statement.getGeneratedKeys() from JDBC-3.0 now implemented (you need to be using JDK-1.4 for this to work, I believe).
DBMetaData.getIndexInfo() - bad PAGES fixed. (SF BUG 542201)

23.3.6.40. Changes in MySQL Connector/J 2.0.12 (07 April 2002)

General code cleanup.
Added getIdleFor() method to Connection and MysqlLogicalHandle.
Relaxed synchronization in all classes, should fix 520615 and 520393.
Added getTable/ColumnPrivileges() to DBMD (fixes 484502).
Added new types to getTypeInfo(), fixed existing types thanks to Al Davis and Kid Kalanon.
Added support for BIT types (51870) to PreparedStatement.
Fixed getRow() bug (527165) in ResultSet.
Fixes for ResultSet updatability in PreparedStatement.
Fixed time zone off-by-1-hour bug in PreparedStatement (538286, 528785).
ResultSet: Fixed updatability (values being set to null if not updated).
DataSources - fixed setUrl bug (511614, 525565), wrong datasource class name (532816, 528767).
Added identifier quoting to all DatabaseMetaData methods that need them (should fix 518108).
Added support for YEAR type (533556).
ResultSet.insertRow() should now detect auto_increment fields in most cases and use that value in the new row. This detection will not work in multi-valued keys, however, due to the fact that the MySQL protocol does not return this information.
ResultSet.refreshRow() implemented.
Fixed testsuite.Traversal afterLast() bug, thanks to Igor Lastric.

23.3.6.41. Changes in MySQL Connector/J 2.0.11 (27 January 2002)

Fixed missing DELETE_RULE value in DBMD.getImported/ExportedKeys() and getCrossReference().
Full synchronization of Statement.java.
More changes to fix Unexpected end of input stream errors when reading BLOB values. This should be the last fix.

23.3.6.42. Changes in MySQL Connector/J 2.0.10 (24 January 2002)

Fixed spurious Unexpected end of input stream errors in MysqlIO (bug 507456).
Fixed null-pointer-exceptions when using MysqlConnectionPoolDataSource with Websphere 4 (bug 505839).

23.3.6.43. Changes in MySQL Connector/J 2.0.9 (13 January 2002)

Ant build was corrupting included jar files, fixed (bug 487669).
Fixed extra memory allocation in MysqlIO.readPacket() (bug 488663).
Implementation of DatabaseMetaData.getExported/ImportedKeys() and getCrossReference().
Full synchronization on methods modifying instance and class-shared references, driver should be entirely thread-safe now (please let me know if you have problems).
DataSource implementations moved to org.gjt.mm.mysql.jdbc2.optional package, and (initial) implementations of PooledConnectionDataSource and XADataSource are in place (thanks to Todd Wolff for the implementation and testing of PooledConnectionDataSource with IBM WebSphere 4).
Added detection of network connection being closed when reading packets (thanks to Todd Lizambri).
Fixed quoting error with escape processor (bug 486265).
Report batch update support through DatabaseMetaData (bug 495101).
Fixed off-by-one-hour error in PreparedStatement.setTimestamp() (bug 491577).
Removed concatenation support from driver (the || operator), as older versions of VisualAge seem to be the only thing that use it, and it conflicts with the logical || operator. You will need to start mysqld with the --ansi flag to use the || operator as concatenation (bug 491680).
Fixed casting bug in PreparedStatement (bug 488663).

23.3.6.44. Changes in MySQL Connector/J 2.0.8 (25 November 2001)

Batch updates now supported (thanks to some inspiration from Daniel Rall).
XADataSource/ConnectionPoolDataSource code (experimental)
PreparedStatement.setAnyNumericType() now handles positive exponents correctly (adds + so MySQL can understand it).
DatabaseMetaData.getPrimaryKeys() and getBestRowIdentifier() are now more robust in identifying primary keys (matches regardless of case or abbreviation/full spelling of Primary Key in Key_type column).

23.3.6.45. Changes in MySQL Connector/J 2.0.7 (24 October 2001)

PreparedStatement.setCharacterStream() now implemented
Fixed dangling socket problem when in high availability (autoReconnect=true) mode, and finalizer for Connection will close any dangling sockets on GC.
Fixed ResultSetMetaData.getPrecision() returning one less than actual on newer versions of MySQL.
ResultSet.getBlob() now returns null if column value was null.
Character sets read from database if useUnicode=true and characterEncoding is not set. (thanks to Dmitry Vereshchagin)
Initial transaction isolation level read from database (if avaialable). (thanks to Dmitry Vereshchagin)
Fixed DatabaseMetaData.supportsTransactions(), and supportsTransactionIsolationLevel() and getTypeInfo() SQL_DATETIME_SUB and SQL_DATA_TYPE fields not being readable.
Fixed PreparedStatement generating SQL that would end up with syntax errors for some queries.
Fixed ResultSet.isAfterLast() always returning false.
Fixed time zone issue in PreparedStatement.setTimestamp(). (thanks to Erik Olofsson)
Captialize type names when captializeTypeNames=true is passed in URL or properties (for WebObjects. (thanks to Anjo Krank)
Updatable result sets now correctly handle NULL values in fields.
PreparedStatement.setDouble() now uses full-precision doubles (reverting a fix made earlier to truncate them).
PreparedStatement.setBoolean() will use 1/0 for values if your MySQL version is 3.21.23 or higher.

23.3.6.46. Changes in MySQL Connector/J 2.0.6 (16 June 2001)

Fixed PreparedStatement parameter checking.
Fixed case-sensitive column names in ResultSet.java.

23.3.6.47. Changes in MySQL Connector/J 2.0.5 (13 June 2001)

Fixed ResultSet.getBlob() ArrayIndex out-of-bounds.
Fixed ResultSetMetaData.getColumnTypeName for TEXT/BLOB.
Fixed ArrayIndexOutOfBounds when sending large BLOB queries. (Max size packet was not being set)
Added ISOLATION level support to Connection.setIsolationLevel()
Fixed NPE on PreparedStatement.executeUpdate() when all columns have not been set.
Fixed data parsing of TIMESTAMP values with 2-digit years.
Added Byte to PreparedStatement.setObject().
ResultSet.getBoolean() now recognizes -1 as true.
ResultSet has +/-Inf/inf support.
ResultSet.insertRow() works now, even if not all columns are set (they will be set to NULL).
DataBaseMetaData.getCrossReference() no longer ArrayIndexOOB.
getObject() on ResultSet correctly does TINYINT->Byte and SMALLINT->Short.

23.3.6.48. Changes in MySQL Connector/J 2.0.3 (03 December 2000)

Implemented getBigDecimal() without scale component for JDBC2.
Fixed composite key problem with updatable result sets.
Added detection of -/+INF for doubles.
Faster ASCII string operations.
Fixed incorrect detection of MAX_ALLOWED_PACKET, so sending large blobs should work now.
Fixed off-by-one error in java.sql.Blob implementation code.
Added ultraDevHack URL parameter, set to true to allow (broken) Macromedia UltraDev to use the driver.

23.3.6.49. Changes in MySQL Connector/J 2.0.1 (06 April 2000)

Fixed RSMD.isWritable() returning wrong value. Thanks to Moritz Maass.
Cleaned up exception handling when driver connects.
Columns that are of type TEXT now return as Strings when you use getObject().
DatabaseMetaData.getPrimaryKeys() now works correctly with respect to key_seq. Thanks to Brian Slesinsky.
No escape processing is done on PreparedStatements anymore per JDBC spec.
Fixed many JDBC-2.0 traversal, positioning bugs, especially with respect to empty result sets. Thanks to Ron Smits, Nick Brook, Cessar Garcia and Carlos Martinez.
Fixed some issues with updatability support in ResultSet when using multiple primary keys.

23.3.6.50. Changes in MySQL Connector/J 2.0.0pre5 (21 February 2000)

Fixed Bad Handshake problem.

23.3.6.51. Changes in MySQL Connector/J 2.0.0pre4 (10 January 2000)

Fixes to ResultSet for insertRow() - Thanks to Cesar Garcia
Fix to Driver to recognize JDBC-2.0 by loading a JDBC-2.0 class, instead of relying on JDK version numbers. Thanks to John Baker.
Fixed ResultSet to return correct row numbers
Statement.getUpdateCount() now returns rows matched, instead of rows actually updated, which is more SQL-92 like.

10-29-99

Statement/PreparedStatement.getMoreResults() bug fixed. Thanks to Noel J. Bergman.
Added Short as a type to PreparedStatement.setObject(). Thanks to Jeff Crowder
Driver now automagically configures maximum/preferred packet sizes by querying server.
Autoreconnect code uses fast ping command if server supports it.
Fixed various bugs with respect to packet sizing when reading from the server and when alloc'ing to write to the server.

23.3.6.52. Changes in MySQL Connector/J 2.0.0pre (17 August 1999)

Now compiles under JDK-1.2. The driver supports both JDK-1.1 and JDK-1.2 at the same time through a core set of classes. The driver will load the appropriate interface classes at runtime by figuring out which JVM version you are using.
Fixes for result sets with all nulls in the first row. (Pointed out by Tim Endres)
Fixes to column numbers in SQLExceptions in ResultSet (Thanks to Blas Rodriguez Somoza)
The database no longer needs to specified to connect. (Thanks to Christian Motschke)

23.3.6.53. Changes in MySQL Connector/J 1.2b (04 July 1999)

Better Documentation (in progress), in doc/mm.doc/book1.html
DBMD now allows null for a column name pattern (not in spec), which it changes to '%'.
DBMD now has correct types/lengths for getXXX().
ResultSet.getDate(), getTime(), and getTimestamp() fixes. (contributed by Alan Wilken)
EscapeProcessor now handles \{ \} and { or } inside quotes correctly. (thanks to Alik for some ideas on how to fix it)
Fixes to properties handling in Connection. (contributed by Juho Tikkala)
ResultSet.getObject() now returns null for NULL columns in the table, rather than bombing out. (thanks to Ben Grosman)
ResultSet.getObject() now returns Strings for types from MySQL that it doesn't know about. (Suggested by Chris Perdue)
Removed DataInput/Output streams, not needed, 1/2 number of method calls per IO operation.
Use default character encoding if one is not specified. This is a work-around for broken JVMs, because according to spec, EVERY JVM must support "ISO8859_1", but they don't.
Fixed Connection to use the platform character encoding instead of "ISO8859_1" if one isn't explicitly set. This fixes problems people were having loading the character- converter classes that didn't always exist (JVM bug). (thanks to Fritz Elfert for pointing out this problem)
Changed MysqlIO to re-use packets where possible to reduce memory usage.
Fixed escape-processor bugs pertaining to {} inside quotes.

23.3.6.54. Changes in MySQL Connector/J 1.2a (14 April 1999)

Fixed character-set support for non-Javasoft JVMs (thanks to many people for pointing it out)
Fixed ResultSet.getBoolean() to recognize 'y' & 'n' as well as '1' & '0' as boolean flags. (thanks to Tim Pizey)
Fixed ResultSet.getTimestamp() to give better performance. (thanks to Richard Swift)
Fixed getByte() for numeric types. (thanks to Ray Bellis)
Fixed DatabaseMetaData.getTypeInfo() for DATE type. (thanks to Paul Johnston)
Fixed EscapeProcessor for "fn" calls. (thanks to Piyush Shah at locomotive.org)
Fixed EscapeProcessor to not do extraneous work if there are no escape codes. (thanks to Ryan Gustafson)
Fixed Driver to parse URLs of the form "jdbc:mysql://host:port" (thanks to Richard Lobb)

23.3.6.55. Changes in MySQL Connector/J 1.1i (24 March 1999)

Fixed Timestamps for PreparedStatements
Fixed null pointer exceptions in RSMD and RS
Re-compiled with jikes for valid class files (thanks ms!)

23.3.6.56. Changes in MySQL Connector/J 1.1h (08 March 1999)

Fixed escape processor to deal with unmatched { and } (thanks to Craig Coles)
Fixed escape processor to create more portable (between DATETIME and TIMESTAMP types) representations so that it will work with BETWEEN clauses. (thanks to Craig Longman)
MysqlIO.quit() now closes the socket connection. Before, after many failed connections some OS's would run out of file descriptors. (thanks to Michael Brinkman)
Fixed NullPointerException in Driver.getPropertyInfo. (thanks to Dave Potts)
Fixes to MysqlDefs to allow all *text fields to be retrieved as Strings. (thanks to Chris at Leverage)
Fixed setDouble in PreparedStatement for large numbers to avoid sending scientific notation to the database. (thanks to J.S. Ferguson)
Fixed getScale() and getPrecision() in RSMD. (contrib'd by James Klicman)
Fixed getObject() when field was DECIMAL or NUMERIC (thanks to Bert Hobbs)
DBMD.getTables() bombed when passed a null table-name pattern. Fixed. (thanks to Richard Lobb)
Added check for "client not authorized" errors during connect. (thanks to Hannes Wallnoefer)

23.3.6.57. Changes in MySQL Connector/J 1.1g (19 February 1999)

Result set rows are now byte arrays. Blobs and Unicode work bidriectonally now. The useUnicode and encoding options are implemented now.
Fixes to PreparedStatement to send binary set by setXXXStream to be sent untouched to the MySQL server.
Fixes to getDriverPropertyInfo().

23.3.6.58. Changes in MySQL Connector/J 1.1f (31 December 1998)

Changed all ResultSet fields to Strings, this should allow Unicode to work, but your JVM must be able to convert between the character sets. This should also make reading data from the server be a bit quicker, because there is now no conversion from StringBuffer to String.
Changed PreparedStatement.streamToString() to be more efficient (code from Uwe Schaefer).
URL parsing is more robust (throws SQL exceptions on errors rather than NullPointerExceptions)
PreparedStatement now can convert Strings to Time/Date values via setObject() (code from Robert Currey).
IO no longer hangs in Buffer.readInt(), that bug was introduced in 1.1d when changing to all byte-arrays for result sets. (Pointed out by Samo Login)

23.3.6.59. Changes in MySQL Connector/J 1.1b (03 November 1998)

Fixes to DatabaseMetaData to allow both IBM VA and J-Builder to work. Let me know how it goes. (thanks to Jac Kersing)
Fix to ResultSet.getBoolean() for NULL strings (thanks to Barry Lagerweij)
Beginning of code cleanup, and formatting. Getting ready to branch this off to a parallel JDBC-2.0 source tree.
Added "final" modifier to critical sections in MysqlIO and Buffer to allow compiler to inline methods for speed.

9-29-98

If object references passed to setXXX() in PreparedStatement are null, setNull() is automatically called for you. (Thanks for the suggestion goes to Erik Ostrom)
setObject() in PreparedStatement will now attempt to write a serialized representation of the object to the database for objects of Types.OTHER and objects of unknown type.
Util now has a static method readObject() which given a ResultSet and a column index will re-instantiate an object serialized in the above manner.

23.3.6.60. Changes in MySQL Connector/J 1.1 (02 September 1998)

Got rid of "ugly hack" in MysqlIO.nextRow(). Rather than catch an exception, Buffer.isLastDataPacket() was fixed.
Connection.getCatalog() and Connection.setCatalog() should work now.
Statement.setMaxRows() works, as well as setting by property maxRows. Statement.setMaxRows() overrides maxRows set via properties or url parameters.
Automatic re-connection is available. Because it has to "ping" the database before each query, it is turned off by default. To use it, pass in "autoReconnect=true" in the connection URL. You may also change the number of reconnect tries, and the initial timeout value via "maxReconnects=n" (default 3) and "initialTimeout=n" (seconds, default 2) parameters. The timeout is an exponential backoff type of timeout; for example, if you have initial timeout of 2 seconds, and maxReconnects of 3, then the driver will timeout 2 seconds, 4 seconds, then 16 seconds between each re-connection attempt.

23.3.6.61. Changes in MySQL Connector/J 1.0 (24 August 1998)

Fixed handling of blob data in Buffer.java
Fixed bug with authentication packet being sized too small.
The JDBC Driver is now under the LPGL

8-14-98

Fixed Buffer.readLenString() to correctly read data for BLOBS.
Fixed PreparedStatement.stringToStream to correctly read data for BLOBS.
Fixed PreparedStatement.setDate() to not add a day. (above fixes thanks to Vincent Partington)
Added URL parameter parsing (?user=... and so forth).

23.3.6.62. Changes in MySQL Connector/J 0.9d (04 August 1998)

Big news! New package name. Tim Endres from ICE Engineering is starting a new source tree for GNU GPL'd Java software. He's graciously given me the org.gjt.mm package directory to use, so now the driver is in the org.gjt.mm.mysql package scheme. I'm "legal" now. Look for more information on Tim's project soon.
Now using dynamically sized packets to reduce memory usage when sending commands to the DB.
Small fixes to getTypeInfo() for parameters, and so forth.
DatabaseMetaData is now fully implemented. Let me know if these drivers work with the various IDEs out there. I've heard that they're working with JBuilder right now.
Added JavaDoc documentation to the package.
Package now available in .zip or .tar.gz.

23.3.6.63. Changes in MySQL Connector/J 0.9 (28 July 1998)

Implemented getTypeInfo(). Connection.rollback() now throws an SQLException per the JDBC spec.
Added PreparedStatement that supports all JDBC API methods for PreparedStatement including InputStreams. Please check this out and let me know if anything is broken.
Fixed a bug in ResultSet that would break some queries that only returned 1 row.
Fixed bugs in DatabaseMetaData.getTables(), DatabaseMetaData.getColumns() and DatabaseMetaData.getCatalogs().
Added functionality to Statement that allows executeUpdate() to store values for IDs that are automatically generated for AUTO_INCREMENT fields. Basically, after an executeUpdate(), look at the SQLWarnings for warnings like "LAST_INSERTED_ID = 'some number', COMMAND = 'your SQL query'". If you are using AUTO_INCREMENT fields in your tables and are executing a lot of executeUpdate()s on one Statement, be sure to clearWarnings() every so often to save memory.

23.3.6.64. Changes in MySQL Connector/J 0.8 (06 July 1998)

Split MysqlIO and Buffer to separate classes. Some ClassLoaders gave an IllegalAccess error for some fields in those two classes. Now mm.mysql works in applets and all classloaders. Thanks to Joe Ennis <jce@mail.boone.com> for pointing out the problem and working on a fix with me.

23.3.6.65. Changes in MySQL Connector/J 0.7 (01 July 1998)

Fixed DatabaseMetadata problems in getColumns() and bug in switch statement in the Field constructor. Thanks to Costin Manolache <costin@tdiinc.com> for pointing these out.

23.3.6.66. Changes in MySQL Connector/J 0.6 (21 May 1998)

Incorporated efficiency changes from Richard Swift <Richard.Swift@kanatek.ca> in MysqlIO.java and ResultSet.java:
We're now 15% faster than gwe's driver.
Started working on DatabaseMetaData.
The following methods are implemented:
- getTables()
- getTableTypes()
- getColumns
- getCatalogs()