org.apache.commons.dbcp

Database Connection Pool API.

Q: How do I use the DBCP package?

A: There are two primary ways to access the DBCP pool, as a {@link java.sql.Driver Driver}, or as a {@link javax.sql.DataSource DataSource}. You'll want to create an instance of {@link org.apache.commons.dbcp.PoolingDriver} or {@link org.apache.commons.dbcp.PoolingDataSource}. When using one of these interfaces, you can just use your JDBC objects the way you normally would. Closing a {@link java.sql.Connection} will simply return it to its pool.

Q: But {@link org.apache.commons.dbcp.PoolingDriver PoolingDriver} and {@link org.apache.commons.dbcp.PoolingDataSource PoolingDataSource} both expect an {@link org.apache.commons.pool.ObjectPool ObjectPool} as an input. Where do I get one of those?

A: The {@link org.apache.commons.pool.ObjectPool ObjectPool} interface is defined in the {@link org.apache.commons.pool} package (Commons-Pool). The {@link org.apache.commons.pool.impl} package has a couple of implementations, and you can always create your own.

Q: Ok, I've found an {@link org.apache.commons.pool.ObjectPool ObjectPool} implementation that I think suits my connection pooling needs. But it wants a {@link org.apache.commons.pool.PoolableObjectFactory PoolableObjectFactory}. What should I use for that?

A: The DBCP package provides a class for this purpose. It's called {@link org.apache.commons.dbcp.PoolableConnectionFactory}. It implements the factory and lifecycle methods of {@link org.apache.commons.pool.PoolableObjectFactory} for {@link java.sql.Connection}s. But it doesn't create the actual database {@link java.sql.Connection}s itself, if uses a {@link org.apache.commons.dbcp.ConnectionFactory} for that. The {@link org.apache.commons.dbcp.PoolableConnectionFactory} will take {@link java.sql.Connection}s created by the {@link org.apache.commons.dbcp.ConnectionFactory} and wrap them with classes that implement the pooling behaviour.

Several implementations of {@link org.apache.commons.dbcp.ConnectionFactory} are provided--one that uses {@link java.sql.DriverManager} to create connections ({@link org.apache.commons.dbcp.DriverManagerConnectionFactory}), one that uses a {@link java.sql.Driver} to create connections ({@link org.apache.commons.dbcp.DriverConnectionFactory}), one that uses a {@link javax.sql.DataSource} to create connections ({@link org.apache.commons.dbcp.DataSourceConnectionFactory}).

Q: I think I'm starting to get it, but can you walk me though it again?

A: Sure. Let's assume you want to create a {@link javax.sql.DataSource} that pools {@link java.sql.Connection}s. Let's also assume that that those pooled {@link java.sql.Connection}s should be obtained from the {@link java.sql.DriverManager}. You'll want to create a {@link org.apache.commons.dbcp.PoolingDataSource}.

The {@link org.apache.commons.dbcp.PoolingDataSource} uses an underlying {@link org.apache.commons.pool.ObjectPool} to create and store its {@link java.sql.Connection}.

To create a {@link org.apache.commons.pool.ObjectPool}, you'll need a {@link org.apache.commons.pool.PoolableObjectFactory} that creates the actual {@link java.sql.Connection}s. That's what {@link org.apache.commons.dbcp.PoolableConnectionFactory} is for.

To create the {@link org.apache.commons.dbcp.PoolableConnectionFactory}, you'll need at least two things:

1. A {@link org.apache.commons.dbcp.ConnectionFactory} from which the actual database {@link java.sql.Connection}s will be obtained.
2. An empty and factory-less {@link org.apache.commons.pool.ObjectPool} in which the {@link java.sql.Connection}s will be stored.
   When you pass an {@link org.apache.commons.pool.ObjectPool} into the {@link org.apache.commons.dbcp.PoolableConnectionFactory}, it will automatically register itself as the {@link org.apache.commons.pool.PoolableObjectFactory} for that pool.

In code, that might look like this:

GenericObjectPool connectionPool = new GenericObjectPool(null);
ConnectionFactory connectionFactory = new DriverManagerConnectionFactory("jdbc:some:connect:string", "username", "password");
PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory(connectionFactory,connectionPool,null,null,false,true);
PoolingDataSource dataSource = new PoolingDataSource(connectionPool);

To create a {@link org.apache.commons.dbcp.PoolingDriver}, we do the same thing, except that instead of creating a {@link javax.sql.DataSource} on the last line, we create a {@link org.apache.commons.dbcp.PoolingDriver}, and register the connectionPool with it. E.g.,:

GenericObjectPool connectionPool = new GenericObjectPool(null);
ConnectionFactory connectionFactory = new DriverManagerConnectionFactory("jdbc:some:connect:string", "username", "password");
PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory(connectionFactory,connectionPool,null,null,false,true);
PoolingDriver driver = new PoolingDriver();
driver.registerPool("example",connectionPool);

Since the {@link org.apache.commons.dbcp.PoolingDriver} registers itself with the {@link java.sql.DriverManager} when it is created, now you can just go to the {@link java.sql.DriverManager} to create your {@link java.sql.Connection}s, like you normally would:

Connection conn = DriverManager.getConnection("jdbc:apache:commons:dbcp:example");

Q: Sounds complicated, is there an easier way?

A: If you're using the {@link org.apache.commons.dbcp.PoolingDriver}, you don't need to do this configuration in code. Instead, you can provide a JOCL document that describes the connection pool, and let the {@link org.apache.commons.dbcp.PoolingDriver} discover it at runtime.

Specifically, if the {@link org.apache.commons.dbcp.PoolingDriver} is asked for a {@link java.sql.Connection} from a pool that has not yet been registered, it will look for a named resource from which to read the pool's configuration, and create that pool.

For example, suppose you create a pool named "/eg" from a JOCL document. The "connect string" for this pool will be "jdbc:apache:commons:dbcp:/eg". To do this, you'll need a create a resource (just a file in your classpath) containing a JOCL description of the pool. Specifically, this JOCL document should define a {@link org.apache.commons.dbcp.PoolableConnectionFactory} from which the pool will be obtained. For example:

<object class="org.apache.commons.dbcp.PoolableConnectionFactory" xmlns="http://apache.org/xml/xmlns/jakarta/commons/jocl">
   <!-- the first argument is the ConnectionFactory -->
   <object class="org.apache.commons.dbcp.DriverManagerConnectionFactory">
      <string value="jdbc:some:connect:string"/>
      <object class="java.util.Properties" null="true"/>
   </object>
   <!-- the next argument is the ObjectPool -->
   <object class="org.apache.commons.pool.impl.GenericObjectPool">
      <object class="org.apache.commons.pool.PoolableObjectFactory" null="true"/>
      <int value="10"/> <!-- max active -->
      <byte value="1"/> <!-- when exhausted action, 0 = fail, 1 = block, 2 = grow -->
      <long value="2000"/> <!-- max wait -->
      <int value="10"/> <!-- max idle -->
      <boolean value="false"/> <!-- test on borrow -->
      <boolean value="false"/> <!-- test on return -->
      <long value="10000"/> <!-- time between eviction runs -->
      <int value="5"/> <!-- number of connections to test per eviction run -->
      <long value="5000"/> <!-- min evictable idle time -->
      <boolean value="true"/> <!-- test while idle -->
   </object>
   <!-- the next argument is the KeyedObjectPoolFactory -->
   <object class="org.apache.commons.pool.impl.StackKeyedObjectPoolFactory">
      <int value="5"/> <!-- max idle -->
   </object>
   <string value="SELECT COUNT(*) FROM DUAL"/> <!-- validation query -->
   <boolean value="false"/> <!-- default read only -->
   <boolean value="true"/> <!-- default auto commit -->
</object>

Simply save that file somewhere in your classpath as eg.jocl, and the {@link org.apache.commons.dbcp.PoolingDriver} will find it automatically. You need only register the {@link org.apache.commons.dbcp.PoolingDriver} (for example, using the jdbc.drivers property), and use the the {@link java.sql.DriverManager} to create your {@link java.sql.Connection}s, like you normally would:

Connection conn = DriverManager.getConnection("jdbc:apache:commons:dbcp:/eg");

(Note that without the leading slash, the pool must be located at org/apache/commons/dbcp/PoolingDriver/eg.jocl within your classpath. See {@link java.lang.Class#getResource} for details.)

An implementation of a Jakarta-Commons ObjectPool which tracks JDBC connections and can recover abandoned db connections. If logAbandoned=true, a stack trace will be printed for any abandoned db connections recovered.
author:
   Glenn L.

Basic implementation of javax.sql.DataSource that is configured via JavaBeans properties.

JNDI object factory that creates an instance of BasicDataSource that has been configured based on the RefAddr values of the specified Reference, which must match the names and data types of the BasicDataSource bean properties.

All of the methods from the CallableStatement interface simply call the corresponding method on the "delegate" provided in my constructor.

Extends AbandonedTrace to implement Statement tracking and logging of code which created the Statement.

All of the methods from the Connection interface simply check to see that the Connection is active, and call the corresponding method on the "delegate" provided in my constructor.

Extends AbandonedTrace to implement Connection tracking and logging of code which created the Connection.

All of the methods from the PreparedStatement interface simply check to see that the PreparedStatement is active, and call the corresponding method on the "delegate" provided in my constructor.

Extends AbandonedTrace to implement Statement tracking and logging of code which created the Statement.

All of the methods from the ResultSet interface simply call the corresponding method on the "delegate" provided in my constructor.

Extends AbandonedTrace to implement result set tracking and logging of code which created the ResultSet.

All of the methods from the Statement interface simply check to see that the Statement is active, and call the corresponding method on the "delegate" provided in my constructor.

Extends AbandonedTrace to implement Statement tracking and logging of code which created the Statement.

My PoolablePreparedStatement.close method returns me to my containing pool.

My PoolingConnection.prepareStatement methods, rather than creating a new PreparedStatement each time, may actually pull the PreparedStatement from a pool of unused statements. The PreparedStatement.close method of the returned PreparedStatement doesn't actually close the statement, but rather returns it to my pool.