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Database Connection Pool API.

Overview in Dialog Form

Q: How do I use the DBCP package?

 A: There are two primary ways to access the DBCP pool, as a Driver, or as a DataSource. You'll want to create an instance of PoolingDriver or PoolingDataSource. When using one of these interfaces, you can just use your JDBC objects the way you normally would. Closing a Connection will simply return it to its pool. 
 Q: But PoolingDriver and PoolingDataSource both expect an ObjectPool as an input. Where do I get one of those? 
 A: The ObjectPool interface is defined in Commons Pool. You can use one of the provided implementations such as GenericObjectPool, ProxiedObjectPool or SoftReferenceObjectPool or you can create your own. 
 Q: Ok, I've found an ObjectPool implementation that I think suits my connection pooling needs. But it wants a PooledObjectFactory. What should I use for that? 
 A: The DBCP package provides a class for this purpose. It's called PoolableConnectionFactory. It implements the factory and lifecycle methods of PooledObjectFactory for Connections. But it doesn't create the actual database Connections itself, it uses a ConnectionFactory for that. The PoolableConnectionFactory will take Connections created by the ConnectionFactory and wrap them with classes that implement the pooling behaviour. 
 Several implementations of ConnectionFactory are provided--one that uses DriverManager to create connections (DriverManagerConnectionFactory), one that uses a Driver to create connections (DriverConnectionFactory), one that uses a DataSource to create connections (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 DataSource that pools Connections. Let's also assume that those pooled Connections should be obtained from the DriverManager. You'll want to create a PoolingDataSource. 
 The PoolingDataSource uses an underlying ObjectPool to create and store its Connection. 
 To create a ObjectPool, you'll need a PooledObjectFactory that creates the actual Connections. That's what PoolableConnectionFactory is for. 
 To create the PoolableConnectionFactory, you'll need at least two things: 

A ConnectionFactory from which the actual database Connections will be obtained.
An empty and factory-less ObjectPool in which the Connections will be stored. 
 When you pass an ObjectPool into the PoolableConnectionFactory, it will automatically register itself as the PooledObjectFactory 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 PoolingDriver, we do the same thing, except that instead of creating a DataSource on the last line, we create a 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 PoolingDriver registers itself with the DriverManager when it is created, now you can just go to the DriverManager to create your Connections, like you normally would: 
Connection conn = DriverManager.getConnection("jdbc:apache:commons:dbcp:example");

/**
 * <p>
 * Database Connection Pool API.
 * </p>
 *
 * <b>Overview in Dialog Form</b>
 * <p>
 * Q: How do I use the DBCP package?
 * </p>
 * <p>
 * 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.dbcp2.PoolingDriver} or {@link org.apache.commons.dbcp2.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.
 * </p>
 * <p>
 * Q: But {@link org.apache.commons.dbcp2.PoolingDriver PoolingDriver} and
 * {@link org.apache.commons.dbcp2.PoolingDataSource PoolingDataSource} both expect an
 * {@link org.apache.commons.pool2.ObjectPool ObjectPool} as an input. Where do I get one of those?
 * </p>
 * <p>
 * A: The {@link org.apache.commons.pool2.ObjectPool ObjectPool} interface is defined in Commons Pool. You can use one
 * of the provided implementations such as {@link org.apache.commons.pool2.impl.GenericObjectPool GenericObjectPool},
 * {@link org.apache.commons.pool2.proxy.ProxiedObjectPool ProxiedObjectPool} or
 * {@link org.apache.commons.pool2.impl.SoftReferenceObjectPool SoftReferenceObjectPool} or you can create your own.
 * </p>
 * <p>
 * Q: Ok, I've found an {@link org.apache.commons.pool2.ObjectPool ObjectPool} implementation that I think suits my
 * connection pooling needs. But it wants a {@link org.apache.commons.pool2.PooledObjectFactory PooledObjectFactory}.
 * What should I use for that?
 * </p>
 * <p>
 * A: The DBCP package provides a class for this purpose. It's called
 * {@link org.apache.commons.dbcp2.PoolableConnectionFactory}. It implements the factory and lifecycle methods of
 * {@link org.apache.commons.pool2.PooledObjectFactory} for {@link java.sql.Connection}s. But it doesn't create the
 * actual database {@link java.sql.Connection}s itself, it uses a {@link org.apache.commons.dbcp2.ConnectionFactory} for
 * that. The {@link org.apache.commons.dbcp2.PoolableConnectionFactory} will take {@link java.sql.Connection}s created
 * by the {@link org.apache.commons.dbcp2.ConnectionFactory} and wrap them with classes that implement the pooling
 * behaviour.
 * </p>
 * <p>
 * Several implementations of {@link org.apache.commons.dbcp2.ConnectionFactory} are provided--one that uses
 * {@link java.sql.DriverManager} to create connections
 * ({@link org.apache.commons.dbcp2.DriverManagerConnectionFactory}), one that uses a {@link java.sql.Driver} to create
 * connections ({@link org.apache.commons.dbcp2.DriverConnectionFactory}), one that uses a {@link javax.sql.DataSource}
 * to create connections ({@link org.apache.commons.dbcp2.DataSourceConnectionFactory}).
 * </p>
 * <p>
 * Q: I think I'm starting to get it, but can you walk me though it again?
 * </p>
 * <p>
 * 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 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.dbcp2.PoolingDataSource}.
 * </p>
 * <p>
 * The {@link org.apache.commons.dbcp2.PoolingDataSource} uses an underlying {@link org.apache.commons.pool2.ObjectPool}
 * to create and store its {@link java.sql.Connection}.
 * </p>
 * <p>
 * To create a {@link org.apache.commons.pool2.ObjectPool}, you'll need a
 * {@link org.apache.commons.pool2.PooledObjectFactory} that creates the actual {@link java.sql.Connection}s. That's
 * what {@link org.apache.commons.dbcp2.PoolableConnectionFactory} is for.
 * </p>
 * <p>
 * To create the {@link org.apache.commons.dbcp2.PoolableConnectionFactory}, you'll need at least two things:
 * </p>
 * <ol>
 * <li>A {@link org.apache.commons.dbcp2.ConnectionFactory} from which the actual database {@link java.sql.Connection}s
 * will be obtained.</li>
 * <li>An empty and factory-less {@link org.apache.commons.pool2.ObjectPool} in which the {@link java.sql.Connection}s
 * will be stored. <br>
 * When you pass an {@link org.apache.commons.pool2.ObjectPool} into the
 * {@link org.apache.commons.dbcp2.PoolableConnectionFactory}, it will automatically register itself as the
 * {@link org.apache.commons.pool2.PooledObjectFactory} for that pool.</li>
 * </ol>
 * <p>
 * In code, that might look like this:
 * </p>
 *
 * <pre>
 * 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);
 * </pre>
 * <p>
 * To create a {@link org.apache.commons.dbcp2.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.dbcp2.PoolingDriver}, and
 * register the {@code connectionPool} with it. E.g.,:
 * </p>
 *
 * <pre>
 * 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);
 * </pre>
 * <p>
 * Since the {@link org.apache.commons.dbcp2.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:
 * </p>
 *
 * <pre>
 * Connection conn = DriverManager.getConnection("jdbc:apache:commons:dbcp:example");
 * </pre>
 */
package org.apache.commons.dbcp2;