/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * <p>
 * Database Connection Pool API.
 * </p>
 * <strong>Overview in Dialog Form</strong>
 * <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.tomcat.dbcp.dbcp2.PoolingDriver} or {@link org.apache.tomcat.dbcp.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.tomcat.dbcp.dbcp2.PoolingDriver PoolingDriver} and
 * {@link org.apache.tomcat.dbcp.dbcp2.PoolingDataSource PoolingDataSource} both expect an
 * {@link org.apache.tomcat.dbcp.pool2.ObjectPool ObjectPool} as an input. Where do I get one of those?
 * </p>
 * <p>
 * A: The {@link org.apache.tomcat.dbcp.pool2.ObjectPool ObjectPool} interface is defined in Commons Pool. You can use one
 * of the provided implementations such as {@link org.apache.tomcat.dbcp.pool2.impl.GenericObjectPool GenericObjectPool} or
 * {@link org.apache.tomcat.dbcp.pool2.impl.SoftReferenceObjectPool SoftReferenceObjectPool} or you can create your own.
 * </p>
 * <p>
 * Q: Ok, I've found an {@link org.apache.tomcat.dbcp.pool2.ObjectPool ObjectPool} implementation that I think suits my
 * connection pooling needs. But it wants a {@link org.apache.tomcat.dbcp.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.tomcat.dbcp.dbcp2.PoolableConnectionFactory}. It implements the factory and lifecycle methods of
 * {@link org.apache.tomcat.dbcp.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.tomcat.dbcp.dbcp2.ConnectionFactory} for
 * that. The {@link org.apache.tomcat.dbcp.dbcp2.PoolableConnectionFactory} will take {@link java.sql.Connection}s created
 * by the {@link org.apache.tomcat.dbcp.dbcp2.ConnectionFactory} and wrap them with classes that implement the pooling
 * behaviour.
 * </p>
 * <p>
 * Several implementations of {@link org.apache.tomcat.dbcp.dbcp2.ConnectionFactory} are provided--one that uses
 * {@link java.sql.DriverManager} to create connections
 * ({@link org.apache.tomcat.dbcp.dbcp2.DriverManagerConnectionFactory}), one that uses a {@link java.sql.Driver} to create
 * connections ({@link org.apache.tomcat.dbcp.dbcp2.DriverConnectionFactory}), one that uses a {@link javax.sql.DataSource}
 * to create connections ({@link org.apache.tomcat.dbcp.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.tomcat.dbcp.dbcp2.PoolingDataSource}.
 * </p>
 * <p>
 * The {@link org.apache.tomcat.dbcp.dbcp2.PoolingDataSource} uses an underlying {@link org.apache.tomcat.dbcp.pool2.ObjectPool}
 * to create and store its {@link java.sql.Connection}.
 * </p>
 * <p>
 * To create a {@link org.apache.tomcat.dbcp.pool2.ObjectPool}, you'll need a
 * {@link org.apache.tomcat.dbcp.pool2.PooledObjectFactory} that creates the actual {@link java.sql.Connection}s. That's
 * what {@link org.apache.tomcat.dbcp.dbcp2.PoolableConnectionFactory} is for.
 * </p>
 * <p>
 * To create the {@link org.apache.tomcat.dbcp.dbcp2.PoolableConnectionFactory}, you'll need at least two things:
 * </p>
 * <ol>
 * <li>A {@link org.apache.tomcat.dbcp.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.tomcat.dbcp.pool2.ObjectPool} in which the {@link java.sql.Connection}s
 * will be stored. <br>
 * When you pass an {@link org.apache.tomcat.dbcp.pool2.ObjectPool} into the
 * {@link org.apache.tomcat.dbcp.dbcp2.PoolableConnectionFactory}, it will automatically register itself as the
 * {@link org.apache.tomcat.dbcp.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");
 * ObjectName oName = new ObjectName("MyTests:DataSource=test"); // or null to not use JMX
 * PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory(connectionFactory, oName);
 * PoolingDataSource dataSource = new PoolingDataSource(connectionPool);
 * </pre>
 * <p>
 * To create a {@link org.apache.tomcat.dbcp.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.tomcat.dbcp.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");
 * ObjectName oName = new ObjectName("MyTests:DataSource=test"); // or null to not use JMX
 * PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory(connectionFactory, oName);
 * PoolingDriver driver = new PoolingDriver();
 * driver.registerPool("example", connectionPool);
 * </pre>
 * <p>
 * Since the {@link org.apache.tomcat.dbcp.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.tomcat.dbcp.dbcp2;
