JavaServer Pages, 3rd Edition

Using a JDBC 2.0 Optional Package Connection Pool

Connection pools exist in many forms. You find them in books, articles, and on the Web. Yet prior to JDBC 2.0, there was no standard defined for how a Java application would interact with a connection pool. The JDBC 2.0 Optional Package (formerly known as a Standard Extension), now part of JDBC 3.0 and included in the Java SDK 1.4, changed this by introducing a set of interfaces that connection pools should implement:

javax.sql.DataSource

A DataSource represents a database. This is the interface the application always uses to get a Connection. The class that implements the interface can provide connection-pooling capabilities or hand out regular, unpooled Connection objects; the application code is identical for both cases, as described later.

javax.sql.ConnectionPoolDataSource

A DataSource implementation that provides pooling capabilities uses a class that implements the ConnectionPoolDataSource interface. A ConnectionPoolDataSource is a factory for PooledConnection objects. The application code never calls methods in this interface directly.

javax.sql.PooledConnection

The objects a DataSource with pooling capabilities keeps in its pool implement the PooledConnection interface. When the application asks the DataSource for a Connection, it locates an available PooledConnection object or gets a new one from its ConnectionPoolDataSource if the pool is empty.

The PooledConnection provides a getConnection( ) method that returns a Connection ...