Originally posted by raj malhotra:
Connection pool does not contain the connection object of type Connection but PooledConnection.
public interface PooledConnection
An object that provides hooks for connection pool management. A PooledConnection object represents a physical connection to a data source. The connection can be recycled rather than being closed when an application is finished with it, thus reducing the number of connections that need to be made.
An application programmer does not use the PooledConnection interface directly; rather, it is used by a middle tier infrastructure that manages the pooling of connections.
When an application calls the method DataSource.getConnection, it gets back a Connection object. If connection pooling is being done, that Connection object is actually a handle to a PooledConnection object, which is a physical connection.
The connection pool manager, typically the application server, maintains a pool of PooledConnection objects. If there is a PooledConnection object available in the pool, the connection pool manager returns a Connection object that is a handle to that physical connection. If no PooledConnection object is available, the connection pool manager calls the PooledConnection method getConnection to create a new physical connection and returns a handle to it.
When an application closes a connection, it calls the Connection method close. When connection pooling is being done, the connection pool manager is notified because it has registered itself as a ConnectionEventListener object using the ConnectionPool method addConnectionEventListener. The connection pool manager deactivates the handle to the PooledConnection object and returns the PooledConnection object to the pool of connections so that it can be used again. Thus, when an application closes its connection, the underlying physical connection is recycled rather than being closed.
The physical connection is not closed until the connection pool manager calls the PooledConnection method close. This method is generally called to have an orderly shutdown of the server or if a fatal error has made the connection unusable.