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package javax.sql;

import java.sql.Connection;
import java.sql.SQLException;


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 ConnectionPoolDataSource method getPoolConnection to create a new physical connection. The JDBC driver implementing ConnectionPoolDataSource creates a new PooledConnection object 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. 
 If the connection pool manager wraps or provides a proxy to the logical handle returned from a call to PoolConnection.getConnection, the pool manager must do one of the following when the connection pool manager closes or returns the PooledConnection to the pool in response to the application calling Connection.close: 
    

  • call endRequest on the logical Connection handle 
  • call close on the logical Connection handle 


 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. 
 A connection pool manager is often also a statement pool manager, maintaining a pool of PreparedStatement objects. When an application closes a prepared statement, it calls the PreparedStatement method close. When Statement pooling is being done, the pool manager is notified because it has registered itself as a StatementEventListener object using the ConnectionPool method addStatementEventListener. Thus, when an application closes its PreparedStatement, the underlying prepared statement is recycled rather than being closed. 
Since:1.4
/**
 * An object that provides hooks for connection pool management.
 * A {@code 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.
 * <P>
 * An application programmer does not use the {@code PooledConnection}
 * interface directly; rather, it is used by a middle tier infrastructure
 * that manages the pooling of connections.
 * <P>
 * When an application calls the method {@code DataSource.getConnection},
 * it gets back a {@code Connection} object.  If connection pooling is
 * being done, that {@code Connection} object is actually a handle to
 * a {@code PooledConnection} object, which is a physical connection.
 * <P>
 * The connection pool manager, typically the application server, maintains
 * a pool of {@code PooledConnection} objects.  If there is a
 * {@code PooledConnection} object available in the pool, the
 * connection pool manager returns a {@code Connection} object that
 * is a handle to that physical connection.
 * If no {@code PooledConnection} object is available, the
 * connection pool manager calls the {@code ConnectionPoolDataSource}
 * method {@code getPoolConnection} to create a new physical connection.  The
 *  JDBC driver implementing {@code ConnectionPoolDataSource} creates a
 *  new {@code PooledConnection} object and returns a handle to it.
 * <P>
 * When an application closes a connection, it calls the {@code Connection}
 * method {@code close}. When connection pooling is being done,
 * the connection pool manager is notified because it has registered itself as
 * a {@code ConnectionEventListener} object using the
 * {@code ConnectionPool} method {@code addConnectionEventListener}.
 * The connection pool manager deactivates the handle to
 * the {@code PooledConnection} object and  returns the
 * {@code 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.
 * <p>
 * If the connection pool manager wraps or provides a proxy to the logical
 * handle returned from a call to {@code PoolConnection.getConnection}, the pool
 * manager must do one of the following when the connection pool manager
 * closes or returns the {@code PooledConnection} to the pool in response to
 * the application calling {@code Connection.close}:
 * <ul>
 * <li>call {@code endRequest} on the logical {@code Connection} handle
 * <li>call {@code close} on the logical {@code Connection} handle
 * </ul>
 * <p>
 * The physical connection is not closed until the connection pool manager
 * calls the {@code PooledConnection} method {@code close}.
 * This method is generally called to have an orderly shutdown of the server or
 * if a fatal error has made the connection unusable.
 *
 * <p>
 * A connection pool manager is often also a statement pool manager, maintaining
 *  a pool of {@code PreparedStatement} objects.
 *  When an application closes a prepared statement, it calls the
 *  {@code PreparedStatement}
 * method {@code close}. When {@code Statement} pooling is being done,
 * the pool manager is notified because it has registered itself as
 * a {@code StatementEventListener} object using the
 * {@code ConnectionPool} method {@code addStatementEventListener}.
 *  Thus, when an application closes its  {@code PreparedStatement},
 * the underlying prepared statement is recycled rather than being closed.
 *
 * @since 1.4
 */

public interface PooledConnection {

  
Creates and returns a Connection object that is a handle for the physical connection that this PooledConnection object represents. The connection pool manager calls this method when an application has called the method DataSource.getConnection and there are no PooledConnection objects available. See the interface description for more information. 
Throws:
Returns: a Connection object that is a handle to this PooledConnection object
Since:1.4
/**
   * Creates and returns a {@code Connection} object that is a handle
   * for the physical connection that
   * this {@code PooledConnection} object represents.
   * The connection pool manager calls this method when an application has
   * called the method {@code DataSource.getConnection} and there are
   * no {@code PooledConnection} objects available. See the
   * {@link PooledConnection interface description} for more information.
   *
   * @return  a {@code Connection} object that is a handle to
   *          this {@code PooledConnection} object
   * @throws SQLException if a database access error occurs
   * @throws java.sql.SQLFeatureNotSupportedException if the JDBC driver does not support
   * this method
   * @since 1.4
   */
  Connection getConnection() throws SQLException;

  
Closes the physical connection that this PooledConnection object represents. An application never calls this method directly; it is called by the connection pool module, or manager. 
 See the interface description for more information. 
Throws:
Since:1.4
/**
   * Closes the physical connection that this {@code PooledConnection}
   * object represents.  An application never calls this method directly;
   * it is called by the connection pool module, or manager.
   * <P>
   * See the {@link PooledConnection interface description} for more
   * information.
   *
   * @throws SQLException if a database access error occurs
   * @throws java.sql.SQLFeatureNotSupportedException if the JDBC driver does not support
   * this method
   * @since 1.4
   */
  void close() throws SQLException;

  
Registers the given event listener so that it will be notified when an event occurs on this PooledConnection object. 
Params:
  • listener – a component, usually the connection pool manager, that has implemented the ConnectionEventListener interface and wants to be notified when the connection is closed or has an error
See Also:
/**
   * Registers the given event listener so that it will be notified
   * when an event occurs on this {@code PooledConnection} object.
   *
   * @param listener a component, usually the connection pool manager,
   *        that has implemented the
   *        {@code ConnectionEventListener} interface and wants to be
   *        notified when the connection is closed or has an error
   * @see #removeConnectionEventListener
   */
  void addConnectionEventListener(ConnectionEventListener listener);

  
Removes the given event listener from the list of components that will be notified when an event occurs on this PooledConnection object. 
Params:
  • listener – a component, usually the connection pool manager, that has implemented the ConnectionEventListener interface and been registered with this PooledConnection object as a listener
See Also:
/**
   * Removes the given event listener from the list of components that
   * will be notified when an event occurs on this
   * {@code PooledConnection} object.
   *
   * @param listener a component, usually the connection pool manager,
   *        that has implemented the
   *        {@code ConnectionEventListener} interface and
   *        been registered with this {@code PooledConnection} object as
   *        a listener
   * @see #addConnectionEventListener
   */
  void removeConnectionEventListener(ConnectionEventListener listener);

        
Registers a StatementEventListener with this PooledConnection object. Components that wish to be notified when PreparedStatements created by the connection are closed or are detected to be invalid may use this method to register a StatementEventListener with this PooledConnection object. 
Params:
  • listener –  an component which implements the StatementEventListener interface that is to be registered with this PooledConnection object
Since:1.6
/**
         * Registers a {@code StatementEventListener} with this {@code PooledConnection} object.  Components that
         * wish to be notified when  {@code PreparedStatement}s created by the
         * connection are closed or are detected to be invalid may use this method
         * to register a {@code StatementEventListener} with this {@code PooledConnection} object.
         *
         * @param listener      an component which implements the {@code StatementEventListener}
         *                                      interface that is to be registered with this {@code PooledConnection} object
         *
         * @since 1.6
         */
        public void addStatementEventListener(StatementEventListener listener);

        
Removes the specified StatementEventListener from the list of components that will be notified when the driver detects that a PreparedStatement has been closed or is invalid. 
Params:
  • listener –  the component which implements the StatementEventListener interface that was previously registered with this PooledConnection object
Since:1.6
/**
         * Removes the specified {@code StatementEventListener} from the list of
         * components that will be notified when the driver detects that a
         * {@code PreparedStatement} has been closed or is invalid.
         *
         * @param listener      the component which implements the
         *                                      {@code StatementEventListener} interface that was previously
         *                                      registered with this {@code PooledConnection} object
         *
         * @since 1.6
         */
        public void removeStatementEventListener(StatementEventListener listener);

 }