/*

  * Copyright (C) The Apache Software Foundation. All rights reserved.

  *

  * This software is published under the terms of the Apache Software License

  * version 1.1, a copy of which has been included with this distribution in

  * the LICENSE file.

  * 

  * $Id: DefaultServerSessionPool.java 155459 2005-02-26 13:24:44Z dirkv $

  */

 package org.apache.commons.messenger;

 import java.util.LinkedList;

 import javax.jms.JMSException;

 import javax.jms.Message;

 import javax.jms.MessageListener;

 import javax.jms.ServerSession;

 import javax.jms.ServerSessionPool;

 import javax.jms.Session;

 /** <p><code>DefaultServerSessionPool</code> is a default implementation of

   * the JMS ServerSessionPool interface.</p>

   *

   * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>

   * @version $Revision: 155459 $

   */

 public class DefaultServerSessionPool implements ServerSessionPool {

     /** the list of ServerSession objects */

     private LinkedList list = new LinkedList();

     /** the factory used to create new Sessions */

     private SessionFactory sessionFactory;

     /** The MessageListener which are fired by new JMS Sessions */

     private MessageListener listener;    

     /** maximum blocking time, just in case a notify goes walkies */

     private long timeout = 5000;

     public DefaultServerSessionPool() {

     }

     public DefaultServerSessionPool(SessionFactory sessionFactory, MessageListener listener, int numberOfServerSessions) throws JMSException {

         this.sessionFactory = sessionFactory;

         this.listener = listener;

         for ( int i = 0; i < numberOfServerSessions; i++ ) {

             list.add( createServerSession() );

         }

     }

     /** Return a server session from the pool.

       *

       * @return a server session from the pool.

       *

       * @exception JMSException if a JMS error occurs.

       */

     public synchronized ServerSession getServerSession() throws JMSException {

         // we may want to grow if there are no sessions available

         while (list.isEmpty() ) {

             try {

                 wait( timeout );

             }

             catch(InterruptedException ex) {

                 // ignore

             }

         }

         return (ServerSession) list.removeFirst();

     }

     public synchronized void putServerSession(ServerSession serverSession) {

         list.addLast(serverSession);

         notify();

     }

     // Implementation methods

     //-------------------------------------------------------------------------        

     protected ServerSession createServerSession() throws JMSException {

         Session session = sessionFactory.createSession();

         final DefaultServerSession serverSession = new DefaultServerSession(session);

         session.setMessageListener( 

             new MessageListener() {

                 public void onMessage(Message message) {

                     try {

                         listener.onMessage(message);

                     }

                     finally {

                         // now give this session back to the pool

                         putServerSession( serverSession );

                     }

                 }

             }

         );        

         return serverSession;

     }

 }