/*

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

  */

 package org.apache.commons.messagelet;

 import java.net.URL;

 import java.util.Iterator;

 import javax.jms.JMSException;

 import javax.servlet.GenericServlet;

 import javax.servlet.ServletException;

 import javax.servlet.ServletRequest;

 import javax.servlet.ServletResponse;

 import org.apache.commons.messagelet.model.SubscriptionDigester;

 import org.apache.commons.messagelet.model.SubscriptionList;

 import org.apache.commons.messenger.Messenger;

 import org.apache.commons.messenger.MessengerManager;

 /** <p><code>ManagerServlet</code> manages the 

   * initialisation and destruction of the Messenger connections

   * and use of MessageListener beans for a given ServletContext.</p>

   *

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

   * @version $Revision: 155459 $

   */

 public class ManagerServlet extends GenericServlet {

     /** Should HTTP servlets be used or generic servlets. If true then JSP can be dispatched to easily */

     private static final boolean USE_HTTP_SERVLETS = true;

     private static final String KEY_CONNECTIONS = "connections";

     private static final String KEY_SUBSCRIPTIONS = "subscriptions";

     /** 

      * Whether exceptions occurring during subscriptions on startup should 

      * terminate the initialization

      */

     private boolean continueOnSubscribeException;

     public ManagerServlet() {

     }

     public SubscriptionManager getSubscriptionManager() {

         SubscriptionManager answer = (SubscriptionManager) getServletContext().getAttribute( "subscriptionManager" );

         if (answer == null) {

             answer = new SubscriptionManager();

             getServletContext().setAttribute( "subscriptionManager", answer );

         }

         return answer;

     }

     // Servlet methods

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

     public synchronized void init() throws ServletException {        

         String text = getServletContext().getInitParameter( "continueOnSubscribeException" );

         if ( text != null && text.equals( "true" ) ) {

             continueOnSubscribeException = true;

         }

         // ensure Messenger is initialised

         try {

             SubscriptionManager subscriber = getSubscriptionManager();

             MessengerManager manager = subscriber.getMessengerManager();

             if ( manager == null ) {

                 manager = createMessengerManager();

                 subscriber.setMessengerManager( manager );

                 subscriber.setSubscriptionList( createSubscriptionList() );

                 subscriber.setServletContext( getServletContext() );

                 // load the subscriptions....

                 subscriber.subscribe();

                 // now lets start all the connections...

                 for (Iterator iter = manager.getMessengerNames(); iter.hasNext(); ) {

                     String name = (String) iter.next();

                     Messenger messenger = manager.getMessenger( name );

                     try {

                         messenger.getConnection().start();

                     }

                     catch (JMSException e) {

                         log( "Caught exception trying to start messenger: " + name + ". Exception: " + e, e );

                     }

                 }

             }

         }

         catch (JMSException e) {

             throw new ServletException("Failed to initialize: " + e, e );

         }

     }

     public void destroy() {

         try {

             getSubscriptionManager().unsubscribe();

         }

         catch (Exception e) {

             log( "Failed to destrory the MBOs: " + e, e );

         }

         try {        

             MessengerManager manager = getSubscriptionManager().getMessengerManager();

             if ( manager != null ) {

                 log( "Closing the Messenger connections" );

                 manager.close();

             }

         }

         catch (Exception e) {

             log( "Failed to close the Messenger Manager: " + e, e );

         }

         getSubscriptionManager().setMessengerManager( null );

     }

     public void service(ServletRequest request, ServletResponse response) throws ServletException {

     }

     // Properties

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

     public boolean isContinueOnSubscriptionException() {

         return continueOnSubscribeException;

     }

     /** 

      * Sets whether exceptions occurring during subscriptions on startup should 

      * terminate the initialization

      */

     public void setContinueOnSubscribeException(boolean continueOnSubscribeException) {

         this.continueOnSubscribeException = continueOnSubscribeException;

     }

     // Implementation methods

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

     protected MessengerManager createMessengerManager() throws ServletException {

         String config = getURLResource( KEY_CONNECTIONS, "The Messenger connections XML deployment document" );

         log( "Creating the Messenger connections from the file: " + config );

         try {

             return MessengerManager.load( config );

         }

         catch (JMSException e) {

             log( "Could not parse Messenger connection XML deployment document for URL: " + config, e );

             throw new ServletException(

                 "Could not parse Messenger connection XML deployment document for URL: " + config

                 + " reason: " + e, e

             );

         }

     }

     protected SubscriptionList createSubscriptionList() throws ServletException {

         String config = getURLResource( KEY_SUBSCRIPTIONS, "The Messenger subscriptions XML deployment document" );

         log( "Loading the Messenger subscriptions from: " + config );

         try {

             SubscriptionDigester digester = new SubscriptionDigester();

             return (SubscriptionList) digester.parse( config );

         }

         catch (Exception e) {

             log( "Could not parse Messenger subscription XML deployment document for URL: " + config, e );

             throw new ServletException(

                 "Could not parse Messenger subscription XML deployment document for URL: " + config

                 + " reason: " + e, e

             );

         }

     }

     protected String getURLResource(String key, String description) throws ServletException {

         String config = getInitParameter( key );

         if ( config == null || config.length() == 0 ) {

             throw new ServletException( 

                 "No initialization parameter for parameter: " + key 

                 + " description: " + description 

             );

         }

         try {

             URL url = getServletContext().getResource( config );

             config = url.toString();

         }

         catch (Exception e) {

             // ignore, must be an absolute URL

         }

         return config;

     }

     /**

      * Allows derived servlets to handle JMS exceptions differently, such as ignoring certain kinds of

      * exceptions or performing custom logging etc.

      */

     protected void handleJMSException(String message, JMSException exception) throws ServletException {    

         log( message, exception );

         if ( ! isContinueOnSubscriptionException() ) {

             throw new ServletException( message, exception );

         }

     }

 }