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1   /*** 
2    * 
3    * Copyright 2004 Protique Ltd
4    * 
5    * Licensed under the Apache License, Version 2.0 (the "License"); 
6    * you may not use this file except in compliance with the License. 
7    * You may obtain a copy of the License at 
8    * 
9    * http://www.apache.org/licenses/LICENSE-2.0
10   * 
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS, 
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
14   * See the License for the specific language governing permissions and 
15   * limitations under the License. 
16   * 
17   **/
18  package org.codehaus.activemq.util;
19  
20  import javax.jms.ExceptionListener;
21  import javax.jms.JMSException;
22  import javax.jms.Message;
23  import javax.jms.MessageListener;
24  
25  /***
26   * A helper base class which makes writing message listeners easier without
27   * having to worry about handling the JMSException on the onMessage() method.
28   * By default the JMS ExceptionListener will be used to handle any JMS exceptions
29   * or if none is configured then a runtime exception will be generated.
30   *
31   * @author James Strachan
32   * @version $Revision: 1.2 $
33   */
34  public abstract class MessageListenerSupport implements MessageListener {
35      private ExceptionListener exceptionListener;
36  
37      public void onMessage(Message message) {
38          try {
39              processMessage(message);
40          }
41          catch (JMSException e) {
42              onJMSException(e, message);
43          }
44          catch (Exception e) {
45              // lets wrap the exception
46              JMSException jmsEx = JMSExceptionHelper.newJMSException(e.getMessage(), e);
47              onJMSException(jmsEx, message);
48          }
49      }
50  
51      public ExceptionListener getExceptionListener() {
52          return exceptionListener;
53      }
54  
55      public void setExceptionListener(ExceptionListener exceptionListener) {
56          this.exceptionListener = exceptionListener;
57      }
58  
59      /***
60       * This method processes the incoming message possibly throwing a JMSException
61       * if the message could not be processed correctly.
62       *
63       * @param messsage
64       * @throws Exception
65       */
66      protected abstract void processMessage(Message messsage) throws Exception;
67  
68      /***
69       * Process the JMS exception either by calling an exception listener
70       * which can contian custom logic or by throwing a runtime exception
71       *
72       * @param e
73       * @param message
74       */
75      protected void onJMSException(JMSException e, Message message) {
76          if (exceptionListener != null) {
77              exceptionListener.onException(e);
78          }
79          else {
80              throw new RuntimeException("Failed to process message: " + message + " Reason: " + e, e);
81          }
82      }
83  
84  }