MessageListenerSupport xref

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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  }