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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 org.codehaus.activemq.util.JMSExceptionHelper;
21  
22  import javax.jms.JMSException;
23  
24  /***
25   * A helper class for ensuring that a number of tasks occur, whether they
26   * throw exceptions or not and saving the first exception so that we can
27   * throw it properly.
28   * This class is particularly useful for shutting things down, where we
29   * want to try close all resources, whether they fail or not.
30   *
31   * @version $Revision: 1.1 $
32   */
33  public class ExceptionTemplate {
34      private Throwable firstException;
35  
36      public ExceptionTemplate() {
37      }
38  
39      public void run(Callback task) {
40          try {
41              task.execute();
42          }
43          catch (Throwable t) {
44              if (firstException == null) {
45                  firstException = t;
46              }
47          }
48      }
49  
50      /***
51       * Returns the first exception thrown during the execution of this
52       * template or returns null if there has been no exception thrown yet.
53       *
54       * @return the first caught exception or null if none has occured yet
55       */
56      public Throwable getFirstException() {
57          return firstException;
58      }
59  
60      /***
61       * Throws the first exception caught during the execution of this template
62       * as a JMS exception or do nothing if we have not caught and exception
63       *
64       * @throws JMSException
65       */
66      public void throwJMSException() throws JMSException {
67          if (firstException != null) {
68              if (firstException instanceof JMSException) {
69                    throw (JMSException) firstException;
70              }
71              else if (firstException instanceof Exception) {
72                  throw JMSExceptionHelper.newJMSException(firstException.getMessage(), (Exception) firstException);
73              }
74              else {
75                  // lets wrap the Throwable in an Exception
76                  throw JMSExceptionHelper.newJMSException(firstException.getMessage(), new Exception(firstException));
77              }
78          }
79      }
80  }