Handling errors

 

---

Any runtime errors in a JMS application are reported by exceptions. The majority of methods in JMS throw JMSExceptions to indicate errors. It is good programming practice to catch these exceptions and display them on a suitable output.

A JMSException can contain a further exception embedded in it. For JMS, this can be a valuable way to pass important detail from the underlying transport. In the case of WebSphere MQ JMS, when WebSphere MQ raises an MQException, this exception is usually included as the embedded exception in a JMSException.

The implementation of JMSException does not include the embedded exception in the output of its toString() method. Therefore, it is necessary to check explicitly for an embedded exception and print it out, as shown in the following fragment:

try {
  .
  . code which may throw a JMSException
  .
} catch (JMSException je) {
  System.err.println("caught "+je);
  Exception e = je.getLinkedException();
  if (e != null) {
    System.err.println("linked exception: "+e);
  }
}

 

Exception listener

For asynchronous message delivery, the application code cannot catch exceptions raised by failures to receive messages. This is because the application code does not make explicit calls to receive() methods. To cope with this situation, it is possible to register an ExceptionListener, which is an instance of a class that implements the onException() method. When a serious error occurs, this method is called with the JMSException passed as its only parameter. Further details are in Sun's JMS documentation.

 

WebSphere is a trademark of the IBM Corporation in the United States, other countries, or both.

 

IBM is a trademark of the IBM Corporation in the United States, other countries, or both.