[jboss-user] [Messaging, JMS & JBossMQ] - DLQ and caught exception in onMessage

[torsty]

Hi, I have the following problem: I have a MDB (EJB 3.0 on AS: 4.0.5.GA) that consumes messages from a queue. In the onMessage method I am calling the method of a Stateless Session Bean (injected with SEAM-mechanism). 


  | public void onMessage( Message msg )
  | {
  |  
  |   // extract userId and type from msg - both string variable
  |   try{
  | 	this.requestManager.insert(userId, type) // stateless session bean injected with seam
  |   catch ( JMSException e ){
  | 	e.printStackTrace();
  |   }
  | }
  | 

The insert Method is as follows:

  | public void insertPemRequest( String userId, String type )
  | {
  |  Person person = new Person( userId, type );
  |  try
  |  {
  |   this.entityManager.persist( examRequest );
  |   this.entityManager.flush();
  | 
  |   // create business process in jbpm
  |  }
  |  catch ( ConstraintViolationException exp ){
  |     // do nothing, i.e do not kick off new business process
  |  }
  |  catch ( EntityExistsException entityEx ) {
  |     // do nothing, i.e do not kick off new business process
  |  }
  | }
  | 

The Person Bean has unique constraint on userId and type: i.e:

  | @Entity
  | @Table( uniqueConstraints= {@UniqueConstraint(columnNames={"userId", "type"}) } )
  | public class Person {
  | // ---- getter/setter for id, name, type
  | }
  | 

By catching the EntityExistsException I want to avoid that a business process is kicked off twice for the same person and type. As there might be many messages send and consumed in parallel all requesting to kick off a business process for one person  and type combination - this is a good way to control that a business process is kicked off once and once only for a name/type combination.

Now my problem: The message is still redelivered and send to the DLQ, altough I caught the EntityExistsException. All other exceptions should lead to sending the message to DLQ. But not the EntityExistsException as this is a "tolerated" exception. I know from FAQ

anonymous wrote : 
  |  What type of Exceptions should an MDB throw?
  |  The quick answer is none. 
  | 

But I am catching the exception. right? Or is this correct behaviour and I have to change my design that no EntityExistsException is thrown? 

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