Catching Mysql sql execution status with EJB and Persistence API.

Question

Hi:
When I insert a duplicate unique Key, the try block defined below does not catch the exception and the transaction is rolled back automatically by Glassfish.
How is the proper way to handle this to catch the duplicate status?
public class MyDbEjb extends DefaultHandler implements MyDbEjbRemote {     @PersistenceContext     private EntityManager em;     public void createTag(Tag tag) {       try {         em.persist(tag);       } catch ( Exception e)       {           System.out.println("how sorry");       }           }
Thank you

Answer 1

Hi annie,
Wherever you are handling database transactions,
you'd not be able to create a Connection if database
is closed (I think you mentioned turning off the
database) then at this condition, you should
certainly throw a System level exception and stop all
processing with some meaningful flow to indicate a
failure (like display message on UI). Even
network problems are handled by exceptions... so I
don't see a reason why you didn't wrap it in the
first place.
Anyway, try handling specific exceptions rather than
the general Exception... this will give you a better
idea of what to do in case of an exception.Yes i know this. I am practicing this in my non-j2ee server applications. But the j2ee app im making, i just pass the db url in the descriptor and the app server automatically creates the connection for my app. So where would i put exception handling?
2. how can i stop my MDB from processing the same
message?Guaranteed delivery is not supposed to stop
processing. It will continue to process the message
after certain intervals till the message is
delivered. You shouldn't deliver it at all, if you
are able to detect that the database is off
The problem here is that my MDB automatically retrieves the message from the JMS queue server. Im not the one retrieving the messages manually.
My assumed behavior of topic MDB is once the a certain MDB retrieves a message it will not retrieve the same message anymore.
thank you in advance.
leigh