Richard,
We discussed this quite extensively with Sun a while back and came to the
conclusion that it was best to provide the customer with proprietary
(declarative) mechanisms to specify the number of times to retry delivery
of messages to BMT/NotSupported message listeners which 'fail', and to
provide a "dead message" area into which such messages would be placed
if they cannot be successfully processed according to the retry count.
Richard Monson-Haefel wrote:
>
> The EJB 2.0 specification doesn't say when a message is acknowledge with
> Auto-acknowledgment in BMT message-driven beans (MDB). This is somewhat
> understandable since JMS itself is somewhat ambiguous about the exact
> timing of AUTO_ACKNOWLEDGMENT mode. However, it makes a big difference
> in EJB 2.0 if the message is acknowledged before the message is
> delegated to the MDB instance or after. With Auto-acknowledgment, I
> would make the assumption that the message is acknowledged before
> delegating the message to the client, or shortly there after regardless
> of the out come of the onMessage() method (normal return vs. exception
> thrown).
>
> It would be better, however, if it occurred after the successful
> completion of the onMessage() method to allow redelivery of the message
> in the advent of a failure while handling the message. In other words,
> if the MDB throws an exception from the onMessage() method, the receipt
> of the message should not be acknowledged by the EJB container. In BMT
> MDB where message acknowledgment is not a part of the transaction commit
> processes, a failure to acknowledge the message would allow it to be
> redelivered and not lost. This is also true of container-managed
> transactions where the transaction attribute is NotSupported. This is
> something that should be clarified in the specification or at least
> addressed.
>
> I would be interested in hearing Sun Microsystems comments on this as
> well as the vendors. How are vendors handling this? How does the EJB
> 2.0 spec team feel it should be handled?
>
> Thanks,
>
> Richard
> --
> Richard Monson-Haefel
> Author of Enterprise JavaBeans, 2nd Edition (O'Reilly 2000)
> Co-Author of Java Message Service (O'Reilly 2000)
> http://www.jMiddleware.com
--
________________________________________________________________________________
Evan Ireland Sybase EAServer Engineering [EMAIL PROTECTED]
Wellington, New Zealand +64 4 934-5856
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