How does a MDB client know ?

[Vipin Mohan]

hi friends

How does the client of an MDB know if a message has been delivered or not ?
I read about the various acknowledgement modes. But I'm not clear how the client receives the acknowledgement ? Are they received by the client as messages ?

Thanks
Vipin

[Nicholas Cheung]

How does the client of an MDB know if a message has been delivered or not ?

The client does not know whether a message has been delivered, just like SMS. You send out a message but you never know whether the receiver can get your message.

I read about the various acknowledgement modes. But I'm not clear how the client receives the acknowledgement ? Are they received by the client as messages ?

The acknowledgement is for the container, NOT the client. Remember, MDB does not have any client view, thus, the only client to MDB is the container!

Nick

[Vipin Mohan]

hi Nick

Thanks for the reply. I have one more question. According to specs-
Durable topic subscriptions ensure that messages are not missed even if the EJB server is not running, while non-durable ones don't.

Is there no acknowledgement sent in case of non-durable subscriptions ? If yes, then why doesn't it cause a redelivery of the message when no acknowledgement is received ?

Thanks
Vipin