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How does a MDB client know ?

Vipin Mohan
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Joined: Nov 15, 2003
Posts: 79
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
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Joined: Nov 07, 2003
Posts: 4982

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


SCJP 1.2, OCP 9i DBA, SCWCD 1.3, SCJP 1.4 (SAI), SCJD 1.4, SCWCD 1.4 (Beta), ICED (IBM 287, IBM 484, IBM 486), SCMAD 1.0 (Beta), SCBCD 1.3, ICSD (IBM 288), ICDBA (IBM 700, IBM 701), SCDJWS, ICSD (IBM 348), OCP 10g DBA (Beta), SCJP 5.0 (Beta), SCJA 1.0 (Beta), MCP(70-270), SCBCD 5.0 (Beta), SCJP 6.0, SCEA for JEE5 (in progress)
Vipin Mohan
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Joined: Nov 15, 2003
Posts: 79
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
 
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