Nobody answer, so I can assume that it is all correct ? :-)
I do not want to trigger a lengthy debate that might have already been discussed previously. I am just looking for some pointers if something is not right in the way I think the MDB are working with transactions.
Thanks.
Thomas
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, December 23, 2003 1:30 AM
To: [EMAIL PROTECTED]
Subject: [JBoss-user] Local/Global transaction with MDB
I am trying to list the different possible transaction options and behavior for a Message Driven that is also sending JMS messages as part of the logic of its onMessage operation. This subject has already been touched through multiple post in the mailing list, but I did not find any consolidated version. Here is what was able to determine so far. Please, feel free to comment, especially if something is not accurate.
Thanks.
Container-managed transaction
=======================
- The trans-attribute of the onMessage operation can be set to Required or NotSupported. I am not sure to understand the difference between the two since, in both cases, it seems that according
to the EJB specification, the reading of incoming messages will be done within a transaction created by the container. In the case of Jboss, it seems that if NotSupported is used, the messages
are read in a transaction but not in a global XA one (no messages can be sent as part of a global XA transaction from within the onMessage method). Can I expect that this behavior will be the same
on all app servers?
- The connection factory of the input destination must be an XA connection factory. This is not clearly stated by the spec, so I guess it is up to each app server. In the case of Jboss, I can use the
<xa-connection>false</xa-connection> in the jboss.xml to specify that it is not. In this case, the JBoss container will do a "regular" commit on the JMS session. A global transaction is still created
and JMS messages can be sent from within onMessage in this global transaction. When onMessage returns the global transaction is committed and then the input message session is committed.
- According to EJB spec, any JMS session open within a global transaction (open within a container managed transaction MDB) will be enlisted in the global transaction and the createXXXSession
parameters (boolean transacted, int acknowledgeMode) are ignored. It also means, I suppose, that the corresponding connectionFactory must be an XA connection factory. If a non-XA connection
factory is used, the behavior is probably app server specific. In the case of Jboss, if a non-XA connection factory is used (not JmsXA) the JMS session is not enlisted automatically and this is the
responsibility of the onMessage code to do the commit (or abort) on the JMS session (or to use auto-acknowledge JMS session).
- In the case of an exception thrown by onMessage (it is not supposed to happen, but just in case), any global transaction will be aborted. In the case the input message has been read in a regular JMS
transaction (Jboss specific when input destination connection factory is not XA or when NotSupported is used for trans-attribute) then this regular JMS transaction is also aborted.
Bean-managed transaction
====================
- This case is much simpler, a global transaction is never created by the container. The input JMS message is acknowledge before onMessage is called (according to the acknowledge-mode).
- JMS messages sent from the onMessage code are following the regular JMS rules for transaction. Multiple messages can be sent within one global transaction if this transaction is explicitly
created within the onMessage code (getUserTransaction) and provided that XA connection factories are used.
Thomas
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