pg. 497

[Deepa Korecherla]

In 2nd Q --which tx attibute must not be used for MDB??
The ans -- ReqNew,Mand,Never,Supports
I don't understnd how is that??

Mand & Never throws exception ok fine...
Then what about supports & Reqnew??
I thought for MDB there should not be any previous tx context ..so, Supports must not be used .ok fine again
then why ReqNew?? & why not Required??

can anyone understand my point?? if yes, pls reply & clarify where I'm wrong

[Miki Muzsi]

Required means that the bean is running in the tx from the incomming request, or in a new one if there is no incomming tx. But for MDB there is no incomming request, since there is no client! So RequiresNew is a "cleaner" definition in a way...

But I agree it is a bit tricky, I have also wondered why only RequiresNew and not Required...

Miki

[Deepa Korecherla]

I guess ReqNew can be used rather than Required... b'coz its not required to run in the previous tx for MDB.
Can anyone clarify?? I'm confused!!!

[sawan parihar]

Hi,
There is nothing written in specs that why RequiresNew can't be used but I think the possible reason is that in case of MDB with CMT the message receipt is included as a part of the bean's transaction . That means (message receipt + onMessage()) makes on transaction. If the specs would have allowed RequiresNew then you can see the problem with the message receipt.

This is what I think and I haven't read it anywhere .

Sawan
SCJP,SCWCD,SCBCD

[Meg Adal]

https://coderanch.com/t/160802/java-EJB-SCBCD/certification/MDB-transaction-attribute

[Deepa Korecherla]

Thank you all for all ur replies!!
I guess I have to remember MDB must use only Required & Not Supported
Required & Not Supported
Required & Not Supported
Required & Not Supported
Required & Not Supported

[Amos Coats]

Hey it easy to figure out why if you know that a MDB is never called in Tx of a client.
So then the logic is:

ReqNew - does not make sense since the is no "old" transaction

Mand - if you specify this the method will alway throw an exception of course this can never be what you want

Never - This is allways the case so why should you specify it again? you specify Never to throw an exception when a method is called in Tx context, bit this nver happens with a MDB so why specify Never

Supports - There is no client Tx to Support!!!