pg. 497
Deepa Korecherla
Ranch Hand
Posts: 197
posted 12 years ago
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
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
DKR<br />SCJP1.2,SCWCD1.4,SCBCD1.3,SCJA
Miki Muzsi
Ranch Hand
Posts: 120
posted 12 years ago
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
But I agree it is a bit tricky, I have also wondered why only RequiresNew and not Required...
Miki
Miki<br /> <br />SCJP 1.4, SCBCD 1.3
Deepa Korecherla
Ranch Hand
Posts: 197
sawan parihar
Ranch Hand
Posts: 250
posted 12 years ago
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
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
Sawan<br />SCJP,SCWCD,SCBCD<br /> <br />Every exit is an entry somewhere.
Meg Adal
Ranch Hand
Posts: 70
Deepa Korecherla
Ranch Hand
Posts: 197
Amos Coats
Greenhorn
Posts: 9
posted 12 years ago
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!!!
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!!!
SCBCD SJP
