Regarding JMS 2004-07-05 - By Binildas C. A.
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Answers to Query:
1. Referr to http://java.sun.com/blueprints/corej2eepatterns/
You will definitely find ServiceActivator pattern.
2. Drawbacks ! If we use MDB in scenarios where it is inappropriate, we
would face drawbacks. But that can be evaluated only on a case-by-case
basis.
3. TX - You can (with restrictions). But you need to check with the JMS
provider documentation, backing your MDB. Especially if it is a foreign JMS
provider, you need to check if you can propogate JMS transaction from within
your App Server to the foreign JMS provider. Single vendor solution
portfolio (like IBM WAS + MQ) would ususlly facilitate such TX propogation,
but in Mix-N-Max cases, we need to either follow vendor prescribed
procedures, or use workarounds.
A cleaner approach is to use MDB just as an Activator, and put all Business
Logic inside Stateless Session EJB. MDB in turn can delegate work to Session
EJB. Also, MDB is a listener, without any active clients, while Session EJBs
are not passive listeners, but needs to explicitely called by clients.
4. It depends upon your configuration settings. If the Queue is persistant
and if the onMessage() is in Transaction, a System Exception should re-try
with another instance of MDB (again depending upon Max. Number of tries
configured) - But, we need to look into vendor specific documentation, for
such QoS concerns.
Binildas
Sr. Tech.Architect
(http://www.infosys.com/setlabs)
-- -- Original Message -- --
From: "Kamaraj, Pushparaj" <Pushparaj_Kamaraj@(protected)>
To: <J2EEPATTERNS-INTEREST@(protected)>
Sent: Sunday, July 04, 2004 6:08 PM
Subject: Regarding JMS
> Hi,
> We are using weblogic JMS Queue and MDB in our system. I am having
> some questions on the same
> 1) Is there any pattern available for using message beans.
>
> 2) Where can I get the details about drawbacks of using MDB.
>
> 3) Can I use MDB as a normal stateless session bean including
> database transaction.
>
> 4) If any exception happens can the message will be retained so
that
> it will be served next time
>
>
> Thanks
> K.Pushparaj.
>
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