MOM question

[Timber Lee]

which can be used as MOM client?
1.EJB
2.applet
3.JSP
4.Servlet
5.MDB

[SJ Adnams]

an applet is the most likely.
EJB is also possible (now), but in the exam version of EJB it's not allowed.
(whats an MBD?)
Simon

[Chris Mathews]

MDB = Message Driven Bean which is part of the EJB 2.0 Specification.

[Naichen Liu]

Maybe all of them are correct,
MDB could act as message consumer, and others could be producers.

[Eduard Manas]

Everything that can use JMS is a potential MOM client, so I'd say them all are correct.
MOM servers is a different story though... and the answer to that auto-asked question is just MDB.

[Byron Estes]

Be careful don't confuse client -> server with message producer -> consumer. Remember the MOM sits in the middle as a topic or queue. Whether you produce or consume, you interact with MOM. As a result, you could interpret the relationship so that the MOM (i.e. MQSeries, SonicMQ, etc.) is the only real server and all those other things (i.e. applets, jsp, session beans, mdb, etc...) are clients that either produce and/or consume. Remember a mdb is simply a way of easily creating a long running listener to a topic/queue. You can implement the JMS interfaces yourself and create your own listener, but it's more work because you have to provide it a means of staying alive and therefore you must deal with it's lifecycle.
Regards,

[Chris Mathews]

Originally posted by Eduard Manas:
Everything that can use JMS is a potential MOM client, so I'd say them all are correct.
MOM servers is a different story though... and the answer to that auto-asked question is just MDB.
What if the MOM server does not support JMS?
My point is, the term MOM is not synonymous with JMS. There are plenty of MOM servers that do not support the JMS spec. This question should have really been worded, "Which can be used as JMS client?"

[Shankar Shanmugam]

Hi,
I have a basic question which is not related to MOM/MDB. Just wanted to know the J2EE/EJB version covered in the SCEAJ exam.
Thanks in Advance,
Shankar Shanmugam

[Eduard Manas]

Originally posted by Byron Estes:
[QB]Be careful don't confuse client -> server with message producer -> consumer. [QB]

Thanks for your correction Byron, now that I think about it I agree with you and I don't think the term 'MOM server' is correct. To me 'MOM server' sounds more like part of the MOM itself.
I'd say you should call it either message consumer, or topic subscriber. The problem here is how would you call the entity/process/piece of code that is listening for messages coming from a MOM, without mentioning whether they are using queue or topic. You cannot call it consumer or subscriber.
Does anyone know whether there is a name for it?
Eduard

[Eduard Manas]

What if the MOM server does not support JMS?

... well, in that case you are screwed! ...or maybe not?
I suppose that you could encapsulate the asynchronous call with a DAO using the third-party specific protocol. In that case you could also use it from anywhere that has access to the DAOs.

My point is, the term MOM is not synonymous with JMS. There are plenty of MOM servers that do not support the JMS spec.

I agree, but I wouldn't expect that the examiners expect you to assume that, first of all because all major MOM vendors provide JMS interfaces. In other words, if they don't tell you otherwise, I would assume there is a JMS driver for it.

This question should have really been worded, "Which can be used as JMS client?"

That sounds much better!
Eduard

[Byron Estes]

Actually, if you look at the JMS API in J2EE 1.4 you'll find two interfaces of interest: MessageConsumer and MessageProducer.
Each of these have subinterfaces specific to whether you are dealing with a topic or a queue.
MessageConsumer
- QueueReceiver
- TopicSubscriber
MessageProducer
- QueueSender
- TopicPublisher
Regards,