Can a Message Driven Bean Subscribe to Multiple Topics?

[rakesh]

Anyone know the answer to this? If so, how do you do it?

Rakesh

[pra]

No it cannot. It can only be tied to one destination. If you want one bean to act on messages frpm multiple destinations you would have to create a central destination and have one MDB per topic, each sending/retransmitting their messages to the central destination.

On the other hand, since it is only a matter of deplyment configuration to create a new deployable MDB for a new destination, you could have multiple MDB deploy (same bean class, different deployers and EJB names) listening on different destination.

//Peter

[rakesh]

Could you clarify a bit more. I don't think I understand.

Let's say I have a SSB (A), MDB (B) and a seperate java thread in its own JVM (C). C will only publish and subscribe to a single known topic. I want the following interaction. A sends a message to B. B sends a message to C. C then sends a response to B. The problem is the initial message from A also arrives a C, which I don't want. The message arrives at B and C is because B and C are listening to the same topic. Now you are saying to have a central MDB (D). A will send to D, D will discriminate the message and send it C based up information inside the message. When C sends a response it will be send to D, and D will again discriminate the message and send it to B. Is that right?

I don't think the other scenario applies in my case?

Regards

Rakesh

[pra]

> Could you clarify a bit more. I don't think I
> understand.
Ok, let's see if I understand your scenario ;-)

We call the destination TOPIC
>
> Let's say I have a SSB (A),

A client invokes A and A send a MESSAGE TO TOPIC
> MDB (B)
B listens on TOPIC does something and want to send it to C
>and a seperate
> java thread in its own JVM (C).

If B publish to C on TOPIC B will get its owm messages, if C respondes to B on TOPIC C will get its own messages.

Right?

As far as I can see it there are two possible solutions on this.

1. Do use separate detsinations. Since MDB:s are stateless there is really no advantage or need to have the send code and the response code in the same bean. I.e, you could actually have destination A (where the session publish and MDB B listens), destination B where B publish and client listens and C where C publish and MDB D listens.

2. The other way to do it is to use a message selector. I.e set a JMS property depending on who is sending and how should be receiving and set a message selector during subscription.

//Peter
C will only publish
> and subscribe to a single known topic. I want the
> following interaction. A sends a message to B. B
> sends a message to C. C then sends a response to B.
> The problem is the initial message from A also
> arrives a C, which I don't want. The message arrives
> at B and C is because B and C are listening to the
> same topic. Now you are saying to have a central MDB
> (D). A will send to D, D will discriminate the
> message and send it C based up information inside the
> message. When C sends a response it will be send to
> D, and D will again discriminate the message and send
> it to B. Is that right?
>
> I don't think the other scenario applies in my case?
>
> Regards
>
> Rakesh