JMS - Use question

Question

Hey Folks,
Just reading a book on JMS for the first time and i just have a few philosophical questions on the use of it. In the book it gives me an example of setting up a JMS queue and then using a MDB to receive a message and then does a credit check on a customer!!
So after one has gone through all the hassle of configuring your factories,setting up your queue, creating your MDB and then configuring it your are finally ready to write code to do your business requirements!!
Now my first thought were, why would i do all that work just to do a credit check on a customer asynchronously, if i was using plain old POJO�s , why wouldnt i just spin off a thread to do this for me in the backround instead of having to do all the above?? So what am i missing here??
Next point that i need some clarity on is more related to a production setup. Say i have 10 nodes, does one just create one JMS channel that all 10 nodes use or do they each have a channel for every node?? If they have a channel for every node then why would i use JMS?? Ok loose coupling, great but i can get that if i create my own observer pattern, what extra will it give me than a normal observer pattern?? I assume in the above scenario that you have no external applications listening, so everything that needs to listen for the message is in your JVM!! I understand if you have SAP or any other external applications listening
Last but not least, is it fair to make a comparison JMS to tibco messaging bus?? If so why, if not why?? ;)
Thanks for any help on the matter, like i said im just reading up on it now and need a few thoughts cleared up!!
Cheers,
LL

Answer 1

> So when you say chained, i take it you can set the
order in which you want your beans to be called
first(assuming in a topic scenario where you have
several listeners)?? is that possible with JMS?? if
so how??
We've written a custom Process Manager that receives messages and uses XPath and XSL to coordinate several JMS applications (all of our messages are XML). We typically don't use topics because we don't want multiple applications getting the same message. Each application does its work in turn, not at the same time.
> Yeh i can see how it would work in this scenario but
you still have other options to solve this problem
without the need of JMS!!
There's always more than one way to solve a problem.
> i suppose im looking for a scenario where i would say
to myself, yes thats a job for JMS!! And in this
scenario exclude the need to talk to external
applications!!
I wouldn't want to design a large system with multiple teams working on multiple applications, each with its own processing needs without JMS. Tuning is pretty easy. Adding more horsepower at any point in the chain is pretty easy.
But it may be that I just reach for the tools that I am most familiar with.
Dwayne