Message-driven beans Vs JMS

Question

Hi,
what does the bean technology add to the JSM by using the message driven beans instead of just using the regular asynchronus JMS?

Answer 1

that's my question when and why should we chose:
1. simple asynchronous JMS
2. message-driven beansYou presumably mean:
1. "simple" JMS client
2. MDB JMS client
That'll depend first on your existing architecture.You'll go for the second option if you're already using EJB , as to leverage your existing IT investment.
Second, the EJB container gives you a number of services, so you don't have to worry about those yourself: life cycle management, scalability, transaction support, concurrency etc..
With a plain JMS client, you'll have to handle concurrency yourself, for example, by spawning different JMS instances.
If you're using an EJB container, that container will instantiate multiple MDB instances to handle multiple messages simultaneously.
OTOH, The EJB contract implies some limitations of use. For example, an MDB can be associated with only one queue or topic. So if you need a JMS client to be able to handle multiple queues ot topics, you'll need to create multiple MDB clients, or go for a simple non-MDB JMS consumer.