JBoss Service vs. EJB Application?

[platinumdragon]

Perhaps this is a basic question, and perhaps I just need a "Well, duh..." answer, but I haven't found another topic on this..

Under what circumstances would I want to write a JBoss service (MBeans) instead of an EJB application?

Thanks,
Mike

[vashistvishal]

As the name suggests MBeans are to manage beans..
So if u want to monitor the application written in JAVA u can write
manged beans, for that.

Where as EJB is more about encapsulating about business logic.
I hope this helps.

Vishal.

[platinumdragon]

But EJBs can also be MBeans. So, I guess what I'm asking is, what does an application get from being a JBoss service as opposed to just an EJB application?

Thanks,
Mike

[darranl]

Can you explain what you mean by 'But EJBs can also be MBeans', EJBs and MBeans are two completely different things.

[platinumdragon]

If by 'things' you mean concepts then yes, they are different things, but they are not exclusive of each other.

An MBean is simply a management interface for the underlying object. The interface has been registered with a lookup facility (MBeanServer derivative). The object itself can be anything: POJO, EJB, etc. Sometimes the object itself provides the management code, sometimes it delegates that code to a separate object (for instance, a 'manager' object). I just recently looked at a document that described this better, but I can't seem to locate it again. *drat*

Therefore, what I am referring to is an EJB that has registered itself as an MBean. If for instance, you had a small pool of stateful EJBs, you could monitor to see how many were in a certain state (like checking user activity across the application), or even allow you to reset that state. Obviously altering the lifetime of the EJB through the management interface would a bad thing, since you would be stepping the EJB containers toes, while wearing wooden shoes.

Now, with JBoss services (which AFAIK, must be an MBean), there is a separate descriptor stating when these services are started up and in what order. I am guessing that these should not be coded as EJBs, since something other than the EJB container is controlling their lifetime.

I hope this is somewhat clear, I think I even confused myself :)