EJB ( Enterprise Java Bean )

I have heard about EJB all the time since 5 years ago.
And yesterday I have found what it is.
It was actually not so complex.

I though it was a big library collection like STL or MFC.
But it wasn't.

The EJB technique reminded me of the memory pool technique in C++.
EJB container instantiates some of Bean classes, which is Business logic classes.
And then it manage them, allocate them, and release them.

There are three different types of beans: stateless, statefull and message driven.
I don't know the details for each one yet. But it must be basically same.

One can find good tutorial Here:
http://java.sun.com/javaee/5/docs/tutorial/doc/bnblt.html

I recommend one see the example files first:
http://java.sun.com/javaee/5/docs/tutorial/doc/bnbnb.html