Head First EJB

It all starts with the home interface

The client wants the bean. Well, too bad. The client will never get the bean, because nobody talks to the bean (except the container). The best the client can hope for is a reference to the bean’s bodyguard—the component interface. And the client gets a reference to the bean’s component interface by calling a method on the bean’s home interface.

What the client REALLY wants is a reference to the bean. But the best the client can do is get a reference to the bean’s component interface--the EJB object^[6].

But if she wants an EJB object reference, the client has to get a reference to the bean’s home interface.

So that’s where it begins... the client does a lookup on the bean’s home.

There are no Dumb Questions

Q:	Q: How come you said, “And the client gets a reference to the bean’s component interface...” You can’t have a reference to an interface in Java—you can reference an object, but you can’t reference an interface. The reference variable can be declared as an interface type, but that’s not the same thing.
A:	A: Well, actually it is the same thing. In this book, and in the spec, and in the exam, everywhere you see the phrase, “reference to an interface”, do a mental search and replace to make it, “reference to an object that implements the interface.” It can feel a little strange, if you haven’t read documents that use this convention, but you better ...