How does Ejb maintain relationship

Question

How does EJB maintain a link between the EJBRemoteObject,EJBHome and
the EJBClass
and why does EJBClass implements SessionBean and the rest of the classes extend a paticular classes.
What is their relation.

Answer 1

EJBRemoteObject (or EJBObject) and EJBLoclaObject are interfaces that user can use to access an object. If you use remote object user can access the object remotely. Local object can be accessed remotely only via another session bean that locates in the JVM of local bean and implements remote interface.
The EJBHome and EJBLocalHome are factories of objects. User uses them like:
UserHome userHome = JNDI.getRootContext().getObject("EJB/UserBean").narrow(UserHome.class);
User user = userHome.create("Andreas", "Papandreas");
user.setRole("admin");
// here UserHome is interface extending EJBHome
// here User is interface extending EJBObject
// User looks like EntityBeanEJBClass that implement SessionBean or EntityBean are abstract classes. They will be extended by application server. The application server creates stubs for client JVM as well. These subs marshall data to EJBClass on server. You may override some methods in EJBClass, for example initializing some fields on object creation. Setters and getters (required in entity beans) remain abstract in the EJBClass, they are left for application server implementation.
I have all this info from good tutorial at IBM's site http://www-106.ibm.com/developerworks/views/java/tutorials.jsp. Tutorial is called "Introduction to container-managed persistence and relationships
", Parts 1-4.