What Is an EJB?
In a typical J2EE application, Enterprise JavaBeans (EJBs) contain the application's business logic and live business data. Although it is possible to use standard Java objects to contain your business logic and business data, using EJBs addresses many of the issues of using simple Java objects, such as scalability, lifecycle management, and state management.
Beans, Clients, Containers, and Servers
An EJB is essentially a managed middleware component that is created, controlled, and destroyed by the J2EE container in which it lives. This control allows the container to manage the number of EJBs currently in existence and the resources they are using, such as memory and database connections.
Each container will maintain a pool ...