The J2EE specification (version 1.3) describes a set of technologies designed to address the presentation, business logic, and persistent storage needs of n-tier applications. Generally speaking, a J2EE environment consists of several types of components that communicate with each other and a persistent storage device (a database). There are four categories of components:
Java applets, which typically execute in a Web browser on a client machine
Java applications, which execute on a local or remote client machine
Java servlets, JavaServer Pages (JSPs), filters, and Web event listeners, which execute on a server machine
Enterprise JavaBeans (EJBs), which are application objects that execute on a server machine
Each of ...