Java 2, Enterprise Edition (J2EE)

Integrated, open standards-based portable platform for development of scalable enterprise applications.

Open Standards EJB, JSP, Servlets, JDBC, JNDI, RMI construct the Enterprise Java platform.
Portability These technologies support the Java tenet: "Write Once, Run Anywhere" (WORA). Moving the scripting to the server allows developers to make changes at a distance and quickly see the effects on the application without the inconvenience of recompiling.
Scalability Enterprise application systems support high scalability by using a multitier, distributed application architecture. In a multitier architecture, the client application contains only presentation logic--a thin client.
Components
The presentation logic, business logic, and data access logic are partitioned into separate components and deployed on one or more servers, which allows an application to take advantage of the power of multithreaded and multiprocessing systems.

Other Advantages of Java Enterprise Platform

Language and API experiences garnered from one area of the platform can be leveraged when dealing with another area. For example, experience of writing a Java applet is directly applicable to writing a servlet. Experience of writing a servlet can help when writing your first EJB, or vice versa.

Sandbox, Garbage Collection, and Exception Handling automatically reduce the problem of one component interfering with the operation of the server or another component. For example, servlets allow plugging custom code into a Web server as a plug-in or extension library would. However, servlets have garbage collection and exception handling capabilities, so a problem in a servlet should not affect the server as a whole. The same is true for EJBs that can be deployed on a database or application server.