J2EE Tutorial-2 (Distributed Multitiered Applications)

The J2EE platform uses a multitiered distributed application model. Application logic is divided into components according to function, and the various application components that make up a J2EE application are installed on different machines depending on the tier in the multitiered J2EE environment to which the application component belongs. Figure 1-1 shows two multitiered J2EE applications divided into the tiers described in the following list. The J2EE application parts shown in Figure 1-1 are presented in J2EE Components.Client-tier components run on the client machine.

Web-tier components run on the J2EE server.

• Client-tier components run on the client machine.


• Web-tier components run on the J2EE server.


• Business-tier components run on the J2EE server.


• Enterprise information system (EIS)-tier software runs on the EIS server.

Although a J2EE application can consist of the three or four tiers shown in Figure 1-1, J2EE multitiered applications are generally considered to be three-tiered applications because they are distributed over three different locations: client machines, the J2EE server machine, and the database or legacy machines at the back end. Three-tiered applications that run in this way extend the standard two-tiered client and server model by placing a multithreaded application server between the client application and back-end storage.

Figure 1-1 Multitiered Applications