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

J2EE Tutorial -1 (overview)

Today, more and more developers want to write distributed transactional applications for the enterprise and leverage the speed, security, and reliability of server-side technology. If you are already working in this area, you know that in today’s fast-moving and demanding world of e-commerce and information technology, enterprise applications have to be designed, built, and produced for less money, with greater speed, and with fewer resources than ever before.

To reduce costs and fast-track enterprise application design and development, the Java 2 Platform, Enterprise Edition (J2EE) technology provides a component-based approach to the design, development, assembly, and deployment of enterprise applications. The J2EE platform offers a multitiered distributed application model, the ability to reuse components, integratedExtensible Markup Language (XML)-based data interchange, a unified security model, and flexible transaction control. Not only can you deliver innovative customer solutions to market faster than ever, but your platform-independent J2EE component-based solutions are not tied to the products and application programming interfaces (APIs) of any one vendor. Vendors and customers enjoy the freedom to choose the products and components that best meet their business and technological requirements.

This tutorial takes an examples-based approach to describing the features and functionalities available in J2EE Software Development Kit (SDK) version 1.3. Whether you are a new or an experienced enterprise developer, you should find the examples and accompanying text a valuable and accessible knowledge base for creating your own enterprise solutions.

If you are new to J2EE applications development, this chapter is a good place to start. Here you will learn the J2EE architecture, become acquainted with important terms and concepts, and find out how to approach J2EE application programming, assembly, and deployment.