Chapter 4: Building Presentation Logic with WebSphere Studio

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Overview

In previous chapters we have seen a description of the multi-tier and web based computing architecture supported by WebSphere and its correlation to the J2EE programming model. We have also seen that the programming model supports various clients types, including web browsers and pervasive devices. This chapter will discuss WebSphere's support for building a presentations layer for the web browser client using WebSphere Studio tooling:

• Tier-0 web browsers are the most ubiquitous presentation style used for J2EE applications. Presentation is handled by logic running in the Web Application Server and rendered by the browser. This pattern is useful because it localizes the presentation logic on the server. Distribution and management of a client application is almost a non-issue. Unfortunately, differences in browsers have sometimes forced the presentation logic on the server to be aware of the actual browser in use by the client. The focus of this chapter will be on building web application presentation logic.

• Tier-1 clients are commonly used for intranet computing environments. These applications provide a richer set of presentation features, but also tend to rely on direct communication with the business logic, using protocols such as IIOP. This direct communication requirement tends to place their use cases within an enterprise's firewall. A variety of libraries are available for implementing tier-1 client presentations, including the Standard Wideget Toolkit (SWT) (http://www.eclipse.org/articles/Article-SWT-Design-1/SWT-Design-1.html) and JFC/Swing components (http://java.sun.com/products/jfc/).

• Pervasive devices are just starting to become an important client for e-business applications. This type of client often has different display characteristics from a web browser on a desktop computer. WebSphere Application Server provides a servlet extension that allows us to detect the client device type and thus select a presentation specific to the device. In addition, WebSphere Everyplace Access provides several transcoding technologies that dynamically convert a single page definition to one appropriate for the client device.

The focus of this chapter is to illustrate how to use WebSphere to build and manage the execution of presentation logic. To illustrate this, we'll build the Plants-By-WebSphere application's web tier using WebSphere Studio tools and discuss the implications of running that application on the WebSphere Application Server.