Patterns: Implementing Self-Service in an SOA Environment

104 Patterns: Implementing Self-Service in an SOA Environment

6.2.1 Web-based clients

In this section we discuss the key technologies involved with Web-based clients.

Web browser

A Web browser is a fundamental component of the Web client. For PC-based

clients, the browser typically incorporates support for HTML, DHTML, JavaScript,

and Java. Some browsers are beginning to add support for XML as well. Under

user control, there is a whole range of additional technologies that can be

configured as plug-ins, such as RealPlayer from RealNetworks or Macromedia

Flash.

As an application designer, you must consider the level of technology you can

assume will be available in the user’s browser, or you can add logic to your

application to enable slight modifications based upon the browser level. For

Internet users, this is especially true. With intranet users, you can assume

support for a standard browser. Regarding plug-ins, you need to consider what

portion of your intended user community will have that capability.

Cross-browser strategies are required to ensure robust application development.

Although many of these technology choices are maturing, they continue to be

inconsistently supported by the full range of browser vendors. Developers must

know browser compatibility for all features being exploited by the application. In

general, developers will need to code to a lowest denominator, or at least be able

to distinguish among browser types using programmatic techniques. The key

decision here is to determine the application requirements and behavior when

handled by old browsers, other platforms such as Linux® and Mac, and even the

latest browsers.

In the J2EE model, the Web browser plays the role of client container. The model

requires that the container provide a Java Runtime Environment as defined by

the Java 2 Platform, Standard Edition (J2SE). However, for an e-business

application that is to be accessed by the broadest set of users with varying

browser capabilities, the client is often written in HTML with no other

technologies. On an exception basis, limited use of other technologies, such as

using JavaScript for simple edit checks, can then be considered based on the

value to the user and the policy of the organization for whom the project is being

developed.

The emergence of pervasive devices introduces new considerations to your

design with regard to the content streams that the device can render and the

more limited capabilities of the browser. For example, Wireless Application

Protocol (WAP) enabled devices render content sent in Wireless Markup

Language (WML).