Web Development with JavaServer Pages

JSP and Java 2 Enterprise Edition

JSP is now an integral part of developing web-based applications using Java. Because of its ability to separate presentation from implementation logic by combining standard markup text with scripting elements and object-oriented components, JSP provides an excellent front-end technology for applications that are deployed over the web.

Java platform editions

In June 1999, Sun Microsystems announced that the Java 2 software platform would be split into three editions, aimed at different categories of hardware deployment platforms. The traditional Java Runtime Environment, or JRE, which contains all of the core classes in the formal language specification (including, for example, the standard networking, utility, and graphical user interface classes), has been renamed the Java 2 Standard Edition, or J2SE. The J2SE is targeted toward traditional desktop computing platforms, such as Microsoft Windows and Apple Macintosh personal computers.

A subset of the core classes, targeted toward handheld devices (for example, PDAs- personal digital assistants- such as the 3Com PalmPilot), embedded processors (such as Internet-enabled toasters), and so-called "information appliances" (e. g., digital TV set-top boxes), comprises the Java 2 Micro Edition, or J2ME. The goal of J2ME is to provide a Java environment with minimal footprint, that nevertheless supports the Java vision of Write Once, Run Anywhere™ program code.

At the opposite extreme from J2ME is the Java 2 Enterprise Edition, or J2EE. Rather than subtract from the Java 2 core, as the micro edition does, J2EE bundles the core Java classes with extensions targeted toward enterprise application development. For example, J2EE includes support for Enterprise JavaBeans, which provides a set of standard abstractions for accessing corporate data stores, such as databases and directory servers, with automatic support for transaction management and resource pooling.

Given the inherent complexity involved in designing, constructing, and maintaining large-scale enterprise applications, however, Sun's specification of J2EE includes a set of guidelines for developing software using the J2EE platform. These guidelines take the form of a recommended base software architecture referred to as the J2EE Application Model.

Web-based applications

A key element of the J2EE Application Model is the use of the web as a preferred mechanism for data delivery between the application and the end user, relying on the web browser as a primary user interface for enterprise software. The advantage of this approach is that the web browser, in just the few short years since the birth of the World Wide Web, has been established as a ubiquitous, cross-platform,de facto standard for accessing data over the network. When an application relies on the web browser for its user interface, there is no need for end users to install any additional software to run the application. And as new versions of the application are developed and deployed on the server, end users automatically start using the new version: end users need not take any local action to upgrade to the latest version.

To facilitate web-based applications, then, both servlets and JSP are required elements of the J2EE specification. And while both technologies can be used to dynamically generate HTML to be sent to an end user's web browser, only JSP enforces a strong separation between the presentation logic involved in displaying data and the business or programming logic used to generate that data in the first place. This separation means that the design of the user interface, embodied in a set of JSP pages, can be carried out independently from the design of the other code that runs on the server (e. g., interpreting requests, formulating database queries, and manipulating results). This independence leads to much more robust applications, since changes to one part of the application generally do not require corresponding changes to other parts. Specifically, when using JSP, changes to the presentation of the data (e. g., formatting of the data, design of the associated graphics, overall page layout) do not require any changes to the underlying server code that supplied that data in the first place.

Given Sun's selection of servlets and JSPs as major components of J2EE, it is clear that support for these technologies will continue to grow. Even now, it is more the rule than the exception that enterprise web application servers, such as Netscape Application Server, IBM WebSphere, and BEA WebLogic, include support for both servlets and JSPs.

In addition to growth in the market for software to deploy JSP, it is anticipated that improved development tools will soon be available. Currently, JSP development is essentially a manual process, but several of the web authoring tool vendors have announced support for JavaServer Pages in upcoming releases of their products, including Drumbeat 2000 from Macromedia, IBM's Visual Age for Java, and HomeSite from Allaire. JSP's built-in support for component-based design using JavaBeans, discussed in a later section, promises to enable a new set of tools for creating dynamic web pages graphically, using a visual programming approach to drag and drop server-side Java components into WYSIWYG editing tools. The ability to create sophisticated JSP pages without ever seeing HTML tags, let alone Java code, may soon be a reality.

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