Preface

JavaServer Pages™ (JSP) is a technology for web application development that has received a great deal of attention since it was first announced in 1999. Since then, it has gone through three revisions. This book covers the 2.0 version of the specification.

Why is JSP so exciting? One reason is that JSP is Java-based, and Java™ is well suited for enterprise computing. In fact, JSP is a key part of the Java 2™ Enterprise Edition (J2EE) platform and can take advantage of the many Java Enterprise™ libraries, such as JDBC™, JNDI™, and Enterprise JavaBeans™.

Another reason is that JSP supports a powerful model for developing web applications that separates presentation from processing. Understanding why this is so important requires a bit of a history lesson. In the early days of the Web, the only tool for developing dynamic web content was the Common Gateway Interface (CGI). CGI outlined how a web server made user input available to a program, as well as how the program provided the web server with dynamically generated content to send back. CGI scripts were typically written in Perl. (In fact, Perl/CGI scripts still drive numerous dynamic web sites.) However, CGI is not an efficient solution. For every request, the web server has to create a new operating-system process, load a Perl interpreter and the Perl script, execute the script, and then dispose of it when it's done.

To provide a more efficient solution, various alternatives to CGI have been added to programmers' toolboxes over the last few years: FastCGI, for example, runs each CGI program in an external permanent process (or a pool of processes). In addition, mod_perl for Apache, NSAPI for Netscape, and ISAPI for Microsoft's IIS all run server-side programs in the same process as the web server itself. While these solutions offer better performance and scalability, each one is supported only by a subset of the popular web servers.

The Java Servlet API, introduced in early 1997, provides a solution to the portability issue. However, all these technologies suffer from a common problem: HTML code embedded inside programs. If you've ever looked at the code for a servlet, you've probably seen endless calls to out.println( ) that contain scores of HTML tags. For the individual developer working on a simple web site, this approach may work fine, but it makes it difficult for people with different skills to work together to develop a web application.

This embedded HTML code is becoming a significant problem. As web sites become increasingly complex and more critical to an organization's success, the appearance and usability of the web interface becomes paramount. New client technologies, such as client-side scripts and DHTML, are used to develop more responsive and interactive user interfaces, stylesheets can make it easier to globally change fonts and colors, and images make the interface more appealing. At the same time, server-side code is getting more complex, and the demands for reliability, performance, and fault tolerance are increasing. The increasing complexity of web applications requires a development model that allows people with different skills to cooperate efficiently.

JSP provides just such a development model, allowing web page authors with skills in areas such as client-side technologies and usability to work in tandem with programmers who are experienced in server-side technologies, such as multithreading, resource pooling, databases, and caching. While there are other technologies, such as ASP, PHP, and ColdFusion, that support similar development models, none offer all the advantages of JSP.