Preface

Until recently, JavaServer Pages (JSP) has, for the most part, been accessible only to Java developers. That's because JSP did not provide a standard set of tags for common functionality or a scripting language for page authors. The lack of those essential features meant that JSP developers had to embed Java code in JSP pages or implement custom tags that encapsulated that Java code. Either way, they had to be well versed in the Java programming language to effectively use JSP.

To implement maintainable and extensible Web applications, developers must decouple business and presentation logic. Without an expression language or standard tag library, JSP pages often contained a great deal of Java code, which allowed easy access to business logic. That Java code and the inevitable related business logic tightly coupled JSP pages with the underlying data model, which resulted in brittle systems that were difficult to modify or extend.

The JSP Standard Tag Library (JSTL) provides a scripting language and set of standard tags that make JSP accessible to page authors and make it much easier to separate business and presentation logic. Those benefits allow page authors to focus on a Web application's presentation, while Java developers implement business logic, which in turn makes those applications much easier to implement, maintain, and extend. Because JSTL has such a profound effect on the development of Java-based Web applications as a whole, it is one of the most important new developments for server-side Java.