JavaServer Pages, 3rd Edition

Chapter 6. Using JavaBeans Components in JSP Pages

The JavaBeans specification defines a set of programming conventions for Java classes that are used as pluggable components. In layman’s terms, tools that have no inside information about a class can use it if it’s developed according to these conventions. For instance, a generic GUI builder tool can support any widgets developed as JavaBeans components. A JavaBeans component, or just a bean for short, is often used in JSP as the container for the dynamic content to be displayed by a web page. It typically represents something specific, such as a person, a product, or a shopping order. When JSP is combined with servlets, the bean can be created and initialized with data by the servlet and passed to a JSP page that simply adds the bean’s data to the response. But even in a pure JSP application, a bean is a useful tool, for instance for capturing and validating user input.

A programmer must develop the bean, but someone who doesn’t have any programming experience can then use it in a JSP page. JSP defines a number of standard actions for working with beans, and the JSP Expression Language accepts beans as variables in expressions. In this chapter, we take a closer look at what a bean is and how it can produce dynamic content in a page. We’ll return to beans in Chapter 8 to see how they can be used for input validation.