Java Enterprise in a Nutshell, Second Edition

JSP Actions

If you’ve spent any time working with servlets, our examples up to this point really haven’t been anything new. Essentially, we’ve replaced reams of println( ) calls with template text in a JSP. This certainly saves time, but we aren’t doing anything different. For one thing, at the beginning of this chapter, we promised that JSP allowed nonprogramming web designers and content creators to help create dynamic content. The techniques we’ve just seen let you do that, but you have to teach them Java first, which pretty much defeats the purpose.

HTML developers may not be confident tackling server-side Java code (and, frankly, they probably shouldn’t be), but they’re certainly comfortable with markup tags. Web browsers, after all, just treat tags as instructions. If a browser sees a <b> tag, it turns the running text to boldface until it sees another </b> tag. Scriptlets in JSP do the same thing, except in two steps: the server processes the script, possibly producing more HTML, and the browser then views it. This is not a difficult concept, but we haven’t gotten around the fact that the first set of instructions are provided as Java code and hence require a Java programmer with some time on her hands.

JSP solves this problem with action tags. An action tag looks like a regular HTML tag, and doesn’t follow the <% %> syntax conventions we’ve seen before. JSP actions are divided into two categories: built-in functions, which we’ll discuss in this section, and custom tags, ...