Declaring a Custom Tag Library

As you know by now, a JSP page contains a mixture of JSP elements and template text, in which the template text can be HTML or XML elements. The JSP container needs to figure out which is which. It’s easy for it to recognize the standard JSP elements (because they all use the jsp namespace prefix), but it needs some help to find which elements represent custom actions. That’s where the tag library declaration comes into play.

Example 7-1 shows a page that uses a custom action from a custom tag library.

Example 7-1. Custom tag library declaration (message.jsp) 

<%@ page contentType="text/html" %>
<%@ taglib prefix="ora" uri="orataglib" %>
<html>
  <head>
    <title>Messages of the Day</title>
  </head>
  <body bgcolor="white">
    <h1>Messages of the Day</h1>
    <h2>Deep Thoughts - by Jack Handey</h2>
    <i>
      <ora:motd category="thoughts" />
    </i>
  
    <h2>Quotes From the Famous and the Unknown</h2>
    <i>
      <ora:motd category="quotes" />
    </i>
  </body>
</html>

This page displays messages from the same collections as the examples in Chapter 6. The second directive in Example 7-1 is a taglib directive, which is used to declare a custom tag library. Now, let’s see what this really means. In order for the JSP container to use actions from a tag library, it must be able to do two things: recognize that an element represents a custom action from a specific library and find the Java class that implements the custom action logic.

The first requirement -- figuring out which library an action ...

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