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9. Using JSTL: Custom tags are powerful

Chapter 9. Using JSTL: Custom tags are powerful

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Sometimes you need more than EL or standard actions. What if you want to loop through the data in an array, and display one item per row in an HTML table? You know you could write that in two seconds using a for loop in a scriptlet. But you’re trying to get away from scripting. No problem. When EL and standard actions aren’t enough, you can use custom tags. They’re as easy to use in a JSP as standard actions. Even better, someone’s already written a pile of the ones you’re most likely to need, and bundled them into the JSP Standard Tag Library (JSTL). In this chapter we’ll learn to use custom tags, and in the next chapter we’ll learn to create our own.

OBJECTIVES

Building JSP pages using tag libraries

9.1

Describe the syntax and semantics of the ‘taglib’ directive: for a standard tag library, for a library of Tag Files.

9.2

Given a design goal, create the custom tag structure to support that goal.

9.3

Identify the tag syntax and describe the action semantics of the following JSP Standard Tag Library (JSTL v1.1) tags: (a) core tags: out, set, remove, and catch, (b) conditional tags: if, choose, when, and otherwise, (c) iteration tags: forEach, and (d) URL-related: url.

Coverage Notes:

All of the objectives in this section are covered in this chapter, although some of the content is covered again in the next chapter (Developing Custom Tags).

Note

Installing the JSTL 1.1

The JSTL 1.1 is NOT part of the JSP 2.0 specification! Having access to the Servlet and JSP APIs doesn’t mean you have access to JSTL.

Before you can use JSTL, you need to put two files, “jstl.jar” and “standard.jar” into the WEB-INF/lib directory of your web app. That means each web app needs a copy.

In Tomcat 5, the two files are already in the example applications that ship out-of-the-box with Tomcat, so all you need to do is copy them from one directory and put them into your own app’s WEB-INF/lib directory.

Copy the files from the Tomcat examples at:

webapps/jsp-examples/WEB-INF/lib/jstl.jar

webapps/jsp-examples/WEB-INF/ lib/standard.jar

And place it in your own web app’s WEB-INF/lib directory.

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