More Servlets and JavaServer Pages

Chapter 11: New Tag Library Features in JSP 1.2

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Source Code from Chapter

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Updates: Updated tag file examples can be found here (basics) and here (advanced). These examples have been updated to JSP 2.0, so the code is substantially different than in the rest of the More Servlets & JSP source code archive. The updated examples are bundled as MyEclipse projects, but can easily be used in regular Eclipse or without an IDE.
ActiveSessionCounter.java. Listener that keeps track of the number of sessions that the Web application is currently using.
SessionCountTag.java. Tag that prints out the number of active sessions.
SessionCountWarningTag.java. If the number of active sessions is above the limit, this tag prints a warning. Otherwise, it does nothing.
session-count-taglib-0.9-beta.tld. A tag library that lets you print out the number of sessions currently in memory and/or a warning about the session count exceeding the limit.

The tlib-version number and the TLD filename are intended to suggest that this tag library is in development. In such a situation, you want to use the web.xml taglib element to define an alias for the TLD filename. You would want to do so even if you weren't trying to accommodate Tomcat 4.0, which only reads listener declarations from TLD files that are declared that way.
web.xml. Deployment descriptor for Web application of this chapter.
index.jsp. Home page. Uses the custom tags.
test.jsp, make-sessions.html, and ColorUtils.java. Page and associated utilities that merely load multiple copies of the same JSP page. When used in a browser that has cookies disabled, it forces server to create 49 new sessions for each request.
SAXValidator.java. A "validator" that really just prints out an outline of the JSP page (in its XML representation). The validate method always returns null, so the page is always considered valid.
PrintHandler.java. A SAX handler that prints out the start tags, end tags, and first word of tag body. Indents two spaces for each nesting level.
OuterTag.java. Custom tag that prints out a simple message. A TagLibraryValidator will enforce a nesting order for tags associated with this class.
InnerTag.java. Custom tag that prints out a simple message. A TagLibraryValidator will enforce a nesting order for tags associated with this class.
NestingValidator.java. A validator that verifies that tags follow proper nesting order.
NestingHandler.java. A SAX handler that returns an exception if either of the following two situations occurs:
- The designated outer tag is directly or indirectly nested within the outer tag (i.e., itself).
- The designated inner tag is not directly or indirectly nested within the outer tag.
nested-tag-taglib.tld. TLD file for tag library that has two tags: outerTag and innerTag. A TagLibraryValidator will enforce the following nesting rules:
1. innerTag can only appear inside outerTag. It can be nested, however.
2. outerTag cannot be nested within other outerTag instances.
nesting-test1.jsp. Page with proper tag nesting order.
nesting-test2.jsp. Another page with proper tag nesting order.
nesting-test3.jsp. A page with improper tag nesting order.
nesting-test4.jsp. Another page with improper tag nesting order.
CatchTag.java. Tag that traces the life cycle of tags that implement the TryCatchFinally interface.
catch-tag-taglib.tld. TLD file for tag library that uses a simple tag to illustrate the behavior of the TryCatchFinally interface.
catchTest.jsp. Page that uses CatchTag. Requires the styles.css style sheet and the Utils class.
Utils.java. Class with a static method that sometimes throws an exception.
RepeatTag1.java. Tag that repeats the body the specified number of times. JSP 1.1 version.
repeat-taglib.tld. TLD file for tag library that has two tags: repeatTag1 and repeatTag2. These are JSP 1.1 and JSP 1.2 versions of simple looping tags.
repeat-test1.jsp. JSP page that uses
RepeatTag1.
RepeatTag2.java. Tag that repeats the body the specified number of times. JSP 1.2 version.
repeat-test2.jsp. JSP page that uses
RepeatTag2.
taglibs.war. The entire taglibs application bundled in a WAR (Web ARchive) file.