The Java EE 5 Tutorial (PDF) - Oracle Software Downloads

Including theTag Library Implementation
In addition to declaring the tag library, you also must make the tag library implementation
available to the web application. There are several ways to do this. Tag library implementations
can be included in a WAR in an unpacked format: Tag files are packaged in the /WEB-INF/tag/
directory, and tag handler classes are packaged in the /WEB-INF/classes/ directory of the
WAR. Tag libraries already packaged into a JAR file are included in the /WEB-INF/lib/
directory of the WAR. Finally, an application server can load a tag library into all the web
applications running on the server. For example, in the Application Server, the JSTL TLDs and
libraries are distributed in the archive appserv-jstl.jar in as-install/lib/. This library is
automatically loaded into the classpath of all web applications running on the Application
Server, so you don’t need to add it to your web application.
The iterator tag library is implemented with tag handlers. Therefore, its implementation
classes are packaged in the /WEB-INF/classes/ directory.
Reusing Content in JSP Pages
There are many mechanisms for reusing JSP content in a JSP page. Three mechanisms that can
be categorized as direct reuse are discussed here:
■ The include directive
■ Preludes and codas
■ The jsp:include element
An indirect method of content reuse occurs when a tag file is used to define a custom tag that is
used by many web applications. Tag files are discussed in the section “Encapsulating Reusable
Content Using Tag Files” on page 231 in Chapter 8, “Custom Tags in JSP Pages.”
The include directive is processed when the JSP page is translated into a servlet class. The effect
of the directive is to insert the text contained in another file (either static content or another JSP
page) into the including JSP page. You would probably use the include directive to include
banner content, copyright information, or any chunk of content that you might want to reuse in
another page. The syntax for the include directive is as follows:
For example, all the Duke’s Bookstore application pages could include the file banner.jspf,
which contains the banner content, by using the following directive:
Reusing Content in JSP Pages
Another way to do a static include is to use the prelude and coda mechanisms described in
“Defining Implicit Includes” on page 179. This is the approach used by the Duke’s Bookstore
application.
Chapter 5 • JavaServer PagesTechnology 173