JavaServer Pages, Second Edition

Packaging and Installing a Tag Library

There are basically two ways the files that make up a tag library (the TLD and all the class files) can be made available to a container: packaged in a JAR file or kept as regular files in the filesystem. On top of this, there are three ways to identify the tag library you use in a JSP page. Let’s look at the two topics one at a time.

Making the Tag Library Files Available to the Container

During development, you may want to let the tag library classes and the TLD file reside as-is in the filesystem, since it makes it easy to change the TLD and modify and recompile the classes. Just make sure the class files are stored in a directory that’s part of the classpath for the JSP container, such as the WEB-INF/classes directory for the web application. The TLD must be also available as a file with a .tld extension in a directory where the JSP container can find it. The recommended location is the WEB-INF/tlds directory.

When you’re done with the development, you may want to package all tag-handler classes and the TLD in a JAR file. This makes it easier to install the library in an application. In this case, the TLD must be placed as a file with a .tld extension in the META-INF directory in the JAR file, for instance as META-INF/taglib.tld.

To create the JAR file, first arrange the files in a directory with a structure like this:

META-INF/
  taglib.tld
com/
  ora/
    jsp/
      tags/
        ForwardTag.class
        ...
      util/
        StringFormat.class
        ...

The structure for the class ...