Tag libraries must follow important conventions for initializing tag fields. The JSP specification lets a JSP container, like Resin, reuse tag handler instances for efficiency and performance. Because this optimization restricts how tags can use fields, even experienced developers will benefit from this tutorial.

The simplest kind of tag does not evaluate it's contents.

Tags become more useful once you add attributes. This example creates a ct:href tag.

Body tags can grab JSP results and send them to an entirely different location. It's easy to create a custom tag that sends part of a JSP to a survey account. The required attribute to will specify the mail address for the mail and subject specifies the subject. The enclosed JSP contains the body of the mail.

JSP 2.0 introduces XML-based tag files. Instead of having to write Java code for custom tags, applications can use XML or JSP syntax for their tags. Tag files do not require .tld files, making development simpler.