JavaServer Pages, 3rd Edition

Custom actions

A custom action can be developed by a programmer to extend the JSP language. The JSP Standard Tag Library (JSTL) actions are developed using the API defined by the JSP specification. Application-specific custom actions can also be developed using this API, such as the custom actions for adding cookies to a response and setting headers for no caching used in this book. The JSTL actions are described in Appendix B and all custom actions of a generic nature used in this book are described in Appendix E.

The general syntax for custom actions is the same as for the JSP standard actions: a start tag (optionally with attributes), a body, and an end tag. Other elements and template text can be nested in the body. Here’s an example:

<ora:ifUserInRole value="admin">
  Greetings Master, I hope your day has been pleasant.
</ora:ifUserInRole>

The tag library containing the custom actions must be declared by the taglib directive, assigning a prefix for the custom action elements (ora in this example), before a custom action can be used in a JSP page.