Support for custom actions (or custom tags) within JSP was introduced in the JSP 1.1 specification. This feature allows developers to extend the available tags beyond what JSP alone provides for. The custom tags are grouped together into tag libraries, which can be reused across applications.
The Struts framework takes advantage of the tag library feature of JSP to include several different categories of tags that help to make the presentation layer more manageable and reusable. Using the Struts custom tag libraries, developers are able to interact with the rest of the framework without including Java code in the JSP pages.
This chapter provides an overview of the different categories of tags available in the Struts framework and how they can make developing applications even easier. This chapter is not meant to be an exhaustive reference for every tag that's part of the Struts tag libraries—that information can be found within the Struts user guide or JavaDocs. The real purpose of this chapter is to put forth the benefits of using the Struts tag libraries and to provide a few strategies that can help make the switch to using the tags less painful.
Finally, this chapter will touch upon a new initiative going through the Java Community Process (JCP) that is intended to help standardize some of the more commonly used custom tags. This, in turn, will make applications built using these tags even more portable across containers and frameworks.