Prentice Hall and Sun Microsystems. Personal use only; do not redistribute.

Chapter

SP 1.1 introduced an extremely valuable new capability: the ability to

define your own JSP tags. You define how the tag, its attributes, and its

J

body are interpreted, then group your tags into collections called tag

libraries that can be used in any number of JSP files. The ability to

define tag libraries in this way permits Java developers to boil down complex

server side behaviors into simple and easy to use elements that content

developers can easily incorporate into their JSP pages. 

Custom tags accomplish some of the same goals as beans that are accessed

with 

jsp:useBean

 (see Chapter 13,  Using JavaBeans with JSP ) encapsu 

lating complex behaviors into simple and accessible forms. There are several

differences, however. First, beans cannot manipulate JSP content; custom

tags can. Second, complex operations can be reduced to a significantly sim 

pler form with custom tags than with beans. Third, custom tags require quite

a bit more work to set up than do beans. Fourth, beans are often defined in

one servlet and then used in a different servlet or JSP page (see Chapter 15,

 Integrating Servlets and JSP ), whereas custom tags usually define more

self contained behavior. Finally, custom tags are available only in JSP 1.1, but

beans can be used in both JSP 1.0 and 1.1.

At the time this book went to press, no official release of Tomcat 3.0 prop 

erly supported custom tags, so the examples in this chapter use the beta ver 

sion of Tomcat 3.1. Other than the support for custom tags and a few

efficiency improvements and minor bug fixes, there is little difference in the

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