Tag Libraries in JSP

By: Sathya Narayana Viewed: 153241 times  Printer Friendly Format    


The syntax for using tag libraries is similar to that for the standard actions except of course that the tag names and attributes are defined in the tag library itself rather than by the JSP standard. Each tag library is associated with a prefix by using the taglib directive to map the prefix to a URI identifying the tag library. For example, using the Jakarta Taglibs project's request tag library (http://jakarta.apache.org/taglibs/doc/request-doc/intro.html) looks like this:

<%@ taglib uri="http://jakarta.apache.org/taglibs/request-1.0" prefix="req"
%>
Within the JSP, you can then use tags from the library by using the prefix defined in the taglib directive and the tag's name. For example:

<req:attributes id="loop">
Name: <jsp:getProperty name="loop" property="name"/>
Value: <jsp:getProperty name="loop" property="value"/>
</req:attributes>

You can set up the mapping between a particular URI (as used in the taglib directive) and the tag library descriptor in one of two ways. In JSP, it's possible to package tag libraries so that the mapping is automatic, based on settings contained in the tag library descriptor file. Alternatively, you can make an entry in the web.xml file to map a URI to a tag library descriptor file:

<taglib>
<taglib-uri>http://jakarta.apache.org/taglibs/request-1.0</taglib-uri>
<taglib-location>/WEB-INF/request.tld</taglib-location>
</taglib>



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