Core Servlets and JavaServer Pages™

A.14. Creating Custom JSP Tag Libraries

The Tag Handler Class

• Implement Tag interface by extending TagSupport (no tag body or tag body included verbatim) or BodyTagSupport (tag body is manipulated).

• doStartTag: code to run at beginning of tag

• doEndTag: code to run at end of tag

• doAfterBody: code to process tag body

The Tag Library Descriptor File

• Within taglib element, contains tag element for each tag handler. E.g.:

  <tag>
    <name>prime</name>
    <tagclass>coreservlets.tags.PrimeTag</tagclass>
    <info>Outputs a random N-digit prime.</info>
    <bodycontent>EMPTY</bodycontent>
    <attribute>
      <name>length</name>
      <required>false</required>
    </attribute>
  </tag>
  

The JSP File

• <%@ taglib uri="some-taglib.tld" prefix="prefix" %>

• <prefix:tagname />

• <prefix:tagname>body</prefix:tagname> ...