11.9 Customized Tag Libraries

• Customized tags are used like standard XML tags.

  <prefix:tag attributes > body </prefix:tag>

• Tag libraries are loaded with directives of the following form.

  <%@ taglib prefix="prefix" [tagdir | uri]="..." %>

  <..UseTag.jsp..>

   <%@ taglib uri="abc" prefix="x" %>
   
   <x:foo name="..." value="..." >
   ...
   </x:foo>

  -_-_-
• A tag definition requires a declaration in a tag library descriptor and a tag handler
• A tag library descriptor (TLD) should satisfy the http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd DTD and be similar to
   
   <!DOCTYPE taglib PUBLIC
       "-//Sun Microsystems, Inc. //DTD JSP Tag Library 1.1//EN"
       "web-jsptaglib_1_1.dtd">
   <taglib>
     <tlibversion>...</tlibversion>
     <jspversion>...</jspversion>
     <shortname>...</shortname>
     <info>...</info>
     <tag>
       <name>...</name>
       <tagclass>...</tagclass>
       <attribute>
         <name>...</name>
       </attribute>
       .......
     </tag>
     .......
   </taglib>

  The tagclass element ponits to the location of the tag handler.

• The tag handler implements methods of the following classes.

  javax.servlet.jsp.tagext.Tag
  int doEndTag()	Process the end tag for this instance.
  int doStartTag()	Process the start tag for this instance.
  Tag getParent()	Get the parent (closest enclosing tag handler) for this tag handler.
  void release()	Called on a Tag handler to release state.
  	void setPageContext(PageContext pc) Set the current page context.
  void setParent(Tag t)	Set the parent (closest enclosing tag handler) of this tag handler.
  javax.servlet.jsp.tagext.BodyTag
  void doInitBody()	Prepare for evaluation of the body
  void setBodyContent(BodyContent b)	Set the bodyContent property

   
   import java.util.*;
   import javax.servlet.jsp.*;
   import javax.servlet.jsp.tagext.*;
   
   public class DefinitionTag extends TagSupport {
   
      public DefinitionTag() {
        ....
      }
      public int doStartTag() {
        ....
      }
      public int doEndTag()throws JspTagException {
        ....
      }
      public void release() {
        ....
   }  }