Taglibrary example| Custom tags


	JAVA

Tag Support class
example of a tag library

There four steps to do a simple counter example in making use of custom tag libraries.

1) Create a Class which extends TagSupport.

please see the below code for the counter example. class name: CounterTag

package jstl; import java.io.IOException; import javax.servlet.jsp.JspException; import javax.servlet.jsp.tagext.TagSupport; public class CounterTag extends TagSupport { int counter = 0; @Override public int doStartTag() throws JspException { try { pageContext.getOut().write(getCounter()+""); } catch (IOException e) { throw new JspException("Counter has not been populates propely"); } return SKIP_BODY; } private int getCounter() { return counter++; } }

step no 2)

in WEB-INF directory of tomcat create a directory calleds tlds and

make a file with the following code file name "counter.tld"

<?xml version="1.0" encoding="ISO-8859-1" ?> <!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd"> <taglib> <tlibversion>1.0</tlibversion> <jspversion>1.1</jspversion> <shortname>counter</shortname> <info>Counter example in tag lib custom</info>  <tag> <name>counter</name> <tagclass>jstl.CounterTag</tagclass> <bodycontent>empty</bodycontent> <info> This is a simple hello tag. </info> </tag> </taglib>

Step number 3 entry in web.xml file

file name web.xml( web.xml file resides in your tomcat in WEB-INF, just modify or paste the folowing code

<?xml version="1.0" encoding="UTF-8"?> <web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_3.xsd"> <display-name> JSTlExpressions</display-name> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> <welcome-file>default.html</welcome-file> <welcome-file>default.htm</welcome-file> <welcome-file>default.jsp</welcome-file> </welcome-file-list> <taglib> <taglib-uri>/counter</taglib-uri> <taglib-location>/WEB-INF/tlds/counter.tld</taglib-location> </taglib> </web-app>

Step number 4 make a JSP page any name would be fine

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <%@ taglib uri="/counter" prefix="counter" %> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Insert title here</title> </head> <body> Number of times visited <counter:counter/> </body> </html>

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