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JSP- Custom Tags

JSP Custom Tags

For creating any custom tag, we need to follow following steps:

  1. Create the Tag handler class (.java)

  2. Create the Tag Library Descriptor (TLD) file and define tags (.tld)

  3. Create the JSP file that uses the Custom tags (.JSP)


1.Create the Tag handler class (.java)

  • To create the Tag Handler, we are inheriting the TagSupport class

  • And override doStartTag().

  • To write data for the jsp, we need to use the JspWriter class.its like res.getWriter()

  • PageContext class provides getOut() method that returns JspWriter instance

  • These classes are not Default with servlet-api.we have to download jsp-api.jar

public class MyTag extends TagSupport{  

public int doStartTag() throws JspException 
{  
   	   JspWriter out=pageContext.getOut();//returns the instance of JspWriter  
    	   out.print(Calendar.getInstance().getTime());//printing date using JspWriter  
    	    return SKIP_BODY;//will not evaluate the body content of the tag  
}  
}

2.Create the Tag Library Descriptor (TLD) file and define tags(.tld)

Tag Library Descriptor (TLD) file contains information of tag and Tag Hander classes. It must be contained inside the WEB-INF directory.

mytag.tld
---------------------
<?xml version="1.0" encoding="ISO-8859-1" ?>  
<!DOCTYPE taglib  
        PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"  
    "http://java.sun.com/j2ee/dtd/web-jsptaglibrary_1_2.dtd">

<taglib>
	<tlib-version>1.0</tlib-version>
	<jsp-version>1.2</jsp-version>
	<short-name>simple</short-name>
	<uri>http://tomcat.apache.org/example-taglib</uri>
	<tag>
 <name>today</name>
 <tag-class>demo.MyTag</tag-class>
	</tag>
</taglib>

3.Create the JSP file that uses the Custom tags (.JSP)

DateJsp.jsp
-------------------
<%@ taglib uri="WEB-INF/mytag.tld" prefix="m" %>  
Current Date and Time is: <m:today/>

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