Defining a Simple Tag Handler 

Class: Example

package cwp.tags;

import javax.servlet.jsp.*;

import javax.servlet.jsp.tagext.*;

import java.io.*;

import java.math.*;

import cwp.*;

public class SimplePrimeTag

extends TagSupport

{

protected int len = 50;

public int 

doStartTag

() {

try {

JspWriter out = pageContext.getOut();

BigInteger prime = 

Primes.nextPrime(Primes.random(len));

out.print(prime);

} catch(IOException ioe) {

System.out.println("Error generating prime: " + ioe);

}

return(SKIP_BODY);

}}

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Defining a Simple Tag Library 

Descriptor

Start with XML header and DOCTYPE

Top level element is

taglib

Each tag defined by tag element containing:

name, whose body defines the base tag name. 

In this case, I use 

simplePrime

tagclass, which gives the fully qualified class name of the 

tag handler. In this case, I use 

cwp.tags.SimplePrimeTag

bodycontent, which gives hints to development 

environments. Optional. 

info, which gives a short description. Here, I use

Outputs a random 50 digit prime.

82

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