We can iterate the body content of any tag using the doAfterBody()method of IterationTag interface.

Here we are going to use the TagSupport class which implements the IterationTag interface. For iterating the body content, we need to use the EVAL_BODY_AGAIN constant in the doAfterBody() method.

Example of Iteration using JSP Custom Tag

In this example, we are going to use the attribute in the custom tag, which returns the power of any given number. We have created three files here

  • index.jsp
  • PowerNumber.java
  • mytags.tld

index.jsp

<%@ taglib uri="WEB-INF/mytags.tld" prefix="m" %>  
  
3 ^ 5 =   
body

PowerNumber.java

package com.javatpoint.taghandler;  
  
import javax.servlet.jsp.JspException;  
import javax.servlet.jsp.JspWriter;  
import javax.servlet.jsp.tagext.TagSupport;  
  
public class PowerNumber extends TagSupport{  
private int number;  
private int power;  
private static int counter;  
private static int result=1;  
  
public void setPower(int power) {  
    this.power = power;  
}  
  
public void setNumber(int number) {  
    this.number = number;  
}  
  
public int doStartTag() throws JspException {  
    return EVAL_BODY_INCLUDE;  
}  
  
public int doAfterBody() {  
    counter++;   
    result *= number;   
    if (counter==power)   
      return SKIP_BODY;   
    else   
      return EVAL_BODY_AGAIN;   
  }   
  
public int doEndTag() throws JspException {  
    JspWriter out=pageContext.getOut();  
    try{  
        out.print(result);  
    }catch(Exception e){e.printStackTrace();}  
      
    return EVAL_PAGE;  
}  
}

mytags.tld

  
  
  
  
  1.0  
  1.2  
  simple  
  http://tomcat.apache.org/example-taglib  
  A simple tab library for the examples  
  
    
    power  
    com.javatpoint.taghandler.PowerNumber  
      
      
    number  
    true  
      
      
      
    power  
    true

Looping using Iteration Tag (creating tag for loop)

Let’s create a loop tag that iterates the body content of this tag.

File: index.jsp
  
  
  
Insert title here  
  
  
  
<%@taglib prefix="m" uri="sssuri" %>

My Name is khan

 

File: mytags.tld

  
  
  
  1.0  
  1.2  
  abc  
    
  sssuri  
   
    loop  
    com.javatpoint.customtag.Loop  
     
      
    start  
    true  
      
      
      
    end  
    true

File: Loop.java

package com.javatpoint.customtag;  
import javax.servlet.jsp.JspException;  
import javax.servlet.jsp.tagext.TagSupport;  
  
public class Loop extends TagSupport{  
    private int start=0;  
    private int end=0;  
      
    public void setStart(int start) {  
        this.start = start;  
    }  
    public void setEnd(int end) {  
        this.end = end;  
    }  
      
    @Override  
    public int doStartTag() throws JspException {  
        return EVAL_BODY_INCLUDE;  
    }  
  
    @Override  
    public int doAfterBody() throws JspException {  
        if(start<end){  
            start++;  
            return EVAL_BODY_AGAIN;  
        }else{  
        return SKIP_BODY;  
       }  
          
    }  
  
      
}

File: web.xml

  
  
  
  
  
sssuri  
/WEB-INF/mytags.tld

Output

Iteration Tag in JSP