Using EL How to write a custom tag?

Question

I want to write a tag wich takes input and output as it is.Like when i pass an primitive types then it directly pass no transfer as we are puting "" literial to the values and pass it.
For Example:
<fun:add i1=10 i2=20 />
check my code as i write tld ,and classes
------ function.jsp ------
<%@ taglib uri="http://jakarta.apache.org/explang/funtion-taglib"
prefix="fun" %>
<%=<fun:add i1=10 i2=20 /> %>
----------function.tld-------------
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE taglib
PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
"http://java.sun.com/j2ee/dtd/web-jsptaglibrary_2_0.dtd">
<taglib>
<tlib-version>1.2</tlib-version>
<jsp-version>2</jsp-version>
<short-name>fun</short-name>
<tag>
<name>add</name>
<tag-class>exp.MyClass</tag-class>
<body-content>TAGDEPENDENT</body-content>
<resolver-class>exp.MyVarRes</resolver-class>
<expression-class>exp.MyExp</expression-class>
<attribute>
<name>i1</name>
<required>true</required>
</attribute>
<attribute>
<name>i2</name>
<required>true</required>
</attribute>
</tag>
</taglib>
---------evalutor&other classes-------
------MyClass.java-------
package explang;
public class MyClass{
public int add(int x,int y){
return(x+y);
--------MyExp----------------
package explang;
import javax.servlet.jsp.el.*;
public class MyExp extends Expression{
public Object evaluate(VariableResolver vr)throws ELException{
try{
System.out.println("Execute evalute on MyExp");
return Class.forName("java.lang.Integer.class");
}catch(Exception e){ return null;}
------------MyExpEval----------------------
package explang;
import javax.servlet.jsp.el.*;
public class MyExpEval extends ExpressionEvaluator{
private int i1,i2;
public void setI1(Integer i1){
this.i1=i1.intValue();
public void setI2(Integer i2){
this.i2=i2.intValue();
public java.lang.Object evaluate(java.lang.String name,java.lang.Class cls,javax.servlet.jsp.el.VariableResolver vr,javax.servlet.jsp.el.FunctionMapper fm)
throws ELException{
MyClass mc=new MyClass();
try{
mc=(MyClass)cls.newInstance();
}catch(Exception e){ }
int res=mc.add(i1,i2);
return new Integer(res);
public javax.servlet.jsp.el.Expression parseExpression(java.lang.String name,java.lang.Class cls,javax.servlet.jsp.el.FunctionMapper fm)
throws ELException{
return null;
------------MyVarRes------
package explang;
import javax.servlet.jsp.el.*;
import javax.servlet.jsp.PageContext;
public class MyVarRes implements VariableResolver{
private PageContext mCtx;
public MyVarRes(PageContext ctx){
System.out.println("Intialize the PageContext");
this.mCtx=ctx;
public Object resolveVariable(String pName )throws ELException{
if("pageContext".equals(pName))
return mCtx;
else
return mCtx.findAttribute(pName);
public Object resolveVariable(String name,Object gtype)throws ELException{
if(gtype instanceof java.lang.Long)
return (java.lang.Integer)gtype;
return null;
Is there any solution plz guide me,i have somewhere stuck in the middle bcz of this?

Answer 1

I want to write a tag wich takes input and output as
it is.Like when i pass an primitive types then it
directly pass no transfer as we are puting ""
literial to the values and pass it.
For Example:
<fun:add i1=10 i2=20 /> Can't do that, and even if you could, you shouldn't.
1: Correct XHTML syntax requires the quotes, and custom tags were designed to fit into XHTML syntax.
2: What would you possibly gain? doing <fun:add i1="10" i2="20" /> will translate the values to the appropriate data type for you - if you declare your set-method to have a Long prameter, then these values will be translated to Longs... Same for primitives...
check my code as i write tld ,and classes
------ function.jsp ------
<%@ taglib
uri="http://jakarta.apache.org/explang/funtion-taglib"
prefix="fun" %>
<%=<fun:add i1="10" i2="20" /> %>What are you trying to do here? You can't put a custom tag inside a scriptlet/expression like that. You would either use custom tags OR scriptlets, not both. After all, what goes between <% ... %> tags (and <%= ... %>) needs to be Java code. And <fun:add i1="10" i2="20"/> is not java code.