How can I do sth like this ${requestScope.list.size} ?

Question

Hi, I have 2 attributes which I pass like this
requsest.setAttribute("startPoint", 3);
request.setAttribute("myList", myList);
where myList is a ArrayList filld with objects. On jsp page I want to count 2 values first and last number:
<c:set var="firstNumber" value="${requestScope.startPoint+1}"/> - this works fine.
<c:set var="lastNumber" value="${requestScope.startPoint+requestScope.myList.size}"/> - this is impropper.
How can I use as integer size of list which is passed as request attribute. Is this possible?
I would appreciate any hepl.

Answer 1

Hang on. For such things you can build your own EL functions - it is very easy and involves only 4 steps.
1. Write a class containing a method (must be static) to calculate size of any list.
[Put the class in /WEB-INF/classes, so your file will reside as /WEB-INF/classes/myfunctions/MyFunctions.class]
package myfunctions;
import java.util.List;
public class MyFunctions{
     public static int getListSize(List list){
          return list==null?0:list.size();
}2. In your taglib add an entry (in case you don't have already create one) for the EL function:
[Say our taglib is mytags.tld in /WEB-INF]
<taglib 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-jsptaglibrary_2_0.xsd"
     version="2.0">
     <tlib-version>1.0</tlib-version>
     <short-name>MyTagLib</short-name>
     <function>
          <description>List Size</description>
          <name>size</name>
          <function-class>myfunctions.MyFunctions</function-class>
          <function-signature>int getListSize(java.util.List)</function-signature>
     </function>
</taglib>3. Now in your JSP add following line to use your new EL function:
<%@taglib uri="/WEB-INF/mytags.tld" prefix="mt"%>4. And use as:
<input type=text value="${mt:size(requestScope.myList)}" />Note that there no issues using JSTL EL functions. My intention is to resolve your problem and at the same time to give you a glance how to write and use your own EL functions (might be useful in future).
Thanks,
Mrityunjoy