jakarta.el.ELException: Cannot convert [1.0] of type [class java.lang.String] to [class java.lang.Long]

I am trying to pass a parameter to a jsp:include. Then I use that parameter in a if statement, here is the jsps:

 <jsp:include page="/Review Score Display.jsp">
      <jsp:param name="Score" value="${reviewScore}"/>
 </jsp:include>

This is Review Score Display:

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<body>
<c:choose>
  <c:when test="${param.Score ge 1}">
    <span class="fa fa-star checked fa-2x"></span>
  </c:when>
  <c:otherwise>
    <span class="fa fa-star fa-2x"></span>
  </c:otherwise>
</c:choose>
<c:choose>
  <c:when test="${param.Score ge 2}">
    <span class="fa fa-star checked fa-2x"></span>
  </c:when>
  <c:otherwise>
    <span class="fa fa-star fa-2x"></span>
  </c:otherwise>
</c:choose>
<c:choose>
  <c:when test="${param.Score ge 3}">
    <span class="fa fa-star checked fa-2x"></span>
  </c:when>
  <c:otherwise>
    <span class="fa fa-star fa-2x"></span>
  </c:otherwise>
</c:choose>
</body>
</html>

But when I run it, I get an error page that indicates an error at line 13 of Review Score Display (the first c:when statement) saying jakarta.el.ELException: Cannot convert [1.0] of type [class java.lang.String] to [class java.lang.Long]

I'm not sure why the Score parameter is considered a string. If I do this: <c:when test="${reviewScore ge 1}"> in the original JSP, it works just fine, so I guess when I pass review score as a parameter in the jsp:include it gets converted into a string?

What can I do to make the comparison work?

Solution

When you pass a value using <jsp:param>, it becomes a string inside ${param.Score} - even if the original value was a number

Then, when JSTL's <c:when> tries to compare it like ${param.Score ge 1}, it expects a number, not a string. Since the value is still a string, it throws an error.

To fix this, you can pass the value as a request attribute instead of a param. In the parent JSP, set the attribute before including:

<%
    int score = Integer.parseInt(request.getParameter("reviewScore"));
    request.setAttribute("score", score);
%>

In "Review Score Display.jsp", just use:

<c:when test="${score ge 1}">

Besides setting a request attribute manually, there are a few other options - though most are less clean.

You could parse param.Score using a scriptlet and store it in a new attribute, but mixing scriptlets with JSTL isn't ideal. A better way is to pass the numeric value from your controller directly as a request attribute, avoiding <jsp:param> entirely.

It's also technically possible to coerce a string to a number using ${param.Score + 0 ge 1}, but this relies on implicit type conversion and can easily break if the parameter is empty or non-numeric.

If you want to keep your logic inside JSTL and avoid scriptlets, another option is to define your own custom EL function like parseInt(...). Create a static utility class:

package my.tags;

public class MyFunctions {
    public static int parseInt(String value) {
        return Integer.parseInt(value);
    }
}

Create a TLD file (e.g., my-functions.tld in WEB-INF):

<?xml version="1.0" encoding="UTF-8"?>
<taglib xmlns="http://java.sun.com/xml/ns/javaee"
        version="2.1">
    <tlib-version>1.0</tlib-version>
    <short-name>myfn</short-name>
    <uri>http://example.com/myfn</uri>

    <function>
        <name>parseInt</name>
        <function-class>my.tags.MyFunctions</function-class>
        <function-signature>int parseInt(java.lang.String)</function-signature>
    </function>
</taglib>

Use it in your JSP:

<%@ taglib prefix="myfn" uri="http://example.com/myfn" %>

<c:when test="${myfn:parseInt(param.Score) ge 1}">
  <!-- markup -->
</c:when>

This gives you a clean and reusable way to handle string-to-number conversion in JSP. Just make sure the .tld file is placed in WEB-INF and properly registered.