Ternary operator in JSTL/EL

Question

The following tag of JSTL can be used to set a value to a variable in a request scope.

<c:set var="value" scope="request" value="someValue"/> 

I want to check conditionally, if the variable value being set is empty or not and display the result accordingly something like the following, using <c:when>...</c:when>.

<c:choose>     <c:when test="${not empty value}">         <c:out default="None" value="${value}"/>     </c:when>     <c:otherwise>         <c:out default="None" value="None"/>     </c:otherwise> </c:choose> 

I want to reduce the line of code using a ternary expression like,

<c:out default="None" value="${not empty value ? value : 'None'}"/> 

It is evaluated as it actually means but if I interchange the order of the expressions like,

<c:out default="None" value="${empty value ? 'None' : value}"/> 

then it is a syntax error indicating,

"${empty value?'None':value}" contains invalid expression(s): javax.el.ELException: Error Parsing: ${empty value?'None':value}

So why does this happen?

---

I'm using the JSTL 1.1 library and the following taglib is included,

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

Answer 1

I tested the following page in Tomcat 5.59, JSP 2.0 and JSTL 1.1. It ran without any errors.

<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>  <c:set var="value" scope="request" value="someValue"/> <c:out default="None" escapeXml="true" value="${not empty value ? value : 'None'}" /> <c:out default="None" escapeXml="true" value="${empty value ? 'None' : value}" /> <c:set var="value" scope="request" value="" /> <br/> <c:out default="None" escapeXml="true" value="${not empty value ? value : 'None'}" /> <c:out default="None" escapeXml="true" value="${empty value ? 'None' : value}" />