Access Enum value using EL with JSTL

If using Spring MVC, the Spring Expression Language (SpEL) can be helpful:

<spring:eval expression="dp.status == T(com.example.Status).VALID" var="isValid" />
<c:if test="${isValid}">
   isValid
</c:if>

A simple comparison against string works:

<c:when test="${someModel.status == 'OLD'}">

You have 3 choices here, none of which is perfect:

1. You can use a scriptlet in the test attribute:

   <c:when test="<%= dp.getStatus() == Status.VALID %>">

   This uses the enum, but it also uses a scriptlet, which is not the "right way" in JSP 2.0. But most importantly, this doesn't work when you want to add another condition to the same when using ${}. And this means all the variables you want to test have to be declared in a scriptlet, or kept in request, or session (pageContext variable is not available in .tag files).

2. You can compare against string:

   <c:when test="${dp.status == 'VALID'}">

   This looks clean, but you're introducing a string that duplicates the enum value and cannot be validated by the compiler. So if you remove that value from the enum or rename it, you will not see that this part of code is not accessible anymore. You basically have to do a search/replace through the code each time.

3. You can add each of the enum values you use into the page context:

   <c:set var="VALID" value="<%=Status.VALID%>"/>

   and then you can do this:

   <c:when test="${dp.status == VALID}">

I prefer the last option (3), even though it also uses a scriptlet. This is because it only uses it when you set the value. Later on you can use it in more complex EL expressions, together with other EL conditions. While in option (1) you cannot use a scriptlet and an EL expression in the test attribute of a single when tag.