Freemarker: an enum in an if statement

Question

In my if statement, I want to compare a variable, which is a JDK 1.5 enum, to an enum literal. For example:

<#if type == ProblemStatisticType.BEST_SOLUTION_CHANGED>
  ...
</#if>

But I get this exception:

freemarker.core.InvalidReferenceException: Expression ProblemStatisticType is undefined on line 430, column 87 in index.html.ftl.
at freemarker.core.TemplateObject.assertNonNull(TemplateObject.java:125)
at freemarker.core.TemplateObject.invalidTypeException(TemplateObject.java:135)

How can I do that?

Solution 1

Unfortunately, the FreeMarker language doesn't have the concept of classes... but you can do this:

<#if type.name() == "BEST_SOLUTION_CHANGED">
  ...
</#if>

Or if you trust the toString() for the enum type, the .name() part can be omitted.

Solution 2

If you want to compare enums you should specify a constant enum value in double quotes like:

<#if type == "BEST_SOLUTION_CHANGED">
  ...
</#if>

Solution 3

I have used something like this successfully (in java 1.6 and 1.7, have not tried 1.5):

<#if type?? && statics["com.your.package.ContainingClass$TypeEnum"].BEST_SOLUTION_CHANGED.equals(type)>
  Do some freemarker or HTML here
</#if>

This is with enum inside another class like:

class ContainingClass {
   public enum TypeEnum {
    WORST(0),
    BEST_SOLUTION_CHANGED(1);

    private int value;

    private TypeEnum(int value) {
      this.value = value;
    }

    public int value() {
      return this.value;
    }
  };  
}

And type variable is defined in java something like:

TypeEnum type = TypeEnum.BEST_SOLUTION_CHANGED;