Not possible to transform String to enumeration value in special case

[josemgimenez]

This small class reproduces an issue we had with JUEL and OpenJDK 1.7. The interesting thing of this case is that RALPH is internally a subclass of Actor, so it is not an enum and it is not possible to transform into a member of the enumeration and according to the EL specification it should work.

package com.juel;

import de.odysseus.el.ExpressionFactoryImpl;
import de.odysseus.el.TreeValueExpression;
import de.odysseus.el.util.SimpleContext;

public class App
{
    public static enum Actor
    {
        HOMER, BART, RALPH
        {
            @Override
            public String greeting()
            {
                return "I'm special";
            }
        };

        public String greeting()
        {
            return "Hi, I'm " + name();
        }
    }

    public static void main(String[] args) throws Exception
    {
        ExpressionFactoryImpl expressionFactory = new ExpressionFactoryImpl();
        SimpleContext context = new SimpleContext();
        context.setVariable("actor", expressionFactory.createValueExpression(Actor.HOMER, Actor.class));
        context.setVariable("actor2", expressionFactory.createValueExpression(Actor.RALPH, Actor.class));

        TreeValueExpression e = expressionFactory.createValueExpression(context, "${actor == 'HOMER'}", boolean.class);
        System.out.println(e.getValue(context));

        TreeValueExpression e2 = expressionFactory.createValueExpression(context, "${actor2 == 'HOMER'}", boolean.class);
        System.out.println(e2.getValue(context)); // kaboom!
    }
}

Output:

true
Exception in thread "main" javax.el.ELException: Cannot coerce 'HOMER' of class java.lang.String to class com.juel.App$Actor$1 (incompatible type)
    at de.odysseus.el.misc.TypeConverterImpl.coerceStringToType(TypeConverterImpl.java:287)
    at de.odysseus.el.misc.TypeConverterImpl.coerceToType(TypeConverterImpl.java:348)
    at de.odysseus.el.misc.TypeConverterImpl.convert(TypeConverterImpl.java:365)
    at de.odysseus.el.tree.Bindings.convert(Bindings.java:138)
    at de.odysseus.el.misc.BooleanOperations.eq(BooleanOperations.java:161)
    at de.odysseus.el.tree.impl.ast.AstBinary$4.apply(AstBinary.java:52)
    at de.odysseus.el.tree.impl.ast.AstBinary$SimpleOperator.eval(AstBinary.java:31)
    at de.odysseus.el.tree.impl.ast.AstBinary.eval(AstBinary.java:110)
    at de.odysseus.el.tree.impl.ast.AstEval.eval(AstEval.java:51)
    at de.odysseus.el.tree.impl.ast.AstNode.getValue(AstNode.java:31)
    at de.odysseus.el.TreeValueExpression.getValue(TreeValueExpression.java:122)
    at com.juel.App.main(App.java:37)

[beckchr]

Hi!

RALPH is an enum. Please use something like ${actor2.toString() == 'HOMER'}.

[josemgimenez]

Hi,
Thanks for the response. Our current workaround is using the enum's method ".name()" to get its name.

The question is whether it should work correctly or not, as it's quite a big corner case and I couldn't find anybody with the same issue.

Also, when I mean that it is not an enum I mean that if you run System.out.println(Actor.RALPH.getClass().isEnum());
you get false on OpenJDK 1.7

[beckchr]

Using name() is better than toString() of course. Whether it should work is a good question. And to be honest, it probably should...

[lzg14]

In the "context", we know the "actor2" is a "com.juel.App$Actor", but when evaluate "${actor2 == 'HOMER'}", the eq function treat "actor2" as a Object, o1.getClass will get "com.juel.App$Actor$1". There is no way JUEL know how to convert 'HOMER' to a "com.juel.App$Actor$1". So special RALPH is indeed different from HOMER and BART. And I don't think this is a bug.
see BooleanOperations.java 136~170

[sfuhrm]

Implemented spec of JUEL is JSP 2.2 == EL 2.1:

Chapter 1.8.2 2 says:

1.8.2 A {==,!=,eq,ne} B
...
■ If A or B is an enum, coerce both A and B to enum, apply operatorr
...

Next spec EL 3.0:

The JSR-000341 Expression Language 3.0 Final Release specification from 2013 1 states in chapter 1.9.2:

1.9.2 A {==,!=,eq,ne} B
...

• If A or B is an enum, coerce both A and B to enum, apply operator
  ....

From my understanding this officially means since JUEL wants to implement EL2.1, it is a bug.