Annotation processor: get all enum values from a TypeMirror or TypeElement

Question

I don't understand how I can retrieve the Enum values in an annotation processor.

My annotation is a custom Java Bean Validation annotation:

  @StringEnumeration(enumClass = UserCivility.class)
  private String civility;

On my annotation processor, I can access to instances of these:

javax.lang.model.element.AnnotationValue
javax.lang.model.type.TypeMirror
javax.lang.model.element.TypeElement

I know it contains the data about my enum since I can see that in debug mode. I also see ElementKind == Enum

But I want to get all the names for that Enum, can someone help me please.

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Edit: I don't have access to the Class object of this Enum, because we are in an annotation processor, and not in standart Java reflection code. So I can't call Class#getEnumConstants() or EnumSet.allOf(MyEnum.class) unless you tell me how I can get the Class object from the types mentioned above.

Answer 1

I found a solution (this uses Guava):

class ElementKindPredicate<T extends Element> implements Predicate<T> {
    private final ElementKind kind;
    public ElementKindPredicate(ElementKind kind) {
      Preconditions.checkArgument(kind != null);
      this.kind = kind;
    }
    @Override
    public boolean apply(T input) {
      return input.getKind().equals(kind);
    }
}

private static final ElementKindPredicate ENUM_VALUE_PREDICATE = new ElementKindPredicate(ElementKind.ENUM_CONSTANT);

public static List<String> getEnumValues(TypeElement enumTypeElement) {
    Preconditions.checkArgument(enumTypeElement.getKind() == ElementKind.ENUM);
    return FluentIterable.from(enumTypeElement.getEnclosedElements())
        .filter(ENUM_VALUE_PREDICATE)
        .transform(Functions.toStringFunction())
        .toList();
}