How to use an array constant in an annotation

Question

I would like to use constants for annotation values.

interface Client {

    @Retention(RUNTIME)
    @Target(METHOD)
    @interface SomeAnnotation { String[] values(); }

    interface Info {
     String A = "a";
     String B = "b";
     String[] AB = new String[] { A, B };
    }

    @SomeAnnotation(values = { Info.A, Info.B })
    void works();

    @SomeAnnotation(values = Info.AB)
    void doesNotWork();
}

The constants Info.A and Info.B can be used in the annotation but not the array Info.AB as it has to be an array initializer in this place. Annotation values are restricted to values that could be inlined into the byte code of a class. This is not possible for the array constant as it has to be constructed when Info is loaded. Is there a workaround for this problem?

Answer 1

Why not make the annotation values an enum, which are keys to the actual data values you want?

e.g.

enum InfoKeys
{
 A("a"),
 B("b"),
 AB(new String[] { "a", "b" }),

 InfoKeys(Object data) { this.data = data; }
 private Object data;
}

@SomeAnnotation (values = InfoKeys.AB)

This could be improved for type safety, but you get the idea.

Answer 2

No, there is no workaround.