Pass array of enums in Groovy annotation

Question

I don't know why but I can't pass array to annotation which is declared as separated variable.

@Target([ ElementType.METHOD, ElementType.TYPE ])
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
@interface SomeCustomAnnotation {

  SomeEnum[] someValue()
}

_

class SomeDataFactory {

static final SOME_ENUM_ARRAY = [SOME_ENUM_1, SOME_ENUM_2].toArray()

  enum SomeEnum {
   SOME_ENUM_1, SOME_ENUM_2
   }
}

_

class SomeClass {

   @SomeAnnotation(someValue = [SOME_ENUM_1, SOME_ENUM_2]) //fine
   def someMethod1(){}

   @SomeAnnotation(someValue = SOME_ENUM_ARRAY ) //Groovyc: Expected enum value for attribute someValue in @com.somepackage.SomeAnnotation
   def someMethod2(){}
}

Any ideas?

Answer 1

Annotations expect inline constants. So what you're trying to achieve cannot be done, even if variables are declared static and final..

Given that you're already using a separate class to provide the array, you can replace SomeAnnotation with its "provider".

There are many ways to do this, but here is an example using a different enum:

enum SomeDataProvider {

    SOME_ENUM_ARRAY_PROVIDER([SOME_ENUM_1, SOME_ENUM_2]);

    private List<SomeAnnotation> array

    SomeDataProvider(def array) {
         this.array = array
    }

    public List<SomeAnnotation> getSomeEnumArray() {
       return array;
    }
}

Then change the code declaring the annotation to:

@SomeAnnotation(someValue = SOME_ENUM_ARRAY_PROVIDER)
def someMethod2(){}

Of course, you would need to change the type expected by SomeCustomAnnotation :

@interface SomeCustomAnnotation {

  SomeDataProvider[] someValue()
}

And the processing to obtain SomeEnum[] rather by calling:

methodg.getDeclaredAnnotation(SomeAnnotation.class)
       .someValue()
       .getSomeEnumArray();

You could also replace the SomeDataProvider with an interface and make SomeAnnotation take a java.lang.Class object.