How to force annotations to have an "id" field?

Question

I have the following annotation:

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface IdentifiableMethod {
    String id() default "";
}

I will have to loop through a list of annotations and for each of them, perform a annotation.id().

Hence, I would have liked to use this "base" annotation to make it extended by other annotations:

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface SpecificMethod extends IdentifiableMethod{
    //invalid: annotation cannot have extends list
}

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface OtherSpecificMethod extends IdentifiableMethod{
    //invalid: annotation cannot have extends list
}

... and then generically access the .id() method in a loop by getting in parameter a List<A extends IdentifiableMethod>, so that the compiler always makes me access that method.

However, I've just found out that in the Java specification, all Java annotations extend natively the interface Annotation and they cannot have an extends list [Source: this Stack Overflow question and its answers].

Is there any way to reach something similar?

Just to clarify the need, I need to get all the methods of all the classes within my package by reflection and scan for these annotations. They may be different (they may have more or less properties, different usages etc.), but they all need to have a String id field:

List<Class<?>> classes = getClasses(packageName);
for (Class<?> clazz : classes) {
    for (Method method : clazz.getMethods()) {
        for (Class<A> annotation : annotations) { //<-- annotations is a Collection<Class<A extends Annotation>>
            if (method.isAnnotationPresent(annotation)) {
                A targetAnnotation = method.getAnnotation(annotation);
                String id = targetAnnotation.id(); //<-- this is not valid because A extends Annotation, not IdentifiableMethod
                //rest of code (not relevant)
            }
        }
    }
}

P.s. I already did this but I was looking for something cleaner:

String id = targetAnnotation.getClass().getMethod("id").invoke(targetAnnotation).toString();

How to force annotations to have an "id" field?

0 Answers0