实现接口的 Java class 可以自动继承注释吗？

Question

Suppose I had an interface with some annotation(s), for example:

@SpecialClass
public interface IFoo { /* ... */ }

And suppose I make a class that implements the interface:

public class Foo implements IFoo { /* ... */ }

Is it possible for class Foo to somehow "inherit" or automatically copy all or some of the annotations from IFoo and its members (eg automagically annotate Foo as @SpecialClass , etc.)?

This would be convenient for implementing web service classes (eg those generated by the JAX-WS "wsimport" tool) by just implementing their annotated interfaces without explicitly having to copy the interface annotations to the implementing class (eg javax.jws.WebService , javax.xml.ws.RequestWrapper , etc).

Answer 1

EDIT: I'm leaving this answer here for general information and future readers, but Andreas pointed out an important bit of the Javadoc which I'd missed:

Note that this meta-annotation type has no effect if the annotated type is used to annotate anything other than a class. Note also that this meta-annotation only causes annotations to be inherited from superclasses; annotations on implemented interfaces have no effect.

In other words, it wouldn't help in this situation. Also it's only useful if you have control over the annotation itself, of course.

I suspect the real answer is that you simply have to apply the annotation everywhere. If you're worried about forgetting one, you might want to write a unit test which finds all your classes (easier said than done, I realise) and checks that the annotation is present for all classes implementing the given interface.

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Have you tried applying the Inherited annotation to the SpecialClass annotation itself?

Indicates that an annotation type is automatically inherited. If an Inherited meta-annotation is present on an annotation type declaration, and the user queries the annotation type on a class declaration, and the class declaration has no annotation for this type, then the class's superclass will automatically be queried for the annotation type. This process will be repeated until an annotation for this type is found, or the top of the class hierarchy (Object) is reached. If no superclass has an annotation for this type, then the query will indicate that the class in question has no such annotation.

That certainly sounds like exactly what you want.