Get a in a interface annotated method from class

I want to access Method via reflection. The Problem is that the Method is annotated in an Interface:

public interface MyRepository extends CrudRepository<MyClass, Long> {

    @CustomAnnotation
    MyClass findByName(String name);
}

As you see I use spring which provide a class that will implement this Repository. I want to create a Method, that will get a Repository and invoke all methods that are annotated with @CustomAnnotation.

public void do(Repository<?, ?> repository){
   Method[] methods=repository.getClass().getMethodThatAreAnnotatedInInterfaceWith(CustomAnnotation.class);
   ....
}

Because the implementation of an interface won’t have the annotations of the interface present, I do not know how to query these methods.