java - 注解不是继承自接口(interface)方法

Question

我有一个带有注释方法的接口(interface)。注释用 @Inherited 标记，所以我希望实现者继承它。然而，事实并非如此:

代码:

import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Method;
import java.util.Arrays;

public class Example {

    public static void main(String[] args) throws SecurityException, NoSuchMethodException {
        TestInterface obj = new TestInterface() {
            @Override
            public void m() {}
        };

        printMethodAnnotations(TestInterface.class.getMethod("m"));
        printMethodAnnotations(obj.getClass().getMethod("m"));
    }

    private static void printMethodAnnotations(Method m) {
        System.out.println(m + ": " + Arrays.toString(m.getAnnotations()));
    }
}

interface TestInterface {
    @TestAnnotation
    public void m();
}

@Retention(RetentionPolicy.RUNTIME)
@Inherited
@interface TestAnnotation {}

上面的代码打印:

public abstract void annotations.TestInterface.m(): [@annotations.TestAnnotation()]

public void annotations.Example$1.m(): []

所以问题是为什么 obj.m() 没有 @TestAnnotation 尽管它实现了一个标记为 @TestAnnotation 的方法哪个是 @Inherited？

Answer 1

来自javadocs java.lang.annotation.Inherited:

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.