java方法注释继承

Question

所以，我的问题是，我使用注释来标记类的方法

我的主要注释是@Action，我需要一个针对特定方法的更强注释，即@SpecificAction

所有用@SpecificAction注释的方法都必须注释为@Action。 我的想法是用@Action注释@SpecificAction

@Action
[other irrelevant annotations]
public @interface SpecificAction{}

与

@SpecificAction
public void specificMethod(){}

我希望specificMethod.isAnnotationPresent(Action.class)是真的，但事实并非如此

我怎样才能使@Action注释被“继承”呢

Answer 1

正如@assylias的链接所说，注释不能被继承，但您可以使用组合，递归搜索目标注释，如下所示：

public static class AnnotationUtil {

    private static <T extends Annotation> boolean containsAnnotation(Class<? extends Annotation> annotation, Class<T> annotationTypeTarget, Set<Class<? extends Annotation>> revised) {
        boolean result = !revised.contains(annotation);
        if (result && annotationTypeTarget != annotation) {
            Set<Class<? extends Annotation>> nextRevised = new HashSet<>(revised);
            nextRevised.add(annotation);
            result = Arrays.stream(annotation.getAnnotations()).anyMatch(a -> containsAnnotation(a.annotationType(), annotationTypeTarget, nextRevised));
        }
        return result;
    }

    public static <T extends Annotation> boolean containsAnnotation(Class<? extends Annotation> annotation, Class<T> annotationTypeTarget) {
        return containsAnnotation(annotation, annotationTypeTarget, Collections.emptySet());
    }

    public static <T extends Annotation> Map<Class<? extends Annotation>, ? extends Annotation> getAnnotations(Method method, Class<T> annotationTypeTarget) {
        return Arrays.stream(method.getAnnotations()).filter(a -> containsAnnotation(a.annotationType(), annotationTypeTarget)).collect(Collectors.toMap(a -> a.annotationType(), Function.identity()));
    }
}

如果你有：

@Retention(RetentionPolicy.RUNTIME)
@interface Action {
}

@Action
@Retention(RetentionPolicy.RUNTIME)
@interface SpecificAction {
}

@Action
@Retention(RetentionPolicy.RUNTIME)
@interface ParticularAction {
}

public class Foo{
    @SpecificAction
    @ParticularAction
    public void specificMethod() {
         // ...
    }
}

您可以这样使用：AnnotationUtil.getAnnotations(specificMethod, Action.class);，这将返回一个映射：{interface foo.ParticularAction=@foo.ParticularAction(), interface foo.SpecificAction=@foo.SpecificAction()}