如何获取类及其超类的注释列表 [英] How to get the list of annotations of a class and its superclass

问题描述

我正在编写一个方法，用于检索声明类及其超类的特定方法的所有注释.

I'm writing a method supposed to retrieve all annotations of a specific method declaring class and its superclasses.

通过在声明类上使用方法 getAnnotations()，结果表只包含声明类注释，忽略超类注释.如果我删除声明类的注释，则存在超类注释.

By using the method getAnnotations() on the declaring class, the resulting table contains only the declaring class annotations and the superclass annotations are ignored. If I remove the annotations of the declaring class, then the superclass annotation are present.

我在这里遗漏了什么?

检索注释的简化方法:

public void check(Method invokedMethod) {
    for (Annotation annotation : invokedMethod.getDeclaringClass().getAnnotations()) {
        // Do something ...
    }
}

(我正在尝试获取的所有注释都有 @Inherited 注释)

(All annotations I'm trying the get have the @Inherited annotation)

推荐答案

如果你需要处理多个相同类型的注解，标准的做法是行不通的，因为注解存储在一个Map 以注释类型为键.(查看更多 此处).以下是我将如何解决此问题(只需手动检查所有超类):

In case you need to process several annotations of the same type, the standard approach is does not work, because annotations are stored in a Map with annotation types as the key. (See more here). Here is how I would work around this problem (just go through all super classes manually):

import java.lang.annotation.Annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Method;

public class AnnotationReflectionTest {
    public static void main(String[] args) throws Exception {
        check(Class2.class.getMethod("num", new Class[0]));
    }

    public static void check(Method invokedMethod) {
        Class<?> type = invokedMethod.getDeclaringClass();
        while (type != null) {
            for (Annotation annotation : type.getDeclaredAnnotations()) {
                System.out.println(annotation.toString());
            }
            type = type.getSuperclass();
        }
    }
}

@Inherited
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface Annot1 {
    int num();
}

@Annot1(num = 5)
class Class1 {
    public int num() {
        return 1;
    }
}

@Inherited
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface Annot2 {
    String text();
}

@Annot2(text = "ttt")
class Class2 extends Class1 {
    public int num() {
        return super.num() + 1;
    }
}

您使用什么版本的 Java 和操作系统?

What version of Java and what OS do you use?

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