How to get the list of annotations of a class and its superclass

问题

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

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.

What am I missing here?

The simplified method retrieving the annotations :

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

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

回答1:

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;
    }
}

What version of Java and what OS do you use?

来源：https://stackoverflow.com/questions/32467494/how-to-get-the-list-of-annotations-of-a-class-and-its-superclass

标签

java

inheritance

reflection

annotations