JAVA-如何从注释中获取注释? [英] JAVA - How to get annotations from Annotation?

问题描述

我想从注释中获取注释，但是奇怪的是我无法从注释实例中获取单个注释.我该如何解决?我想从此注释实例中获取注释.

I want to get annotations from annotation, but the weird thing is I can't get single annotation from annotation instance. How do I solve this? I want to get annotations from this annotation instance.

public static void test(Annotation annotation) {
    System.out.println("ValidBoolean annotation len:" + ValidBoolean.class.getAnnotations().length);
    System.out.println(annotation.getClass().getName() + ":" + annotation.getClass().getAnnotations().length);
    if (annotation instanceof ValidBoolean) {
        ValidBoolean validBoolean = (ValidBoolean) annotation;
        System.out.println("[BOOLEAN]" + validBoolean.getClass().getName() + ":" + validBoolean.getClass().getAnnotations().length);
    }
}

打印结果是:

ValidBoolean annotation len:3
com.sun.proxy.$Proxy28:0
[BOOLEAN]com.sun.proxy.$Proxy28:0

推荐答案

如果我对您的理解正确，那么您想这样做:

If I understand you correctly, you want to do:

Annotation[] annotationAnnotations = annotation.annotationType().getAnnotations();

通常， annotationType() 如此工作

Generally, annotationType() works such that

someClass.getAnnotation(someAnnotationClass).annotationType() == someAnnotationClass

所以annotation instanceof ValidBoolean也暗示annotation.annotationType() == ValidBoolean.class，因此在它们上调用.getAnnotations()将导致相同的注释.

So annotation instanceof ValidBoolean also implies annotation.annotationType() == ValidBoolean.class, thus invoking .getAnnotations() on them will lead to the same annotations.

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