java如何获取注释元素的默认值？

Question

假设我有一个注释

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MyAnnotation {
    int value() default 1;
}

是否有任何方法可以使用反射或其他方法获得1的值

Answer 1

是的，你可以使用^{}

Returns the default value for the annotation member represented by this Method instance.

以下面的例子为例

public class Example {
    public static void main(String[] args) throws Exception {
        Method method = Example.class.getMethod("method");
        MyAnnotation annot = method.getAnnotation(MyAnnotation.class);
        System.out.println(annot.value()); // the value of the attribute for this method annotation
        Method value = MyAnnotation.class.getMethod("value");
        System.out.println(value.getDefaultValue()); // the default value
    }

    @MyAnnotation(42)
    public static void method() {

    }
}

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@interface MyAnnotation {
    int value() default 1;
}

它会打印

42
1

Answer 2

怎么样

MyAnnotation.class.getMethod("value").getDefaultValue()