Java继承的注释
示例
默认情况下,类注释不适用于扩展它们的类型。可以通过将@Inherited注释添加到注释定义中来更改
示例
请考虑以下2个注释:
@Inherited
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface InheritedAnnotationType {
}和
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface UninheritedAnnotationType {
}如果这样注释了三个类:
@UninheritedAnnotationType
class A {
}
@InheritedAnnotationType
class B extends A {
}
class C extends B {
}运行此代码
System.out.println(new A().getClass().getAnnotation(InheritedAnnotationType.class));
System.out.println(new B().getClass().getAnnotation(InheritedAnnotationType.class));
System.out.println(new C().getClass().getAnnotation(InheritedAnnotationType.class));
System.out.println("_________________________________");
System.out.println(new A().getClass().getAnnotation(UninheritedAnnotationType.class));
System.out.println(new B().getClass().getAnnotation(UninheritedAnnotationType.class));
System.out.println(new C().getClass().getAnnotation(UninheritedAnnotationType.class));将打印与此类似的结果(取决于注释的包):
null @InheritedAnnotationType() @InheritedAnnotationType() _________________________________ @UninheritedAnnotationType() null null
请注意,注释只能从类继承,而不能从接口继承。