如何Java方法的注释与方法重载一起工作？ [英] How do Java method annotations work in conjunction with method overriding?

问题描述

我有一个父类父和一个子类儿童，这样定义的：

 类父{
    @MyAnnotation（你好）
    无效美孚（）{
        //执行无关
    }
}
类儿童{
    @覆盖
    富（）{
        //执行无关
    }
}
 

如果我获得方法参照儿童:: foo的，将 childFoo。 getAnnotation（MyAnnotation.class）给我 @MyAnnotation ？还是会空？

我有兴趣更加广泛的如何或者是否标注适用于Java继承。

解决方案

我用谷歌搜索Java注释继承，我发现（从逐字复制<一个href=\"http://www.eclipse.org/aspectj/doc/released/adk15notebook/annotations.html#annotation-inheritance\">http://www.eclipse.org/aspectj/doc/released/adk15notebook/annotations.html#annotation-inheritance):

  

注释继承

  
  

明白与注释的继承规则，因为这些对基于注释的presence或无连接点匹配的轴承是非常重要的。

  
  

在默认情况下的注解是不能继承。考虑下面的程序

  @MyAnnotation
        类超级{
          @OneWay公共无效美孚（）{}
        }        子类扩展超级{
          公共无效美孚（）{}
        }
 

  

然后子不具有 MyAnnotation 注释和 Sub.foo（） 不是 @Oneway 方法，尽管它覆盖的事实 Super.foo（）是

  
  

如果注释类型有元注释 @Inherited 那么该类型的类的注释将导致标注由子类继承。因此，在上面的例子中，如果 MyAnnotation 类型有 @Inherited 属性，那么子将有 MyAnnotation 注释。

  
  用来注释不是类型以外的任何时候

@Inherited 注释不继承。从未实现一个或多个接口，A型继承它实现了接口的任何注解。

你问之前，请搜索。

I have a parent class Parent and a child class Child, defined thus:

class Parent {
    @MyAnnotation("hello")
    void foo() {
        // implementation irrelevant
    }
}
class Child {
    @Override
    foo() {
        // implementation irrelevant
    }
}

If I obtain a Method reference to Child::foo, will childFoo.getAnnotation(MyAnnotation.class) give me @MyAnnotation? Or will it be null?

I'm interested more generally in how or whether annotation works with Java inheritance.

解决方案

I Googled "Java annotation inheritance" and I found (copied verbatim from http://www.eclipse.org/aspectj/doc/released/adk15notebook/annotations.html#annotation-inheritance):

Annotation Inheritance

It is important to understand the rules relating to inheritance of annotations, as these have a bearing on join point matching based on the presence or absence of annotations.

By default annotations are not inherited. Given the following program

        @MyAnnotation
        class Super {
          @Oneway public void foo() {}
        }

        class Sub extends Super {
          public void foo() {}
        }

Then Sub does not have the MyAnnotation annotation, and Sub.foo() is not an @Oneway method, despite the fact that it overrides Super.foo() which is.

If an annotation type has the meta-annotation @Inherited then an annotation of that type on a class will cause the annotation to be inherited by sub-classes. So, in the example above, if the MyAnnotation type had the @Inherited attribute, then Sub would have the MyAnnotation annotation.

@Inherited annotations are not inherited when used to annotate anything other than a type. A type that implements one or more interfaces never inherits any annotations from the interfaces it implements.

Please search before you ask.

这篇关于如何Java方法的注释与方法重载一起工作？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！