Java 从抽象类继承注解？
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Inherit annotations from abstract class?
提问by membersound
Can I somehow group a set of annotations on an abstract class, and every class that extends this class has automatically assigned these annotations?
我能否以某种方式对抽象类上的一组注释进行分组，并且每个扩展该类的类都自动分配了这些注释？
At least the following does not work:
至少以下不起作用：
@Service
@Scope(value = BeanDefinition.SCOPE_PROTOTYPE)
class AbstractService
class PersonService extends AbstractService {
@Autowired //will not work due to missing qualifier annotation
private PersonDao dao;
}
采纳答案by Philipp Sander
The answer is: no
答案是不
Java annotations are not inherited unless the annotation type has the @Inherited meta-annotation on it: https://docs.oracle.com/javase/7/docs/api/java/lang/annotation/Inherited.html.
除非注释类型具有 @Inherited 元注释，否则不会继承 Java 注释：https: //docs.oracle.com/javase/7/docs/api/java/lang/annotation/Inherited.html。
Spring's @Componentannotation does not have @Inherited on it, so you will need to put the annotation on each component class. @Service, @Controller and @Repository neither.
Spring 的@Component注解上没有 @Inherited，因此您需要将注解放在每个组件类上。@Service、@Controller 和 @Repository 都不是。
回答by Kuba Spatny
I have this piece of code in my project and it works just fine, although it's not annotated as Service:
我的项目中有这段代码，它工作得很好，虽然它没有被注释为服务：
public abstract class AbstractDataAccessService {
@Autowired
protected GenericDao genericDao;
}
and
和
@Component
public class ActorService extends AbstractDataAccessService {
// you can use genericDao here
}
So you don't need to put annotation on your abstract class but even if you do you will still have to put annotation on all subclass as @Componentor @Serviceannotations are not inherited.
因此，您不需要在抽象类上添加注释，但即使这样做，您仍然必须在所有子类上添加注释，@Component否则@Service注释不会被继承。
回答by Erwin Bolwidt
The short answer is: with the annotations that you mentioned in your example, no.
简短的回答是：使用您在示例中提到的注释，没有.
The long answer: there is a meta-annotation called java.lang.annotation.Inherited. If an annotation itself is annotated with this annotation, then when a class is annotated with it, its subclasses are also automatically annotated with it by implication.
答案很长：有一个名为java.lang.annotation.Inherited. 如果一个注解本身用这个注解进行注解，那么当一个类用它注解时，它的子类也自动用它进行注解。
However, as you can see in the spring source code, the @Serviceand @Scopeannotation are not themselves annotated with @Inherited, so the presence of @Serviceand @Scopeon a class is not inherited by its subclasses.
但是，正如您在 spring 源代码中看到的那样，@Service和@Scope注释本身没有用 进行注释@Inherited，因此类上的@Service和的存在@Scope不会被其子类继承。
Maybe this is something that can be fixed in Spring.
也许这是可以在 Spring 中解决的问题。
