NoUniqueBeanDefinitionException：没有类型的限定bean：不返回

Question

I have the below bean defined as part a A.jar

package abc;

@Component
public class ParentInterceptor implements ClientInterceptor {

}

I have created another bean in a different project under a different package by extending ParentInerceptor

package xyz;

@Component
public class ChildInterceptor extends ParentInterceptor {

}

In my SpringBoot app , I have a bean defined similar to below

@ComponentScan({"abc","xyz"})
public class Application {

    public static void main(String[] args) {
        ApplicationContext ctx =  SpringApplication.run(Application.class, args);
}

@Bean
public Data dataRepo(ParentInterceptor p){

}


}

When I run the main method , I am expecting to see NoUniqueBeanDefinitionException as 2 beans are of same type. However I see both the beans are loaded and ParentInterceptor is being used. Is there a reason why the error is not being thrown?

EDIT

However when i did the below , I was able to see the error being thrown. However I am still unable to understand why an error wasn't thrown in the case listed above.

package xyz;

@Component
public class ChildInterceptor1 extends ChildInterceptor {

}

Application Class:

 @ComponentScan({"abc","xyz"})
    public class Application {

        public static void main(String[] args) {
            ApplicationContext ctx =  SpringApplication.run(Application.class, args);
    }

    @Bean
    public Data dataRepo(ChildInterceptor p){

    }


    }

EDIT 2

I also tried to check if the child bean indeed extending the parent using the code below -

ctx.getBeansOfType(ParentInterceptor.class)

This returns ParentInterceptor & ChildInterceptor. So I am not really sure why Spring is not returning the error!

Answer 1

In your first example (Parent and Child), i have the correct behaviour, which is the NoUniqueBeanDefinitionException thrown.

If you want to specify which bean to be injected, you can use the @Qualifier annotation:

@Bean
public Data dataRepo(@Qualifier("parentInterceptor") ParentInterceptor p) {

}

Optionally, you can give a name to a component:

@Component("foo") 

and change the @Qualifier accordingly.