Question

我不确定如何在Spring中使用自定义限定符界面进行组件扫描和自动装配。我有一个界面：

@Target({ElementType.FIELD,ElementType.PARAMETER,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Qualifier
public @interface BigBean {
}

我要注入的bean：

@Component
public class Bean {

   @Autowired
   @BigBean("A")
   private SomeBean sb;

   public SomeBean getSb() {
       return sb;
   }
   public void setSb(SomeBean sb) {
       this.sb = sb;
   }
}

和要通过自定义限定符区分的相同类型的bean：

@Component
@BigBean("A") //<-????
public class SmallBeanA implements SomeBean{
}

@Component
public class SmallBeanB implements SomeBean{
}

我在spring documentation中找到的内容并没有在我的案例中编译。如何使用我的自定义限定符？

Answer 1

您需要将属性值添加到BigBean注释中

@Target({ElementType.FIELD,ElementType.PARAMETER,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Qualifier
public @interface BigBean {

    String value() default "";
}

Answer 2

这现在有点旧了，不确定我的答案是否有帮助，但让我尝试。下面是注入SomeBean选定实例的代码。

@Qualifier
@Target({ ElementType.FIELD, ElementType.PARAMETER, ElementType.METHOD, ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
public @interface BigBean {
    String value() default "";
}


public interface SomeBean { 
}


@Component
@BigBean("A")
public class SmallBeanA implements SomeBean {
    private SmallBeanA() {
        System.out.println("SmallBeanA constructed");
    }
    @Override
    public String toString() {
        return "SmallBeanA";
    }
}


@Component
@BigBean("B")
public class SmallBeanB implements SomeBean{
    private SmallBeanB() {
        System.out.println("SmallBeanB constructed");
    }
    @Override
    public String toString() {
        return "SmallBeanB";
    }
}


@Component
public class Bean {
    @Autowired
    @BigBean("A")
    private SomeBean sb;
    public SomeBean getSb() {
        return sb;
    }
    @Override
    public String toString() {
        return "Bean [sb=" + sb + "]";
    }
}



public class QualifierTest {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("Spring-Module.xml");
        Bean myBean = context.getBean(Bean.class);
        System.out.println(myBean.getSb().toString());
        //OR
        System.out.println(myBean.toString());
    }
}

定制@Qualifier与Spring autoconfig

2 个答案: