Spring @Qualifier 分组依赖注入集合

使用 Spring 的集合类依赖注入时，有时需要对多个相同类型的 Bean 进行分组。 可以使用 @Qualifier 或者自定义 Qualifier Annotation 来实现。

@Qualifier

@Configuration
public class QualifiedBeansConfig {
    private static final Logger log = LoggerFactory.getLogger(QualifiedBeansConfig.class);

    public static final String MY_QUALIFIER_A = "MY_QUALIFIER_A";
    public static final String MY_QUALIFIER_B = "MY_QUALIFIER_B";

    @Bean
    @Qualifier(MY_QUALIFIER_A)
    public MyBean myBean1() {
        return new MyBean("1");
    }

    @Bean
    @Qualifier(MY_QUALIFIER_A)
    public MyBean myBean2() {
        return new MyBean("2");
    }

    @Bean
    @Qualifier(MY_QUALIFIER_B)
    public MyBean myBean3() {
        return new MyBean("3");
    }

    @Component
    public static class BeanCollections {
        public BeanCollections(final List<MyBean> myBeansList,
                        @Qualifier(MY_QUALIFIER_A) final Set<MyBean> myBeansSet,
                        @Qualifier(MY_QUALIFIER_B) final Map<String, MyBean> myBeansMap
        ) {
            log.info("myBeansList: {}", myBeansList);
            log.info("myBeansSet: {}", myBeansSet);
            log.info("myBeansMap: {}", myBeansMap);
        }
    }
}

输出：

...   : myBeansList: [MyBean[key=1], MyBean[key=2], MyBean[key=3]]
...   : myBeansSet: [MyBean[key=1], MyBean[key=2]]
...   : myBeansMap: {myBean3=MyBean[key=3]}

自定义 Qualifier Annotation

另一种写法是使用自定义 Qualifier Annotation：

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

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

将

• @Qualifier(MY_QUALIFIER_A) 替换成 @QualifierA
• @Qualifier(MY_QUALIFIER_B) 替换成 @QualifierB

即可达到同样的效果。