Spring：没有限定符的 Autowire bean

Question

Is it possible to autowire a bean that does NOT have the given qualifier in spring? The use case would be to have a list of all beans, but exclude one:

@Autowired
@NotQualifier("excludedBean")    // <-- can we do something like this?
List<SomeBean> someBeanList;


public class Bean1 implements SomeBean {}

public class Bean2 implements SomeBean {}

@Qualifier("excludedBean")
public class Bean3 implements SomeBean {}

In the example above someList should contain an instance of Bean1 and Bean2 but not Bean3 .

(Remark: I'm aware that the opposite would work, ie add some qualifier to Bean1 and Bean2 and then autowire with that qualifier.)

EDIT : Some further clarifications:

• All beans are in the spring context (also the one being excluded).
• Configuration needs to be annotation-based, not xml-based. Therefore, eg turning off autowired-candidate does not work .
• Autowire capability of the bean must remain in general. In other words, I want to exclude the bean from the injection point List<SomeBean> someBeanList; , but I want to autowire it somewhere else.

Answer 1

You can introduce you own annotation with meta annotations @Conditional and @Qualifier

@Target({ElementType.FIELD, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Qualifier
@Conditional(MyCondition.class)
public @interface ExcludeBean {

and then introduce class where you can do your conditional logic

public class MyCondition implements Condition {

    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        return !metadata.equals(ExcludeBean.class);
    }

}

In your Configuration class

  @Bean
  @ExcludeBean
  public BeanA beanA() {
      return new BeanA();
  }

You can also exclude bean from being candidate for autowiring by setting autowire-candidate on particular bean or by specifying default-autowire-candidates="list of candidates here"

Answer 2

main point it's bean for exclude is in context but not injected into some cases with exclude condition .

you can do exclude bean with qualifier with custom annotaion and BeanPostProcessor. (I did as example for simple case , for collection of bean type , but you can extend it)

annotaion for exclude :

@Component
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface ExcludeBeanByQualifierForCollectionAutowired {

    String qualifierToExcludeValue();

    Class<?> aClass();
}

bean post processor with injection

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.stereotype.Component;

import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.Collection;

@Component
public class ExcludeAutowiredBeanPostProcessor implements BeanPostProcessor {

    @Autowired
    private ConfigurableListableBeanFactory configurableBeanFactory;

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) {
        Field[] fields = bean.getClass().getDeclaredFields();
        for (Field field : fields) {
            field.setAccessible(true);
            ExcludeBeanByQualifierForCollectionAutowired myAutowiredExcludeAnnotation = field.getAnnotation(ExcludeBeanByQualifierForCollectionAutowired.class);
            if (myAutowiredExcludeAnnotation != null) {

                Collection<Object> beanForInjection = new ArrayList<>();

                String[] beanNamesOfType = configurableBeanFactory.getBeanNamesForType(myAutowiredExcludeAnnotation.aClass());
                for (String injectedCandidateBeanName : beanNamesOfType) {

                    Object beanCandidate = configurableBeanFactory.getBean(injectedCandidateBeanName);

                    Qualifier qualifierForBeanCandidate = beanCandidate.getClass().getDeclaredAnnotation(Qualifier.class);

                    if (qualifierForBeanCandidate == null || !qualifierForBeanCandidate.value().equals(myAutowiredExcludeAnnotation.qualifierToExcludeValue())) {
                        beanForInjection.add(beanCandidate);
                    }
                }
                try {
                    field.set(bean, beanForInjection);
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                }
            }
        }

        return bean;
    }


    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) {
        return bean;
    }
}

and example:

public class ParentBean {}

public class Bean1Included extends ParentBean {}

public class Bean2Included extends ParentBean {}

public class Bean3Included extends ParentBean {}

@Qualifier("excludedBean")
public class BeanExcluded extends ParentBean {}

configuration

@Configuration
public class BeanConfiguration {

    @Bean
    public Bean1Included getBean1(){
        return new Bean1Included();
    }

    @Bean
    public Bean2Included getBean2(){
        return new Bean2Included();
    }

    @Bean
    public Bean3Included getBean3(){
        return new Bean3Included();
    }

    @Bean
    public BeanExcluded getExcludedBean(){
        return new BeanExcluded();
    }

    @Bean
    public ExcludeAutowiredBeanPostProcessor excludeAutowiredBeanPostProcessor(){
        return new ExcludeAutowiredBeanPostProcessor();
    }
}

and result:

@ExtendWith(SpringExtension.class) // assumes Junit 5
@ContextConfiguration(classes = BeanConfiguration.class)
public class ExcludeConditionTest {

    @Autowired
    private ApplicationContext context;
    @Autowired
    private BeanExcluded beanExcluded;
    @ExcludeBeanByQualifierForCollectionAutowired(qualifierToExcludeValue = "excludedBean" , aClass = ParentBean.class)
    private List<ParentBean> beensWithoutExclude;

    @Test
    void should_not_inject_excluded_bean() {
        assertThat(context.getBeansOfType(ParentBean.class).values())
                .hasOnlyElementsOfTypes(Bean1Included.class,
                                        Bean2Included.class,
                                        Bean3Included.class,
                                        BeanExcluded.class);

        assertThat(beansWithoutExclude)
                .hasOnlyElementsOfTypes(Bean1Included.class,
                                        Bean2Included.class,
                                        Bean3Included.class)
                .doesNotHaveAnyElementsOfTypes(BeanExcluded.class);

        assertThat(beanExcluded).isNotNull();
    }
}

Answer 3

There might be two cases :

case 1 : Bean3 in not in spring context;

case 2 : Bean3 is in spring context but not injected in some cases with @Autowired ,

1. if you need to exclude bean with Qualifier from context at all ,use

   • Condition. This bean is not registered in application conxtet if matches returns false. as result :

   @Autowired List someBeanList; -- here injected all beans instanceof SomeBean and registered in application context.

   from spring api

   Condition A single condition that must be matched in order for a component to be registered. Conditions are checked immediately before the bean-definition is due to be registered and are free to veto registration based on any criteria that can be determined at that point.

2. autowired with qualifier :

   2.1 if you want to exclude bean with the some qualifier from autowired value in some bean/beans and in xml configuration you can use autowire-candidate

   2.2 also you can get all autowired values by Setter Injection and filter only beans that you need.

    //no Autowired. Autowired in method private List<ParentBean> someBeen = new ArrayList<>(); @Autowired public void setSomeBeen(List<ParentBean> beens){ // if you use java 8 use stream api for (ParentBean bean:beens) { Qualifier qualifier = bean.getClass().getAnnotation(Qualifier.class); if(qualifier == null ||!qualifier.value().equals("excludedBean")){ someBeen.add(bean); } } }

   2.3 you can use custome AutowiredAnnotationBeanPostProcessor :) and customise @Autowired for you requirements if you need something realy custom.

from spring api AutowiredAnnotationBeanPostProcessor :

Note: A default AutowiredAnnotationBeanPostProcessor will be registered by the "context:annotation-config" and "context:component-scan" XML tags. Remove or turn off the default annotation configuration there if you intend to specify a custom AutowiredAnnotationBeanPostProcessor bean definition.

Answer 4

Another way to do this, is creating a custom component with @Qualifier

@Component
@Qualifier
public @interface MyComponent {
    public boolean isMock() default false;
}

@Autowired
@MyComponent(true)
List<SomeBean> mockList; // will inject just component with "isMock = true"

@Autowired
@MyComponent(false)
List<SomeBean> notMockList; // will inject just component with "isMock = false"


@MyComponent
public class Bean1 implements SomeBean {}

@MyComponent
public class Bean2 implements SomeBean {}

@MyComponent(isMock = true)
public class Bean3 implements SomeBean {}

Obs: this code is not tested, just giving an idea