How to declare a Spring bean autowire-candidate="false" when using annotations?

Question

I am using @ComponentScan and @Component to define my spring beans. What I would like is to declare one of these beans to be autowire-candidate=false.

This could be done with this attribute in xml. Isn't there the equivalent in annotations?

The reason I want this is because I have 2 implementations of the same interface and I don't want to use @Qualifier.

EDIT: Using @Primary is a valid work-around, but autowire-candidate seems to me like a useful feature with its own semantics.

Thanks

Answer 1

Looks like Spring refused autowire-candidate=false concept and it no longer supported. There is no analogue with annotations, so @Primary is the best work-around as you noticed.

Another way is to use custom org.springframework.beans.factory.support.AutowireCandidateResolver, which is used in DefaultListableBeanFactory, with logic that exclude undesirable beans from autowire candidates. In such case, the technology will be similar to that used for autowire-candidate=false in SimpleAutowireCandidateResolver.

Answer 2

Since Spring 5.1 , you can configure autowire-candidate in @Bean through autowireCandidate attribute:

@Bean(autowireCandidate = false)
public FooBean foo() {
      return newFooBean();
}

Answer 3

You can also use the bean accessor to tune it's visibiltiy.

see Bean visibility

@Configuration
public abstract class VisibilityConfiguration {

    @Bean
    public Bean publicBean() {
        Bean bean = new Bean();
        bean.setDependency(hiddenBean());
        return bean;
    }

    @Bean
    protected Bean hiddenBean() {
        return new Bean("protected bean");
    }
}

You can then @Autowire the Bean class and it will autowire the public bean (without complaining about multiple matching beans)

As a class' definition (unless embedded) does not allow private / protected accessor the work around would be to use an @Configuration class that would instantiate all the beans an publish the public beans while hiding the private/protected (instead of directly annotating the classes @Component \ @Service)

Also package-protected accessor may worth a try to hide @Component annotated classes. I don't know if that may work.

Answer 4

We can do this by using the @Qualifier annotations with name mentioned in the @Component annotations Bean classes -

@Component("fooFormatter")
public class FooFormatter implements Formatter {
    public String format() {
        return "foo";
    }
}
@Component("barFormatter")
public class BarFormatter implements Formatter {
    public String format() {
        return "bar";
    }
}

Injecting bean in service class -

public class FooService {
    @Autowired
    @Qualifier("fooFormatter")
    private Formatter formatter;
}

For more details please refer - https://www.baeldung.com/spring-autowire#disambiguation. Above example taken from this link.

Answer 5

Use Object type to create the Bean you want to hide

@Configuration
public class MyConfiguration {

    @Bean
    public MyInterface publicBean() {
        return new MyInterfaceImpl1();
    }

    @Bean
    protected Object hiddenBean() {
       return new MyInterfaceImpl2();
    }
}

Then you can use a simple @Autowired to inject publicBean

@Component
public class MyService {

    @Autowired
    MyInterface publicBean;

}

And even if you wanted to inject also hiddenBean in other place, then you could using @Qualifier

@Component
public class OtherComponent {

    @Autowired
    @Qualifier("hiddenBean")
    MyInterface hiddenBean;

}