Autowiring by name (interface vs class) [SPR-16174]

[spring-projects-issues]

Max Samsonov opened SPR-16174 and commented

Lets say we have 2 beans that implement interface A:

interface A {}
class B implements A {}

@Configuration
public class C {
  @Bean public A red() { return new B(); }
  @Bean public A black() { return new B(); }
}

If we autowire them later, in 2 fields, we won't get an exception.
But, we will randomly get same bean injected in both fields.

@Service
public class ServiceImpl {
  private final A red;
  private final A black;
  public ServiceImpl(A red, A black) {
    this.red = red;
    this.black = black;
  }
}

Otherwise, if we change type of fields (from interface to class), it will work as expected.

@Service
public class ServiceImpl {
  private final B red;
  private final B black;
  public ServiceImpl(B red, B black) {
    this.red = red;
    this.black = black;
  }
}

---

Affects: 4.3.12

Issue Links:

• Field name is used to match on bean name when @Autowired matches several beans by type [SPR-16142] #20690 Field name is used to match on bean name when @Autowired matches several beans by type

[spring-projects-issues]

Juergen Hoeller commented

I can't reproduce this: Such an arrangement injects fine for me, selecting the target beans by type first and then matching each bean by name against the parameter name in a second pass. Could you please double-check your effect and provide a corresponding unit test that reliably fails for you in the interface case but works in the target class case?

FWIW, we generally recommend to be as specific as possible in your @Bean return type signature, i.e. declaring B as a return type in your scenario. This allows the container to introspect the implementation type early, not just learning about it once the bean is actually created.