NoUniqueBeanDefinitionException: Don't Control Bean Creation Class

Question

In Spring, is it possible to avoid a NoUniqueBeanDefinitionException in the following scenario:

• My application references beans in a 3rd party library

   appBean="thirdPartyClass"
  

• The bean code is in a 3rd party library I can't edit

   @Component
   public class ThirdPartyClass {
  
       @Autowired
       private ThirdPartyInterface thirdPartyInterface;
  

• The third party interface is used by two classes I do control

This class:

  public class MyClass1 implements ThirdPartyInterface {

and this class:

   public class MyClass2 implements ThirdPartyInterface {

Currently, NoUniqueBeanDefinitionException is occurring when I try to start my application saying the following:

org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'thirdPartyClass': Unsatisfied dependency expressed through field 'thirdPartyIntereface'; nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type 'ThirdPartyInterface' available: expected single matching bean but found 2: MyClass1,MyClass2

Answer 1

Considering you cannot change the ThirdPartyClass class.

Make one of the implemented classes as @Primary to be considered as the primary bean to be Autowired in the ThirdPartyClass class.

@Primary
@Component
public class MyClass1 implements ThirdPartyInterface {
}

And add @Qualifier to the other implemented class. And use that same qualifier in your other classes to Autowire and use it seamlessly.

@Component
@Qualifier("queue2")
public class MyClass2 implements ThirdPartyInterface {
}

@Component
public class MyOtherClass {
     @Autowired
     @Qualifier("queue2")
     private ThirdPartyInterface thirdPartyInterface;
}

Answer 2

The error clearly says what the problem is -

When you have 2 class implementing same interface and you are trying to use @Autowired via the interface, Spring does not know which implementation to pick (MyClass1 or MyClass2).

You need to be specific. Use @Qualifier to specify which implementation to pick.

I quickly found one example here - Spring @Autowired and @Qualifier