Question

I have the following scenario:

class A  with "bean-a" in wireup.xml  

class B extends A  with "bean-b" in wireup.xml  

Since B is also A, which means there are more than one instance of class A in application context.

I want to uniquely identify the singleton instance of class B, so I used

@Qualifier("unique_name") in class B 

and

<qualifier value="unique_name"/>  in "bean-b" of wireup.xml   

But the issue is still there, I get message as :

No unique bean of type [A] is defined: expected single matching bean but found 2: [A, B]  

How do I resolve this?

Thank you

Answer 1

The @Qualifier should not be put in classB. Instead it should be put along with autowired.
Your class should look like,

Class MyClass {

  @AutoWired
  @Qualifier("unique_name")
  private B b;

  //...

}

By this means you are telling autowire the b with of type B (type B or A because B is subclass of A) but with a bean definition which has the qualifier “unique_name”. The wireup.xml has the qualifier tag assigned to bean-b. Your wireup.xml might look like this

<bean id="bean-A" class="com.domain.A" />
<bean id="bean-B" class="com.domain.B"
  <qualifier="unique_name" />
</bean>