@Inject interface with two implementation

Question

I am using Microprofile and I have a question. I have an interface with a method inside:

public interface CheckData extends Serializable{
  MyObject retrieveData(String name);
}

This interface is implemented by 2 different classes( Class A and Class B).

In the service class I need to use class A or class B based on a condition.

I did the @Inject of my interface:

@ApplicationScoped
public class MyService{

@Inject
private CheckData checkData;

public Response manageData{

...

if(condition)
   checkData.retrieveData(name) // i needed Class A implementation

if(condition)
   checkData.retrieveData(name) // i needed Class B implementation

}  
}

how do you specify which implementation to use?

See this: https://stackoverflow.com/questions/55618095/how-to-inject-two-instances-of-two-different-classes-which-implement-the-same-in — Asif Bhuyan, Apr 06 '22 at 09:44
You could inject all CheckData-Beans with `@Inject Instance checkDatas;` and iterate over them to pick the right one. — Turo, Apr 06 '22 at 10:00
Instance implements Iterator, but the solution with the Classifiers might be easier, if the number of implementations is fix — Turo, Apr 06 '22 at 10:04

score 2 · Accepted Answer · answered Apr 06 '22 at 10:44

I solved it this way. I have created a class with two qualifiers:

public class MyQualifier {
  @Qualifier
  @Retention(RetentionPolicy.RUNTIME)
  @Target({ElementType.FIELD, ElementType.TYPE, ElementType.METHOD})
  public @interface ClassifierOne {
  }



  @Qualifier
  @Retention(RetentionPolicy.RUNTIME)
  @Target({ElementType.FIELD, ElementType.TYPE,ElementType. METHOD})
  public @interface ClassifierTwo {
  }
}

later I added the qualifiers to the classes that implement the interface:

@ClassifierOne
public class A implements CheckData{
...
}

@ClassifierTwo
public class B implements CheckData{
...
}

Finally I injected the interface specifying the qualifier:

@Inject
@ClassifierOne
private CheckData myClassA;

@Inject
@ClassifierTwo
private CheckData myClassB;

I hope it is correct and can help others.

Thanks to @Turo and @Asif Bhuyan for the support

@Inject interface with two implementation

1 Answers1