Qualifying By Name

To qualify by name, use the Named annotation. For example, consider the following classes:

public interface Engine { (1)
    int getCylinders();
    String start();
}
@Singleton
public class V6Engine implements Engine {  (2)
    @Override
    public String start() {
        return "Starting V6";
    }
    @Override
    public int getCylinders() {
        return 6;
    }
}
@Singleton
public class V8Engine implements Engine {  (3)
    @Override
    public String start() {
        return "Starting V8";
    }
    @Override
    public int getCylinders() {
        return 8;
    }
}
@Singleton
public class Vehicle {
    private final Engine engine;
    @Inject
    public Vehicle(@Named("v8") Engine engine) {(4)
        this.engine = engine;
    }
    public String start() {
        return engine.start();(5)
    }
}

interface Engine { (1)
    int getCylinders()
    String start()
}
@Singleton
class V6Engine implements Engine { (2)
    int cylinders = 6
    @Override
    String start() {
        "Starting V6"
    }
}
@Singleton
class V8Engine implements Engine { (3)
    int cylinders = 8
    @Override
    String start() {
        "Starting V8"
    }
}
@Singleton
class Vehicle {
    final Engine engine
    @Inject Vehicle(@Named('v8') Engine engine) { (4)
        this.engine = engine
    }
    String start() {
        engine.start() (5)
    }
}

interface Engine { (1)
    val cylinders: Int
    fun start(): String
}
@Singleton
class V6Engine : Engine {  (2)
    override var cylinders: Int = 6
    override fun start(): String {
        return "Starting V6"
    }
}
@Singleton
class V8Engine : Engine {
    override var cylinders: Int = 8
    override fun start(): String {
        return "Starting V8"
    }
}
@Singleton
class Vehicle @Inject
constructor(@param:Named("v8") private val engine: Engine) { (4)
    fun start(): String {
        return engine.start() (5)
    }
}

Micronaut is capable of injecting V8Engine in the previous example, because:

@Named qualifier value (v8) + type being injected simple name (Engine) == (case-insensitive) == The simple name of a bean of type Engine (V8Engine)

You can also declare @Named at the class level of a bean to explicitly define the name of the bean.