Spring 3 - Dynamic Autowiring at runtime based on another object attribute

Question

I am working on a Spring 3.1 MVC application and for one of my scenarios, I had to write two implementations of a DAO. I would like to know how to autowire this in a service

Answer 1

Since Vehicle is a @Model it is a runtime value, you won't be able to use it for autowiring values.

The vehicle has to be passed to the service methods as an argument.

public interface VehicleService { void doSomething(Vehicle vehicle); }

Assuming both CarDao and TrainDAO are implementing the same VehicleDao Service, other wise it won't make much sense.

So in your VehicleServiceImpl I would recommend you to write a method like getVehicleDao(Vehicle v){} to get the correct instance of the dao.

public class VehicleServiceImpl implements VehicleService {

    @Resource(name="carDAO")
    private VehicleDao carDAO ;


    @Resource(name="trainDAO")
    private VehicleDao trainDAO ;

    private VehicleDao getDao(Vehicle v){
        if(v instanceof Train){
            return trainDao;
        } else if(v instanceof Car) {
            return carDao;
        } else {
            throw new RuntimeException("unsupported vehicle type");
        }
    }

    void doSomething(Vehicle vehicle){
        VehicleDao dao = getDao(vehicle);
        dao.doSomethind(vehicle);
    }
}