Dyamically choose service implementation in Spring

Question

I am using spring 3.2 and would like to dynamically choose a service implementation in my controller depending on a condition. Consider I have an interface and two implementations as follows :

public interface DevService {
   public void add(Device device);
}

public class DevServiceImpl implements DevService {
    public void add(Device device) {
    }
}

public class RemoteDevServiceImpl implements DevService {
    public void add(Device device) {
    }
}

So in my controller, depending on whether the action is to be executed on the local site or remote site, I need to either execute it locally or send a command to the remote site to execute it. Essentially the site on which the user clicks determines which service impl to call. Can anybody suggest a clean way to achieve this ?

Answer 1

Assuming you need both implementations in production environment (if not - use Spring profiles to clearly split beans between environments). Simple approach would be:

interface DevService
{
   void add(Device d);
   String getName();
}

@Service("devServiceLocal")
class DevServiceLocalImpl implements DevService
{
   void add(Device d) {...}
   String getName() {return "local";}
}

class Controller
{
   @Autowired
   Collection<DevService> services;

   void doSomethingWithService()
   {
      // TODO: Check type somehow
      String servType = "local";
      for(DevService s: services)
      {
         if(servType.equals(s.getName())
         {
            // Call service methods
            break;
         }
      }
   }
}

Answer 2

Your question implies that by "dynamically" you mean that you'd like to be able to select at startup time, but that you don't need to be able to change it midrun. If that's the case, I very strongly recommend using @Profile. My usual practice, using annotation-based configuration, is to have a separate @Configuration class for each profile that defines the profile-specific @Beans that need to be available there. It's even easy to define development-only @Controllers that are completely disabled in production mode. Define a class with String constants for each profile to avoid typos.