Question

Consider the following code:

@Service
class UserSpecificService {
    @Autowired ServiceA serviceA;
    @Autowired ServiceB serviceB;
    @Autowired User user;

    public void doUserSpecificThings() {
        // consume serviceA, serviceB and user here
    }
}

@Service class ServiceA {}
@Service class ServiceB {}

@Service
class Facade {
    public void doThingsForUser(Long userId) {
        User user = userService.getById(userId);
        UserSpecificService userSpecificService = ...; // !!!
        userSpecificService.doUserSpecificThings();
    } 
}

The question is about line marked with // !!!. Is there any way I can construct UserSpecificService without implementing my own factory which is aware of ServiceA and ServiceB, and only requires an instance of User to instantiate a UserSpecificService?

If it matters – I’m going to use the Facade with Spring MVC, though I’d like it not to rely on this.

Thanks!

Answer 1

Here’s a suggestion:

• make all services that are eligible to be userSpecificService (I guess these are ServiceA and serviceB) have a common interface
• let that interface have two methods – doUserSpecificThing() and isEligibleFor(user)
• use @Autowired List<YourInterface> list
• in your doThingsForUser() method iterate the list of all instances of the given interface, and for each of them check if it is eligible for the given user. If it is – invoke the method.