spring-question-multiple-beans-same-type.md

Multiple Beans with the Same Type

The Spring application has an interface

public interface UserService {
  // ...
}

with the only implementation

@Service
public class RegularUserService implements UserService {
  // ...
}

The application also contains one hundred services using UserService exactly the same way as it's shown below:

@Service
public class Service1 {
  @Autowired
  private UserService userService;

  // ...
}

@Service
public class Service2 {
  @Autowired
  private UserService userService;

  // ...
}

// ...

@Service
public class Service100 {
  @Autowired
  private UserService userService;

  // ...
}

You got an assignment to

• implement one more UserService bean working with privileged users, let's call it PrivilegedUserService.
• use PrivilegedUserService in only one service, let's say, Service100. All other services should continue to use good old RegularUserService.

You've done with the first part:

@Service
public class PrivilegedUserService implements UserService {
  // ...
}

How would you complete the second one?

Follow-up:

Can you do it with no touching the rest 99 services?