How to dynamically inject a service using a runtime “qualifier” variable?

You can obtain your bean from the context by name dynamically using a BeanFactory:

@Service
public class Doer {

  @Autowired BeanFactory beans;

  public void doSomething(Case case){
    CaseService service = beans.getBean(case.getCountryCode(), CaseService.class)
    service.doSomething(case);
  }
}

A side note. Using something like country code as bean name looks a bit odd. Add at least some prefix or better consider some other design pattern.

If you still like to have bean per country, I would suggest another approach. Introduce a registry service to get a required service by country code:

@Service
public class CaseServices {

  private final Map<String, CaseService> servicesByCountryCode = new HashMap<>();

  @Autowired
  public CaseServices(List<CaseService> services){
    for (CaseService service: services){
      register(service.getCountryCode(), service);
    }
  }

  public void register(String countryCode, CaseService service) {
    this.servicesByCountryCode.put(countryCode, service);
  }

  public CaseService getCaseService(String countryCode){
    return this.servicesByCountryCode.get(countryCode);
  }
}

Example usage:

@Service
public class DoService {

  @Autowired CaseServices caseServices;

  public void doSomethingWith(Case case){
    CaseService service = caseServices.getCaseService(case.getCountryCode());
    service.modify(case);
  }
}

In this case you have to add String getCountryCode() method to your CaseService interface.

public interface CaseService {
    void modify(Case case);
    String getCountryCode();
}

Alternatively, you can add method CaseService.supports(Case case) to select the service. Or, if you cannot extend the interface, you can call CaseServices.register(String, CaseService) method from some initialiser or a @Configuration class.

UPDATE: Forgot to mention, that Spring already provides a nice Plugin abstraction to reuse boilerplate code for creating PluginRegistry like this.

Example:

public interface CaseService extends Plugin<String>{
    void doSomething(Case case);
}

@Service
@Priority(0)
public class SwissCaseService implements CaseService {

  void doSomething(Case case){
    // Do something with the Swiss case
  }

  boolean supports(String countryCode){
    return countryCode.equals("CH");
  }
}

@Service
@Priority(Ordered.LOWEST_PRECEDENCE)
public class DefaultCaseService implements CaseService {

  void doSomething(Case case){
    // Do something with the case by-default
  }

  boolean supports(String countryCode){
    return true;
  }
}

@Service
public class CaseServices {

  private final PluginRegistry<CaseService<?>, String> registry;

  @Autowired
  public Cases(List<CaseService> services){
    this.registry = OrderAwarePluginRegistry.create(services);
  }

  public CaseService getCaseService(String countryCode){
    return registry.getPluginFor(countryCode);
  }
}

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