🌱 스프링의 DI 방법 (생성자 주입 VS 필드 주입)

@Service
public class StationConstructorService {
    private StationRepository stationRepository;

    public StationConstructorService(StationRepository stationRepository) {
        this.stationRepository = stationRepository;
    }

    public String sayHi() {
        return stationRepository.sayHi();
    }
}

@Service
public class StationFieldService {
    @Autowired
    private StationRepository stationRepository;

    public String sayHi() {
        return stationRepository.sayHi();
    }
}

@Service
public class StationSetterService {
    private StationRepository stationRepository;

    public String sayHi() {
        return stationRepository.sayHi();
    }

    @Autowired
    public void setStationRepository(StationRepository stationRepository) {
        this.stationRepository = stationRepository;
    }
}

@FunctionalInterface
public interface GameService {
    void gameMethod();
}

@Service
public class GameServiceImpl implements GameService {
    @Autowired
    private PieceService pieceService;

    @Override
    public void gameMethod() {
        pieceService.pieceMethod();
    }
}

@FunctionalInterface
public interface PieceService {
    void pieceMethod();
}

@Service
public class PieceServiceImpl implements PieceService {
    @Autowired
    private GameServiceImpl gameServiceImpl;

    @Override
    public void pieceMethod() {
        gameServiceImpl.gameMethod();
    }
}

@Service
public class GameServiceImpl implements GameService {
    private final PieceServiceImpl pieceService;

    public GameServiceImpl(PieceServiceImpl pieceService) {
        this.pieceService = pieceService;
    }

    @Override
    public void gameMethod() {
        pieceService.pieceMethod();
    }
}

@Service
public class PieceServiceImpl implements PieceService {
    private final GameServiceImpl gameServiceImpl;

    public PieceServiceImpl(GameServiceImpl gameServiceImpl) {
        this.gameServiceImpl = gameServiceImpl;
    }

    @Override
    public void pieceMethod() {
        gameServiceImpl.gameMethod();
    }
}