Spring Boot

// REST API 컨트롤러 예제 - Spring Boot 3.3
@RestController
@RequestMapping("/api/users")
@RequiredArgsConstructor  // Lombok: 생성자 주입
public class UserController {

    private final UserService userService;

    // GET /api/users
    @GetMapping
    public List<UserDto> getAllUsers() {
        return userService.findAll();
    }

    // GET /api/users/{id}
    @GetMapping("/{id}")
    public ResponseEntity<UserDto> getUserById(
            @PathVariable Long id) {
        return userService.findById(id)
            .map(ResponseEntity::ok)
            .orElse(ResponseEntity.notFound().build());
    }

    // POST /api/users
    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public UserDto createUser(
            @Valid @RequestBody CreateUserRequest request) {
        return userService.create(request);
    }

    // DELETE /api/users/{id}
    @DeleteMapping("/{id}")
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public void deleteUser(@PathVariable Long id) {
        userService.delete(id);
    }
}

// 서비스 계층 - 의존성 주입(DI) 예제
@Service
@Transactional(readOnly = true)
@RequiredArgsConstructor
public class UserService {

    // 생성자 주입 (권장 방식)
    private final UserRepository userRepository;
    private final PasswordEncoder passwordEncoder;
    private final UserMapper userMapper;

    public List<UserDto> findAll() {
        return userRepository.findAll()
            .stream()
            .map(userMapper::toDto)
            .toList();
    }

    public Optional<UserDto> findById(Long id) {
        return userRepository.findById(id)
            .map(userMapper::toDto);
    }

    @Transactional
    public UserDto create(CreateUserRequest request) {
        User user = User.builder()
            .email(request.email())
            .password(passwordEncoder.encode(request.password()))
            .name(request.name())
            .build();

        return userMapper.toDto(userRepository.save(user));
    }
}

// Repository - Spring Data JPA
public interface UserRepository
        extends JpaRepository<User, Long> {

    Optional<User> findByEmail(String email);

    @Query("SELECT u FROM User u WHERE u.status = :status")
    List<User> findByStatus(@Param("status") UserStatus status);
}