Spring in practice : REST service(EN)

public class WindowDto {
    private Long id;
    private String name;
    private WindowStatus windowStatus;
    private String roomName;
    private Long roomId;

    public WindowDto() {
    }

    public WindowDto(Window window) {
        this.id = window.getId();
        this.name = window.getName();
        this.windowStatus = window.getWindowStatus();
        this.roomName = window.getRoom().getName();
        this.roomId = window.getRoom().getId();
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public WindowStatus getWindowStatus() {
        return windowStatus;
    }

    public void setWindowStatus(WindowStatus windowStatus) {
        this.windowStatus = windowStatus;
    }

    public String getRoomName() {
        return roomName;
    }

    public void setRoomName(String roomName) {
        this.roomName = roomName;
    }

    public Long getRoomId() {
        return roomId;
    }

    public void setRoomId(Long roomId) {
        this.roomId = roomId;
    }
}

@RestController // (1)
@RequestMapping("/api/windows") // (2)
@Transactional // (3)
public class WindowController {

    private final WindowDao windowDao;
    private final RoomDao roomDao;

    public WindowController(WindowDao windowDao, RoomDao roomDao) { // (4)
        this.windowDao = windowDao;
        this.roomDao = roomDao;
    }

    @GetMapping // (5)
    public List<WindowDto> findAll() {
        return windowDao.findAll().stream().map(WindowDto::new).collect(Collectors.toList());  // (6)
    }

    @GetMapping(path = "/{id}")
    public WindowDto findById(@PathVariable Long id) {
        return windowDao.findById(id).map(WindowDto::new).orElse(null); // (7)
    }

    @PutMapping(path = "/{id}/switch")
    public WindowDto switchStatus(@PathVariable Long id) {
        Window window = windowDao.findById(id).orElseThrow(IllegalArgumentException::new);
        window.setWindowStatus(window.getWindowStatus() == WindowStatus.OPEN ? WindowStatus.CLOSED: WindowStatus.OPEN);
        return new WindowDto(window);
    }

    @PostMapping // (8)
    public WindowDto create(@RequestBody WindowDto dto) {
        // WindowDto must always contain the window room
        Room room = roomDao.getById(dto.getRoomId());
        Window window = null;
        // On creation id is not defined
        if (dto.getId() == null) {
            window = windowDao.save(new Window(room, dto.getName(), dto.getWindowStatus()));
        }
        else {
            window = windowDao.getById(dto.getId());  // (9)
            window.setWindowStatus(dto.getWindowStatus());
        }
        return new WindowDto(window);
    }

    @DeleteMapping(path = "/{id}")
    public void delete(@PathVariable Long id) {
        windowDao.deleteById(id);
    }
}