How do I defining a bean type of this Mapper class?

Question

I want to know how can I register this Mapper class as a Spring bean. An entity called NormalBoard was designed, and an entity called ContestBoard that inherited it was designed and even Service Layer was created.

public class Mapper {

    private MenuRepository menuRepository;

    private ContestBoardServiceImpl contestBoardService;
    private NormalBoardServiceImpl normalBoardService;

    public BoardService findBoardServiceByMenuId(Integer menuId){
        MenuType menuType = menuRepository.findMenuTypeByMenuId(menuId).get();
        switch(menuType){
            case CONTEST:
                return contestBoardService;
            default:
                return normalBoardService;
        }
    }

I tried to search the menu according to the menuId value coming in requestParam from one controller and call the service layer method corresponding to the menu.

public class BoardController{
  private final Mapper mapper;

  @GetMapping
  public Page<Object> getBoardList(Pageable pageable, @RequestParam Integer menuId ) {
      return mapper.findBoardServiceByMenuId(menuId).getBoardList(menuId, pageable);
  }
}

This may be a silly way, but I came up with it because I don't want to design duplicate Controllers about NormalBoardController and ContestBoardController.

In this case, if you want to register Spring Bean for this Mapper class, what kind of annotation should be attached?