some questions about "Beverage Buddy App for Vaadin Flow"

	@Autowired
    private CategoryService categoryService;

    @Autowired
    private ReviewService reviewService;

    private final TextField searchField = new TextField("", "Search categories");
    private final H2 header = new H2("Categories");
    private final Grid<Category> grid = new Grid<>();

    private CategoryEditorDialog form;
    public CategoriesList() {
        form = new CategoryEditorDialog(
                this::saveCategory, this::deleteCategory, this.categoryService, reviewService);
        initView();

        addSearchBar();
        addContent();

        updateView(categoryService);
    }

when I want to use springDataJpa + herbernate to persist data in mysql in this demo , I found it failed. because when i access the url localhost:8080 in Chrome , the Class CategoriesList create a new instance,but it will occur nullpointerException,the categoryService and reviewService will be null. So how could I set the origin data queried from the database when initialize the instance?

Beverage Buddy App for Vaadin Flow could see in [https://vaadin.com/start/lts/simple-ui]
(http://)