java-ajax与mysql五表联动2----商品管理

@WebServlet("/admin/goods/*")
public class GoodsServlet extends HttpServlet {
    private GoodsService goodsService = new GoodsServiceImpl();
 
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String uri = req.getRequestURI(); // 获取请求URI
        String action = uri.substring(uri.lastIndexOf("/") + 1); // 获取操作指令
 
        switch (action) {
            case "list":
                list(req, resp);
                break;
            case "toAdd":
                toAdd(req, resp);
                break;
            case "add":
                add(req, resp);
                break;
            case "toEdit":
                toEdit(req, resp);
                break;
            case "edit":
                edit(req, resp);
                break;
            case "del":
                del(req, resp);
                break;
            default:
                list(req, resp);
                break;
        }
    }
 
    private void list(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        List<Goods> goodsList = goodsService.listGoods();
        req.setAttribute("goodsList", goodsList);
        req.getRequestDispatcher("/admin/goods/list.jsp").forward(req, resp);
    }
 
    private void toAdd(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 获取所有一级分类
        List<Category> categoryList = CategoryService.listCategory();
        req.setAttribute("categoryList", categoryList);
        // 获取所有品牌
        List<Brand> brandList = BrandService.listBrand();
        req.setAttribute("brandList", brandList);
        // 获取所有供应商
        List<Provider> providerList = ProviderService.listProvider();
        req.setAttribute("providerList", providerList);
        // 获取所有单位
        List<Unit> unitList = UnitService.listUnit();
        req.setAttribute("unitList", unitList);
        // 获取所有特征
        List<Feature> featureList = FeatureService.listFeature();
        req.setAttribute("featureList", featureList);
        req.getRequestDispatcher("/admin/goods/add.jsp").forward(req, resp);
    }
 
    private void add(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        String name = req.getParameter("name");
        String categoryId = req.getParameter("categoryId");
        String brandId = req.getPa