把购买数据添加到购物车

这里用map存放购买信息，键值对为 产品信息，和购买数量

@RequestMapping("/addCart.do")
    public String addCart(Product product,HttpSession session,Model model){
        product=productService.findProductById(product.getId());
        Map<Product,Integer> carts= (Map<Product, Integer>) session.getAttribute("carts");
        if(carts==null){
          carts=  new HashMap<Product,Integer>();
        }
        Integer count = (Integer)carts.get(product);
        if(count==null){
            carts.put(product, new Integer(1));
        }else if(count==product.getPnum()){

            model.addAttribute("fail","购买商品达到上限,无法继续购买！");
            return "/client/cart.jsp";
        }else{
            carts.put(product,count+1);
        }
        session.setAttribute("carts",carts);
        return "/client/cart.jsp";
    }
        @RequestMapping("/changeCart.do")
        public String changeCart(Integer id,Integer count,HttpSession session){
            Product product=productService.selectProductById(id);
            Map<Product,Integer> carts= (Map<Product, Integer>) session.getAttribute("carts");
            if(count==0){
                carts.remove(product);
            }else{
                carts.put(product,count);
            }
            return "/client/cart.jsp";
        }