session实现购物车

购物车

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html; charset=UTF-8");
        //1.取到商品的对应id
        String ids = request.getParameter("id");
        int id = Integer.parseInt(ids);         //转成int类型
        //获取id对应的商品名称
        String [] names = {"iphone x","华为p20","三星s9","vivo nex","oppo find x"};
        String name = names[id];
        //2.获取session里存储的map数据
        Map<String,Integer> map = (Map<String, Integer>) request.getSession().getAttribute("cart");
        //如果map为空则表明session里没有放数据,则需要创建
        if(map==null) {
            map =new LinkedHashMap<String,Integer>();
            request.getSession().setAttribute("cart", map);
        }           
        //3.如果有则判断是否添加过该商品
            if(map.containsKey(name)) {
                map.put(name, map.get(name)+1);    //有该商品则数量加一
            }else {
                map.put(name, 1);                 //没有则添加
            }
        //4.跳转页面
        response.getWriter().write("<a href='product_list.jsp'><h2>继续购物<h2/><a/><br/>");
        response.getWriter().write("<a href='cart.jsp'><h2>去购物车结算<h2/><a/><br/>");

        }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        session.removeAttribute("cart");  
        response.sendRedirect("cart.jsp");

    }