只写了一遍的代码：页面的跳转操作，全部是从web文件中读取进行的
web配置文件
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
demo
com.it.Demo
demo
/CarServlet
demo1
com.it.ClearDemo
demo1
/ClearCartServlet
public class Demo extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
HttpSession session = req.getSession();
resp.setContentType("text/html;charset=utf-8");
int id = Integer.parseInt(req.getParameter("id"));
String[] names = {"iphone7", "小米6", "三星note8", "魅族", "华为9"};
String name = names[id];
// 先拿map对象，如果没有值默认为null
Map cartMap = (Map) session.getAttribute("cart");
// 根据这个对象，判断是否是第一次进来
if (cartMap == null) {
cartMap = new HashMap();
// 如果是第一次进来，就添加一个map对象
session.setAttribute("cart", cartMap);
}
// 判断这个map对象中是否存在手机名称的键
if (cartMap.containsKey(name)) {
cartMap.put(name, cartMap.get(name) + 1);
} else {
cartMap.put(name, 1);
}
System.out.println(cartMap);
继续浏览
");
去购物车结算
");
}
}
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
首页获取session中的map对象，讲值取出来
Created by IntelliJ IDEA.
User: maotouying
Date: 2019/11/4
Time: 12:53
To change this template use File | Settings | File Templates.
--%>
购物车您的购物车商品如下：
Map map= (Map)session.getAttribute("cart");
// 遍历map
if (map != null){
for (String key: map.keySet()){
int value = map.get(key);
%>
名称： 数量：
}
}
%>
清空购物车
清除session中的值，清空购物车
public class ClearDemo extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
HttpSession session = req.getSession();
// 使会话失效
session.invalidate();
resp.sendRedirect("cart.jsp");
}
}