httpsession 少

package com.itheima.web;

import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import java.io.IOException; import java.util.ArrayList; import java.util.List;

/**

• 添加商品到购物车的Servlet */ @WebServlet("/addCart") public class AddCartServlet extends HttpServlet {

  @Override protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //1.解决乱码问题 req.setCharacterEncoding("UTF-8"); resp.setContentType("text/html;charset=UTF-8"); //2.获取请求参数 String productName = req.getParameter("product");

   //2.获取服务端的会话对象
   HttpSession session = req.getSession();
  
  
   //---------完善购物车的案例：-------------
   //看看是不是已经添加过商品到购物车了
   List<String> productInfo = (List<String>)session.getAttribute("productInfo");
   if(productInfo == null){
       //还没有添加商品到购物车，创建一个新的购物车
       productInfo = new ArrayList<>();
   }
   //把新的商品存到购物车里
   productInfo.add(productName);
   //----------完善购物车的案例：------------------
  
  
   //3.添加购物车集合到服务端会话对象的共享区域中
   session.setAttribute("productInfo",productInfo);//此时是把信息都添加到了服务器的内存之中。每个会话都有自己独立的内存空间
   //4.告知浏览器已经添加好了
   resp.getWriter().write("已经添加好了，可以查看购物车了。");
   resp.getWriter().write("<a href='/showCartInfo'>现在查看？</a>");
   resp.getWriter().write("<a href='/index.html'>回到主页</a>");
  

  } } ` package com.itheima.web;

import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import java.io.IOException; import java.util.List;

/**

• 用于从购物车中获取共享的信息 */ @WebServlet("/showCartInfo") public class ShowCartInfoServlet extends HttpServlet {

  /**

  • 获取共享的购物车信息
  • @param req
  • @param resp
  • @throws ServletException
  • @throws IOException */ @Override protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //1.解决乱码问题 req.setCharacterEncoding("UTF-8"); resp.setContentType("text/html;charset=UTF-8"); //2.获取会话对象 HttpSession session = req.getSession(); //3.使用会话对象获取共享数据 List productInfo = (List)session.getAttribute("productInfo"); //4.如果没有共享的购物车信息，就提示还没有添加 if(productInfo == null){ resp.getWriter().write("您还没有添加商品到购物车，现在添加？"); }else { //5.判断如果有共享的购物车信息，就输出 for (String productName : productInfo) { resp.getWriter().write("您添加的商品是："+productName+"
    "); } } } }

`