实现简单的购物车

package com.yidu.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class BuyServlet extends HttpServlet {

 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  /*
   * 购物车用session保存
   */
  HttpSession session=request.getSession();
  Object obj= session.getAttribute("shopCar");
  //判断是否是第一次
  if(obj==null){
   ArrayList list=new ArrayList();
   list.add(request.getParameter("item"));
   obj=list;
   session.setAttribute("shopCar", obj);
  }
  else{
   ArrayList list=(ArrayList)obj;
   list.add(request.getParameter("item"));
   session.setAttribute("shopCar", list);
  }
  response.sendRedirect("display.jsp");
  
 }

 
 public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

 }

}

 

package com.yidu.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class LoginServlet extends HttpServlet {

 /**
  * The doGet method of the servlet. <br>
  *
  * This method is called when a form has its tag value method equals to get.
  *
  * @param request the request send by the client to the server
  * @param response the response send by the server to the client
  * @throws ServletException if an error occurred
  * @throws IOException if an error occurred
  */
 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  
  HttpSession session=request.getSession();
  session.setAttribute("userName", request.getParameter("userName"));
//  this.getServletContext().setAttribute("userName", request.getParameter("userName"));
//  request.getRequestDispatcher("/MyJsp.jsp").forward(request, response);
  
  String url=response.encodeRedirectUrl("/chapter6/MyJsp.jsp");
//  System.out.println(url);
  response.sendRedirect(url);
 }

 /**
  * The doPost method of the servlet. <br>
  *
  * This method is called when a form has its tag value method equals to post.
  *
  * @param request the request send by the client to the server
  * @param response the response send by the server to the client
  * @throws ServletException if an error occurred
  * @throws IOException if an error occurred
  */
 public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

 }

}