使用session技术来实现网上商城购物车的功能
首先、简单的了解session和cookie的区别：
一、session和cookie的区别：
session是把用户的首写到用户独占的session中（服务器端）
cookie是把用户的数据写给用户的浏览器。
session对象由服务器创建，开发人员可以调用request对象的getsession方法得到session对象。
首先写页面代码，仍然借助于商品浏览记录来写：
1、jsp购买页面代码如下：
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@page import="java.util.*"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>购物页面</title>
</head>
<body>
<h1>商品列表</h1>
<ul >
<li><a href="/myday07/addcookie?id=1">java基础</a><a href="/myday07/buysession?id=1">购买</a></li>
<li><a href="/myday07/addcookie?id=2">javaweb</a><a href="/myday07/buysession?id=2">购买</a></li>
<li><a href="/myday07/addcookie?id=3">DHTML</a><a href="/myday07/buysession?id=3">购买</a></li>
<li><a href="/myday07/addcookie?id=4">数据库</a><a href="/myday07/buysession?id=4">购买</a></li>
<li><a href="/myday07/addcookie?id=5">Struts</a><a href="/myday07/buysession?id=5">购买</a></li>
<li><a href="/myday07/addcookie?id=6">Spring</a><a href="/myday07/buysession?id=6">购买</a></li>
<li><a href="/myday07/addcookie?id=7">Hibernate</a><a href="/myday07/buysession?id=7">购买</a></li>
</ul>
<h1>最近访问记录</h1><h5><a href="/myday07/clearcookie">清空数据</a> </h5>
<%
String[] arr = {"java基础","javaweb","DHTML","数据库","Struts","Spring","Hibernate"};
// 获得所有cookie
Cookie[] cookies = request.getCookies();
// 在cookie中查找商品浏览记录
String visitlist = null;
if(cookies!=null){
for (Cookie cookie : cookies) {
if (cookie.getName().equals("visitlist")) {
visitlist = cookie.getValue();
break;
}
}
if(visitlist==null){ // 商品列表不存在
out.println("无");
}else{
String[] existIds = visitlist.split(",");
for(String existId:existIds){
int id = Integer.parseInt(existId);
out.println(arr[id-1]+"<br/>");
}
}
}
%>
<hr>
<h1>购物车列表</h1>
<%
//1.获得购物车列表
Map<String, Integer> cart=(Map<String, Integer>)session.getAttribute("cart");
//2.遍历map输出
if(cart!=null){
Set<String> keys=cart.keySet();
for(String id:keys)
{
int number=cart.get(id);//每件商品的数量
int idInt=Integer.parseInt(id);
String productName=arr[idInt-1];
out.println("商品名称:"+productName+",商品数量："+number+"<br/>");
}
}
%>
<hr/>
</body>
</html>
2、编写商品浏览记录的servlet页面
package cn.itcast.cookie;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class addCookie extends HttpServlet {
// 获得用户当前访问商品，更新到商品浏览记录列表
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 自动刷新
response.setHeader("refresh", "2;url=/myday07/products1.jsp");
// 1、获得当前用户浏览商品id
String id = request.getParameter("id");
// 2、获得用户浏览记录列表
Cookie[] cookies = request.getCookies();
// 查找访问记录列表 name:visitlist ----- 1,3,5,6
String visitlist = null;
if (cookies != null) { // 存在cookie
for (Cookie cookie : cookies) {
if (cookie.getName().equals("visitlist")) {
visitlist = cookie.getValue();
break;
}
}
if (visitlist == null) {
// 列表不存在,当前商品第一件商品
Cookie cookie = new Cookie("visitlist", id);
cookie.setMaxAge(60 * 60);
response.addCookie(cookie);
response.getWriter().println("add success");
} else {
// 3、判断当前商品是否已经在列表中
String[] existIds = visitlist.split(",");
for (String exsitId : existIds) {
if (exsitId.equals(id)) { // id存在在列表中
response.getWriter().println("add success");
return;
}
}
// 4、如果当前商品不在列表中，添加到列表
Cookie cookie = new Cookie("visitlist", visitlist + "," + id);
cookie.setMaxAge(60 * 60);
response.addCookie(cookie);
response.getWriter().println("add success");
}
} else {
// 表示 并没有该站点的任何cookie
Cookie cookie = new Cookie("visitlist", id);
cookie.setMaxAge(60 * 60);
response.addCookie(cookie);
response.getWriter().println("add success");
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
3、编写清除缓存的cookie页面
package cn.itcast.cookie;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class clearCookie extends HttpServlet
{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
Cookie cookie=new Cookie("visitlist","");
cookie.setMaxAge(0);
response.addCookie(cookie);
response.sendRedirect("/myday07/products1.jsp");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
doGet(request, response);
}
}
4、编写商品购买页面
package cn.itcast.cookie;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
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 BuySession extends HttpServlet
{
//添加商品到购物车
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
//1.获得商品的id
String id=request.getParameter("id");
//2.获得购物车cart--从session得到
HttpSession session=request.getSession();
Map<String, Integer> cart=(Map<String, Integer>)session.getAttribute("cart");//如果session中没有购物车呢
if(cart==null)
{//原来的session中并不存在购物车
cart=new HashMap<String, Integer>();
}
//3.判断商品是否存在购物车中
if(cart.containsKey(id))
{
//4.存在数量+1
int number=cart.get(id);
cart.put(id, number+1);
}else{
//5.不存在 将商品存入购物车 数量1
cart.put(id, 1);
}
session.setAttribute("cart", cart);
response.sendRedirect("/myday07/products1.jsp");//重定向回去
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
doGet(request, response);
}
}
最终效果如下：
