关于用户浏览商品的历史记录（cookie）

创建对象：用集合模拟数据库：创建一个简单的内容显示界面

<pre name="code" class="java">package com.cn.cookie;import java.io.IOException;import java.io.PrintWriter;import java.util.LinkedHashMap;import java.util.Map;import javax.servlet.ServletException;import javax.servlet.http.Cookie;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;@SuppressWarnings("serial")public class Cookie1 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//1.创建所有商品信息response.setCharacterEncoding("UTF-8");response.setContentType("text/html;charset = UTF-8");PrintWriter out = response.getWriter();out.print("<center>");out.print("所有的商品信息:<br>");Map<String, Goods> map = Db.getAll();for(Map.Entry<String, Goods> entry:map.entrySet()){Goods goods = entry.getValue();out.print("<a href = '/Userinfo/Cookie2?id="+goods.getId()+"'targent = '_blank'>"+goods.getName()+"</a><br>");}out.print("</center>");//2.显示用户曾经浏览过的商品out.print("你浏览过的商品为：<br>");Cookie cookies[] = request.getCookies();for(int i=0;cookies != null && i<cookies.length;i++){if(cookies[i].getName().equals("goodsHistory")){String ids[] = cookies[i].getValue().split("\\,");for(String id :ids){Goods goods = (Goods) Db.getAll().get(id);out.print("<a href = '/Userinfo/Cookie2?id="+goods.getId()+"'targent = '_blank'>"+goods.getName()+"</a><br/>");}}}}/** * 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 {doGet(request, response);}} class Db{private static Map<String , Goods> map = new LinkedHashMap();static {map.put("1",new Goods("1","红楼梦","曹雪芹","中国经典名著 "));map.put("2",new Goods("2","javaweb开发","白光元","javaweb自学书籍"));map.put("3",new Goods("3","西游记","吴承恩","中国经典名著"));map.put("4",new Goods("4","童年","高尔基","俄国经典名著"));map.put("5",new Goods("5","鲁滨逊漂流记","迪福","英国名著"));map.put("6",new Goods("6","java核心技术","马志强","java教科书"));map.put("7",new Goods("7","javaweb完全自学手册","宝柏","javaweb开发宝典"));map.put("8",new Goods("8","动态网站开发","萧萧","javaweb书籍"));}public static Map getAll(){return map;}}class Goods{private String id ;private String name;private String author;private String description;public Goods() {super();// TODO Auto-generated constructor stub}public Goods(String id, String name, String author, String description) {super();this.id = id;this.name = name;this.author = author;this.description = description;}public String getId() {return id;}public void setId(String id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getAuthor() {return author;}public void setAuthor(String author) {this.author = author;}public String getDescription() {return description;}public void setDescription(String description) {this.description = description;}}

创建cookie；利用返回id显示商品的信息，并且保存在cookie的集合中：最后通过遍历的得到最近浏览的商品；

<pre name="code" class="java">package com.cn.cookie;import java.io.IOException;import java.io.PrintWriter;import java.util.Arrays;import java.util.LinkedList;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 Cookie2 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//根据用户带来的id，显示商品的详细信息response.setContentType("text/html;charset=utf-8");response.setCharacterEncoding("UTF-8");PrintWriter out = response.getWriter();String id =request.getParameter("id");Goods goods = (Goods) Db.getAll().get(id);out.write(goods.getId()+"<br/>");out.write(goods.getName()+"<br/>");out.write(goods.getAuthor()+"<br/>");out.write(goods.getDescription()+"<br/>");//构建cookie，回写给浏览器String cookieValue = buildCookie(id,request);Cookie cookie = new Cookie("goodsHistory",cookieValue);cookie.setMaxAge(1*30*24*3600);cookie.setPath("/Userinfo");response.addCookie(cookie);out.print("<a href = '/Userinfo/Cookie1'>返回首页</a>");}private String buildCookie(String id, HttpServletRequest request) {String goodsHistory = null;Cookie cookies[] =request.getCookies();for(int i = 0;cookies!=null&&i<cookies.length;i++){if(cookies[i].getName().equals("goodsHistory")){goodsHistory = cookies[i].getValue();}}if(goodsHistory ==null){return id;}LinkedList<String> list =new LinkedList(Arrays.asList(goodsHistory.split("\\,")));if(list.contains(id)){list.remove(id);list.addFirst(id);}else{if(list.size()>=3){list.removeLast();list.addFirst(id);}else{list.addFirst(id);}}StringBuilder sb =new StringBuilder();for(String bid:list){sb.append(bid+",");}return sb.deleteCharAt(sb.length()-1).toString();}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}