Cookie案例-显示商品浏览历史纪录

 package cn.itcast.cookie;

 import java.io.IOException;
 import java.io.PrintWriter;
 import java.util.Date;
 import java.util.HashMap;
 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;

 import cn.itcast.Book;
 import cn.itcast.Db;

 public class CookieDemo extends HttpServlet {

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

         response.setCharacterEncoding("UTF-8");
         response.setContentType("text/html;charset=UTF-8");
         PrintWriter out = response.getWriter();

         // 1.输出网站的商品
         out.write("本网站有如下商品：<br/>");
         Db db = new Db();
         Map<String, Book> map = db.getAll();

         for (Map.Entry<String, Book> entry : map.entrySet()) {
             Book book = entry.getValue();
             out.print("<a href='/ServletDemo/servlet/CookieDemo2?id="
                     + book.getId() + "'target='_blank'>" + book.getName()
                     + "</a><br/>");
         }

         // 2.显示用户曾经看过的商品
         out.print("<br/>您曾经看过如下商品：<br/>");
         Cookie cookies[] = request.getCookies();
         for (int i = 0; cookies != null && i < cookies.length; i++) {
             if (cookies[i].getName().equals("bookHistory")) {
                 String ids[] = cookies[i].getValue().split("\\,");
                 for(String id:ids){
                     Book book = (Book) Db.getAll().get(id);
                     out.print(book.getName()+"<br/>");
                 }
             }
         }

     }

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

     }

 }

 package cn.itcast.cookie;

 import java.io.IOException;
 import java.io.PrintWriter;
 import java.util.Arrays;
 import java.util.LinkedList;
 import java.util.List;

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

 import cn.itcast.Book;
 import cn.itcast.Db;

 public class CookieDemo2 extends HttpServlet {

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

         response.setCharacterEncoding("UTF-8");
         response.setContentType("text/html;charset=UTF-8");
         PrintWriter out = response.getWriter();

         // 1.给据用户带来的id，显示相应商品的详细信息。
         String id = request.getParameter("id");
         Book book = (Book) Db.getAll().get(id);
         out.write(book.getId() + "<br/>");
         out.write(book.getName() + "<br/>");
         out.write(book.getAuthor() + "<br/>");
         out.write(book.getDescription() + "<br/>");

         // 2.构建cookie，会写给浏览器
         String cookieValue = buildCookie(id, request);
         Cookie cookie = new Cookie("bookHistory", cookieValue);
         cookie.setMaxAge(1 * 30 * 24 * 60 * 60);
         cookie.setPath("/ServletDemo");
         response.addCookie(cookie);
     }

     private String buildCookie(String id, HttpServletRequest request) {

         String bookHistory = null;
         Cookie cookies[] = request.getCookies();
         for (int i = 0; cookies != null && i < cookies.length; i++) {
             if (cookies[i].getName().equals("bookHistory")) {
                 bookHistory = cookies[i].getValue();
             }

         }

         if (bookHistory == null) {
             return id;
         }

         LinkedList<String> list = new LinkedList(Arrays
                 .asList(bookHistory.split("\\,")));

         if (list.contains(id)) {
             list.remove(id);
         } else {
             if (list.size() >= 3) {
                 list.removeLast();
             }
         }

         list.addFirst(id);

         StringBuffer sb = new StringBuffer();
         for (String bid : list) {
             sb.append(bid+",");
         }

         return sb.deleteCharAt(sb.length()-1).toString();
     }

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

     }

 }

 package cn.itcast;

 import java.util.LinkedHashMap;
 import java.util.Map;

 public class Db {
     private static Map<String, Book> map = new LinkedHashMap();

     static{
         map.put("1", new Book("1","javaweb开发","Zero","一本好书！！"));
         map.put("2", new Book("2","jdbc开发","one","一本好书！！"));
         map.put("3", new Book("3","spring开发","two","一本好书！！"));
         map.put("4", new Book("4","struks开发","three","一本好书！！"));
         map.put("5", new Book("5","hibernate开发","four","一本好书！！"));
     }

     public static Map getAll(){
         return map;
     }
 }

 package cn.itcast;

 public class Book {
     private String id;
     private String name;
     private String author;
     private String description;

     public Book(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;
     }
 }