1、在DisPlay的servlet中主要做两件事情
1.1显示在出售的商品
1.2显示顾客曾经浏览的商品
DisPlay的代码如下：
package com.baowei.cookie; import java.io.IOException; import java.io.PrintWriter; import java.util.Iterator; import java.util.Map; import java.util.Map.Entry; import java.util.Set; 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 Display extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { resp.setCharacterEncoding("utf-8"); resp.setContentType("text/html;charset=utf-8"); //显示所有的图书 PrintWriter out = resp.getWriter(); out.print("本书店出售的图书如下:<br/>"); Map<String,Book> books = DB.getDBMap(); Set<Entry<String, Book>> set = books.entrySet(); Iterator<Entry<String, Book>> it = set.iterator(); while(it.hasNext()){ Entry<String, Book> entry = it.next(); Book book = entry.getValue(); out.print("<a href='/HuiHuaTest/BookDetail?id="+book.getId()+"' target='_blank'>"+book.getName()+"</a><br/>"); } //用户最近看过的图书 out.print("你最近浏览过的图书如下:<br/>"); Cookie cookie = null; Cookie [] cookies = req.getCookies(); for (int i = 0; cookies != null && i < cookies.length; i++) { if(cookies[i].getName().equals("bookHistory")){ cookie = cookies[i]; } } if(cookie!=null){ //找到了bookHistory这个cookie String bookHistory = cookie.getValue(); //4_6_1 String ids[] = bookHistory.split("\_"); //这样划分更好 for(String id: ids){ Book book = (Book) DB.getDBMap().get(id); out.print(book.getName() + "<br/>"); } } } }
2. 对于图书的详细介绍的BookDetail的servlet，也是两个功能
2.1 介绍商品的详细信息
2.2 将浏览过的商品的信息加入到Cookie中，并且将Cookie写回浏览器
BookDetail的实现代码如下：
1 package com.baowei.cookie; 2 3 import java.io.IOException; 4 import java.io.PrintWriter; 5 import java.util.Arrays; 6 import java.util.LinkedList; 7 8 import javax.servlet.ServletException; 9 import javax.servlet.http.Cookie; 10 import javax.servlet.http.HttpServlet; 11 import javax.servlet.http.HttpServletRequest; 12 import javax.servlet.http.HttpServletResponse; 13 14 public class BookDetail extends HttpServlet { 15 16 public void doGet(HttpServletRequest request, HttpServletResponse response) 17 throws ServletException, IOException { 18 19 doPost(request, response); 20 21 } 22 23 public void doPost(HttpServletRequest request, HttpServletResponse response) 24 throws ServletException, IOException { 25 26 response.setContentType("text/html;charset=UTF-8"); 27 response.setCharacterEncoding("UTF-8"); 28 PrintWriter out = response.getWriter(); 29 30 // 1.根据用户带过来的id值，显示相应商品的信息 31 out.print("您想看的书的详细信息为：<br/>"); 32 String id = request.getParameter("id"); 33 Book book = (Book) DB.getDBMap().get(id); 34 out.print(book.getId() + "<br/>"); 35 out.print(book.getName() + "<br/>"); 36 out.print(book.getAuthor() + "<br/>"); 37 38 // 2.以cookie的形式回写该商品的id号给浏览器 39 String bookHistory = makeCookie(book.getId(), request); 40 Cookie cookie = new Cookie("bookHistory", bookHistory); 41 //cookie.setMaxAge(10000); //将Cookie保存在硬盘内 42 response.addCookie(cookie); 43 44 } 45 46 // 根据用户原来看过的书，以及现在看的书的id，构建新的cookie值 47 private String makeCookie(String id, HttpServletRequest request) { 48 49 // bookHistory=null 3 bookHistory=3 50 // bookHistory=2_1_5 3 bookHistory=3_2_1 51 // bookHistory=2 3 3 bookHistory=3_2 52 // bookHistory=2_3 3 bookHistory=3_2 53 54 // 1.得到用户曾经看过的书 55 String bookHistory = null; 56 Cookie cookies[] = request.getCookies(); 57 for (int i = 0; cookies != null && i < cookies.length; i++) { 58 if (cookies[i].getName().equals("bookHistory")) { 59 bookHistory = cookies[i].getValue(); 60 } 61 } 62 63 if (bookHistory == null) { 64 bookHistory = id; 65 return bookHistory; 66 } 67 68 // bookHistory=1_2_5 代表用户曾经看一些书，接着程序要得到用户曾经看过什么书 69 String ids[] = bookHistory.split("_"); 70 // 为了检测数组中是否包含当前id，我们应该把数据转成集合，并且还要转成链表结构的集合 71 LinkedList<String> idList = new LinkedList(Arrays.asList(ids)); 72 73 if (idList.contains(id)) { 74 idList.remove(id); 75 } else { 76 if (idList.size() >= 5) { 77 idList.removeLast(); 78 } 79 } 80 idList.addFirst(id); 81 82 StringBuffer sb = new StringBuffer(); 83 for (String lid : idList) { // 1_2_3_ 84 sb.append(lid + "_"); 85 } 86 87 return sb.deleteCharAt(sb.length() - 1).toString(); 88 } 89 90 }
上面两个程序中用到的Book类和DB类如下：
Book类的代码：
1 package com.baowei.cookie; 2 3 public class Book { 4 5 private String id; 6 private String name; 7 private String author; 8 9 public Book() { 10 11 } 12 13 public Book(String id, String name, String author) { 14 this.id = id; 15 this.name = name; 16 this.author = author; 17 } 18 public String getId() { 19 return id; 20 } 21 public void setId(String id) { 22 this.id = id; 23 } 24 public String getName() { 25 return name; 26 } 27 public void setName(String name) { 28 this.name = name; 29 } 30 public String getAuthor() { 31 return author; 32 } 33 public void setAuthor(String author) { 34 this.author = author; 35 } 36 37 38 39 }
DB类的代码如下：
package com.baowei.cookie; import java.util.HashMap; import java.util.Map; public class DB { static Map<String,Book> map = new HashMap<String,Book>(); static { map.put("1", new Book("1","JavaWeb开发","张保卫") ); map.put("2", new Book("2","操作系统","张保卫") ); map.put("3", new Book("3","Spring开发","张保卫") ); map.put("4", new Book("4","Struts2开发","张保卫") ); map.put("5", new Book("5","Java基础开发","张保卫") ); map.put("6", new Book("6","数据结构","张保卫") ); map.put("7", new Book("7","ACM","张保卫") ); map.put("8", new Book("8","计算机网络","张保卫") ); map.put("9", new Book("9","软件工程","张保卫") ); map.put("10", new Book("10","Android开发","张保卫") ); } public static Map<String,Book> getDBMap(){ return map; } }