Java使用cookie显示最近查看过的书

import java.io.Serializable; public class Book implements Serializable { private String id; private String name; private String price; private String auth; private String publish; private String description;   public Book() { }   public Book(String id, String name, String price, String auth,   String publish, String description) {  super();  this.id = id;  this.name = name;  this.price = price;  this.auth = auth;  this.publish = publish;  this.description = description; }  public String getDescription() {  return description; }  public void setDescription(String description) {  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 getPrice() {  return price; } public void setPrice(String price) {  this.price = price; } public String getAuth() {  return auth; } public void setAuth(String auth) {  this.auth = auth; } public String getPublish() {  return publish; } public void setPublish(String publish) {  this.publish = publish; } }

import java.util.LinkedHashMap;import java.util.Map; import cn.huiyu.ben.Book;   public class BookDao { private static Map<String,Book> bookMap = new LinkedHashMap<String, Book>(); private BookDao() { } static{  bookMap.put("1", new Book("1","1111","11.0","zqwang","111出版社","111111111"));  bookMap.put("2", new Book("2","2222","22.0","zqwang","222出版社","222222222"));  bookMap.put("3", new Book("3","3333","33.0","zqwang","333出版社","333333333")); }   public static Map<String,Book> getBooks(){  return bookMap; }   public static Book getBook(String id){  return bookMap.get(id); }}

public void doGet(HttpServletRequest request, HttpServletResponse response)   throws ServletException, IOException {  response.setContentType("text/html;charset=utf-8");  //1.查询数据库中所有的书展示  Map<String,Book> map = BookDao.getBooks();  for(Map.Entry<String , Book> entry : map.entrySet()){   Book book = entry.getValue();   response.getWriter().write("<a href='"+request.getContextPath()+"/servlet/BookInfoServlet?id="+book.getId()+"'>"+book.getName()+"</a><br>");  }  response.getWriter().write("<hr>");     //2.显示之前看过的书  Cookie [] cs = request.getCookies();  Cookie findC = null;  if(cs!=null){   for(Cookie c : cs){    if("last".equals(c.getName())){     findC = c;    }   }  }  if(findC == null){   response.getWriter().write("没有看过任何书!");  }else{   response.getWriter().write("您曾经浏览过的书:<br>");   String[] ids = findC.getValue().split(",");   for(String id : ids){    Book book = BookDao.getBook(id);    response.getWriter().write(book.getName()+"<br>");   }  } }

public void doGet(HttpServletRequest request, HttpServletResponse response)   throws ServletException, IOException {  response.setContentType("text/html;charset=utf-8");  //1.获取要看的书的id,查询数据库找出书,输出书的详细信息  String id = request.getParameter("id");  Book book = BookDao.getBook(id);  if(book==null){   response.getWriter().write("找不到这本书!");   return;  }else{   response.getWriter().write("<h1>书名:"+book.getName()+"</h1>");   response.getWriter().write("<h3>作者:"+book.getAuth()+"</h3>");   response.getWriter().write("<h3>售价:"+book.getPrice()+"</h3>");   response.getWriter().write("<h3>出版社:"+book.getPublish()+"</h3>");   response.getWriter().write("<h3>描述信息:"+book.getDescription()+"</h3>");  }     //2.发送cookie保存最后看过的书  // --- 1 --> 1  // 1 --2,1 --> 2,1  // 2,1--3,2,1 --> 3,2,1  // 3,2,1 -- 4,3,2 --> 4,3,2  // 4,3,2 --3,4,2 --> 3,4,2  String ids = "";     Cookie [] cs = request.getCookies();  Cookie findC = null;  if(cs!=null){   for(Cookie c : cs){    if("last".equals(c.getName())){     findC = c;    }   }  }     if(findC == null){   //说明之前没有看过书的记录   ids += book.getId();  }else{   //说明之前有历史看过的书的记录,需要根据历史记录算一个新的记录出来   String [] olds = findC.getValue().split(",");    StringBuffer buffer = new StringBuffer();   buffer.append(book.getId()+",");   for(int i = 0;i<olds.length && buffer.toString().split(",").length<3 ;i++){    String old = olds[i];    if(!old.equals(book.getId())){     buffer.append(old+",");    }   }   ids = buffer.substring(0, buffer.length()-1);  }           Cookie lastC = new Cookie("last",ids);  lastC.setMaxAge(3600*24*30);  lastC.setPath(request.getContextPath());  response.addCookie(lastC); }