Java使用cookie显示最近查看过的书分享

  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);   }