Cookie实现:您曾经浏览过的商品记录

1、CookieHistoryDemo1.java代码实现如下：

    import java.io.IOException;  
    import java.io.PrintWriter;  
    import java.util.Map;  
    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 CookieHistoryDemo1 extends HttpServlet {  
        public void doGet(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
            response.setContentType("text/html;charset=UTF-8");  
            PrintWriter out = response.getWriter();  
            // 1.显示网站所有商品  
            out.write("本网站有如下书籍：<br><br>");  
            Set<Map.Entry<String, Book>> set=DB.getAll().entrySet();  
            for(Map.Entry<String, Book> me : set){  
                Book  book= me.getValue();  
                out.write("<a href='/MyWebStart/servlet/CookieHistoryDemo2?id="+book.getId()+"' target='_blank'>"+book.getName()+"</a>");  
                out.write("<br/>");  
                  
            }  
            //2.显示用户曾经浏览过的商品  
            out.write("<br/><br/>您曾经浏览过的商品:<br/>" );  
            Cookie cookies[] = request.getCookies();  
            for(int i=0;cookies!=null && i<cookies.length;i++){  
                Cookie cookie = cookies[i];  
                if(cookie.getName().equals("bookHistory")){  
                    String bookHistory = cookie.getValue();  //  2_3  
                    String ids[] = bookHistory.split("\\_");  //[2,3]  
                    for(String id: ids){  
                        Book book = (Book) DB.getAll().get(id);  
                        out.write(book.getName() + "<br/>");  
                    }  
                }  
            }  
        }  
      
        public void doPost(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
      
            doGet(request, response);  
        }  
      
    }  

2,CookieHistoryDemo2.java

    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;  
      
      
      
    public class CookieHistoryDemo2 extends HttpServlet {  
        public void doGet(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
            response.setContentType("text/html;charset=UTF-8");  
            PrintWriter out = response.getWriter();  
            //1.根据用户带过来的id号，显示商品的详细信息  
            String id = request.getParameter("id");  
            Book book = (Book) DB.getAll().get(id);  
              
            out.write("您要查看的书的详细信息如下：<br/><br/>");  
            out.write(book.getId() + "<br/>");      
            out.write(book.getName() + "<br/>");  
            out.write(book.getAuthor() + "<br/>");  
            out.write(book.getDescription() + "<br/>");  
            //2.给用户回送包含当前商品id的cookie  
            String bookHistory = makeHistory(request,id);    //  3_2  
            Cookie cookie = new Cookie("bookHistory",bookHistory);  
            cookie.setMaxAge(1*30*24*3600);  
              
            response.addCookie(cookie);  
        }  
      
        private String makeHistory(HttpServletRequest request, String id) {  
            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();  
                }  
            }  
              
            //  bookHistory=null      1    bookHistory=1  
            //  bookHistory=3_1_5     1    bookHistory=1_3_5  
            //  bookHistory=3_2_5     1    bookHistory=1_3_2  
            //  bookHistory=3_2       1    bookHistory=1_3_2  
              
              
            //  bookHistory=null      1    bookHistory=1  
            if(bookHistory==null){  
                return id;  
            }  
              
            List l = Arrays.asList(bookHistory.split("\\_"));   //[3,4]  //数组  链接  
            LinkedList<String> list = new  LinkedList();  
            list.addAll(l);  
              
            if(list.contains(id)){  
                //  bookHistory=3_1_5     1    bookHistory=1_3_5  
                list.remove(id);  
                list.addFirst(id);  
            }else{  
                if(list.size()>=3){  
                    //  bookHistory=3_2_5     1    bookHistory=1_3_2  
                    list.removeLast();  
                    list.addFirst(id);  
                }else{  
                    //  bookHistory=3_2       1    bookHistory=1_3_2  
                    list.addFirst(id);  
                }  
            }  
              
            StringBuffer sb = new StringBuffer();  //2_3_4  
            for(String lid: list){  
                sb.append(lid + "_");  
            }  
              
            return sb.deleteCharAt(sb.length()-1).toString();  
        }  
      
        public void doPost(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
      
            doGet(request, response);  
        }  

3,DB.java

    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","Job","New book"));  
            map.put("2", new Book("2","spring","Hitpop","Good book"));  
            map.put("3", new Book("3","hibernate","Brucec","Nice book"));  
            map.put("4", new Book("4","struts","Smith","Pass book"));  
            map.put("5", new Book("5","ajax","Zhangli","Hand book"));  
        }  
          
        public static Map getAll(){  
            return map;  
        }  
    }  

4,Book.java

    public class Book {  
        private String id;  
        private String name;  
        private String author;  
        private String description;  
        public Book() {  
            super();  
            // TODO Auto-generated constructor stub  
        }  
        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;  
        }  
      
    }