Cookie的应用：显示用户上次浏览过的商品

ShowAllBooksServlet.java文件：

package com.itheima.cookie.app3;import java.io.IOException;import java.io.PrintWriter;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;//显示所有的商品，提供查看详细内容的链接//显示最近的浏览记录：3条public class ShowAllBooksServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        response.setContentType("text/html;charset=UTF-8");        PrintWriter out = response.getWriter();        //显示所有的商品，提供查看详细内容的链接        out.write("<h1>本站有以下好书：</h1>");        Map<String, Book> books = BookDB.findAllBooks();        for(Map.Entry<String, Book> me:books.entrySet()){            out.write(me.getValue().getName()+"&nbsp;&nbsp;<a href='"+request.getContextPath()+"/servlet/ShowDetailsServlet?id="+me.getKey()+"' target='_blank'>查看详细</a><br/>");        }        //显示最近的浏览记录：3条  bookHistory=2-1-3        out.write("<hr/>您最近的浏览记录如下：<br/>");        Cookie cs[] = request.getCookies();        for(int i=0;cs!=null&&i<cs.length;i++){            if("bookHistory".equals(cs[i].getName())){                String value = cs[i].getValue();// 2-1-3                String ids[] = value.split("\\-");                for(String id:ids){                    out.write(BookDB.findById(id).getName()+"<br/>");                }                break;            }        }    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

ShowDetailsServlet.java文件：

package com.itheima.cookie.app3;import java.io.IOException;import java.io.PrintWriter;import java.util.ArrayList;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;//显示商品的详细内容//组织数据，向客户端写cookiepublic class ShowDetailsServlet extends HttpServlet {    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        response.setContentType("text/html;charset=UTF-8");        PrintWriter out = response.getWriter();        //显示商品的详细内容        String id = request.getParameter("id");        Book book = BookDB.findById(id);        out.write(book.toString());        //组织数据，向客户端写cookie 3条  bookHistory=2-1-3        String bookId = makeId(id,request);        Cookie c = new Cookie("bookHistory", bookId);        c.setPath(request.getContextPath());        response.addCookie(c);    }    //组织数据    /*    客户端带来的cookie                            当前访问的书的id           应该写回去的新id    cookie为null                             1               bookHistory=1    cookie不为null，但没有bookHistory         1               bookHistory=1    bookHistory=1                           2               bookHistory=2-1    bookHistory=1-2                         3               bookHistory=3-1-2    bookHistory=1-2                         2               bookHistory=2-1    bookHistory=1-2-3                       4               bookHistory=4-1-2    bookHistory=1-2-3                       2               bookHistory=2-1-3     */    private String makeId(String id, HttpServletRequest request) {//      cookie为null                             1               bookHistory=1        Cookie cs[] = request.getCookies();        if(cs==null){            return id;        }//      cookie不为null，但没有bookHistory         1               bookHistory=1        Cookie bookHistoryCookie = null;        for(Cookie c:cs){            if("bookHistory".equals(c.getName())){                bookHistoryCookie = c;                break;            }        }        if(bookHistoryCookie==null){            return id;        }//      bookHistory=1                           2               bookHistory=2-1//      bookHistory=1-2                         3               bookHistory=3-1-2//      bookHistory=1-2                         2               bookHistory=2-1        String value = bookHistoryCookie.getValue();        String ids[] = value.split("\\-");        LinkedList<String> list = new LinkedList<String>(Arrays.asList(ids));        if(list.size()<3){            if(list.contains(id)){                list.remove(id);            }        }else{//      bookHistory=1-2-3                       4               bookHistory=4-1-2//      bookHistory=1-2-3                       2               bookHistory=2-1-3            if(list.contains(id)){                list.remove(id);            }else{                list.removeLast();            }        }        list.addFirst(id);        StringBuffer sb = new StringBuffer();        for(int i=0;i<list.size();i++){            if(i>0){                sb.append("-");            }            sb.append(list.get(i));        }        return sb.toString();    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

Book.java文件：

package com.itheima.cookie.app3;public class Book {    private String id;    private String name;    private String price;    private String author;    private String 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 getAuthor() {        return author;    }    public void setAuthor(String author) {        this.author = author;    }    public String getDescription() {        return description;    }    public void setDescription(String description) {        this.description = description;    }    @Override    public String toString() {        return "Book [id=" + id + ", name=" + name + ", price=" + price                + ", author=" + author + ", description=" + description + "]";    }    public Book(String id, String name, String price, String author,            String description) {        super();        this.id = id;        this.name = name;        this.price = price;        this.author = author;        this.description = description;    }    public Book(){}}

BookDB.java文件：

package com.itheima.cookie.app3;import java.util.HashMap;import java.util.Map;//模拟数据public class BookDB {    //key:书的id  value：id对应的书    private static Map<String,Book> books = new HashMap<String,Book>();    static{        books.put("1", new Book("1", "葵花宝典", "10", "牛骞", "欲练此功，必须很牛"));        books.put("2", new Book("2", "欲女心经", "2", "薛振宇", "欲练此功，必须清纯"));        books.put("3", new Book("3", "金瓶梅", "20", "刘春龙", "爱情经典"));        books.put("4", new Book("4", "辟邪剑法", "10", "王雷", "欲练此功，必须很牛"));        books.put("5", new Book("5", "JavaWeb开发", "100", "王昭珽", "经典著作"));    }    public static Map<String,Book> findAllBooks(){        return books;    }    public static Book findById(String bookId){        return books.get(bookId);    }}

运行：http://localhost:8080/Cookie/servlet/ShowAllBooksServlet
结果：