cookie记录浏览记录

cookie记录浏览记录

HashMap也是我们使用非常多的Collection，它是基于哈希表的 Map 接口的实现，以key-value的形式存在。在HashMap中，key-value总是会当做一个整体来处理，系统会根据hash算法来来计算key-value的存储位置，我们总是可以通过key快速地存、取value。下面就来分析HashMap的存取。

javabean.java

 定义Book类的五个属性

package Book.bean;

public class Book {

    private String id;
    
    private String bookName;
    
    private String author;
    
    private float price;
    
    private String description;
    
    
//带参数的构造函数
    public Book(String id, String bookName, String author, float price,
            String description) {
        this.id = id;
        this.bookName = bookName;
        this.author = author;
        this.price = price;
        this.description = description;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getBookName() {
        return bookName;
    }

    public void setBookName(String bookName) {
        this.bookName = bookName;
    }

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public float getPrice() {
        return price;
    }

    public void setPrice(float price) {
        this.price = price;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    @Override
    public String toString() {
        return "Book [id=" + id + ", bookName=" + bookName + ", author="
                + author + ", price=" + price + ", description=" + description
                + "]";
    }
}

BookUtils.java  

存取书的内容，利用hashMap来存取数据

package Book.utils;

import java.util.HashMap;
import java.util.Map;

import Book.bean.Book;

//书放到数据库中的实现类
public class BookUtils {

    //为了方便，创建一个静态的Map
    private static Map<String,Book> map = new HashMap<String,Book>();
    //静态块
    static{
        map.put("1", new Book("1","降龙十1掌","金庸1",1,"武功绝学降龙十1掌"));
        map.put("2", new Book("1","降龙十2掌","金庸2",2,"武功绝学降龙十2掌"));
        map.put("3", new Book("1","降龙十3掌","金庸3",3,"武功绝学降龙十3掌"));
        map.put("4", new Book("1","降龙十4掌","金庸4",4,"武功绝学降龙十4掌"));
        map.put("5", new Book("1","降龙十5掌","金庸5",5,"武功绝学降龙十5掌"));
        map.put("6", new Book("1","降龙十6掌","金庸6",6,"武功绝学降龙十6掌"));
        map.put("7", new Book("1","降龙十7掌","金庸7",7,"武功绝学降龙十7掌"));
        map.put("8", new Book("1","降龙十8掌","金庸8",8,"武功绝学降龙十8掌"));
        map.put("9", new Book("1","降龙十9掌","金庸9",9,"武功绝学降龙十9掌"));
        map.put("10", new Book("1","降龙十掌","金庸10",10,"武功绝学降龙十掌"));
        map.put("11", new Book("1","降龙十1掌","金庸11",11,"武功绝学降龙十1掌"));
    }
    //拿取书
    public static Map<String,Book> getAllBook(){
        return map;
    }
    //获取一本书
    public static Book getBookById(String id){
        return map.get(id);
    }
}

showAllBook.java

读取并显示书籍信息

package Book.servlet;

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;

import Book.bean.Book;
import Book.utils.BookUtils;

public class showAllBook extends HttpServlet {

    /**
     * 1.显示所有的书
     * 2.显示浏览的历史记录
     * The doGet method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to get.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        
        out.write("书架：<br>");
        //1.显示所有的书
        Map<String,Book> map = BookUtils.getAllBook();
        //遍历集合 foreach
        for (Map.Entry<String, Book> entry : map.entrySet()) {
            //拿到每一本书的id
            String id = entry.getKey();
            //拿到每一本书
            Book book = entry.getValue();
            //output book name
            //客户端跳转
            out.write(book.getBookName() + "&nbsp;<a href='" + request.getContextPath() + "/servlet/ShowDetail?id=" + id + " '>显示详细信息</a><br>");
            
        }
        
        out.write("<br><br><br>");
        //显示浏览的历史记录:cookie的名字定义为history : 值的形式：1-2-3
        //拿到cookie，
        Cookie[] cs = request.getCookies();
        //for
        for (int i = 0; cs != null && i < cs.length; i++) {
            Cookie c = cs[i];
            if("history".equals(c.getName())){
                //show
                out.write("你的浏览记录：<br>");
                //got cookie
                String value = c.getValue();
                //根据形式来拆分成数组
                String [] ids = value.split("-");
                //show the book
                for (int j = 0; j < ids.length; j++) {
                    Book b = BookUtils.getBookById(ids[j]);
                    out.write(b.getBookName() + "<br>");
                }
            }
        }
        
    }

    /**
     * The doPost method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to post.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        doGet(request, response);
    }

}

ShowDetail.java 

1.显示书的详细信息： 获取传递过来的 id ，通过BookUtils来获取书的全部信息

2.显示浏览记录 ： 获取传递过来的cookie，分析处理cookie

package Book.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.LinkedList;

import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import Book.bean.Book;
import Book.utils.BookUtils;

/**
 * 1.显示书的详细信息
 * 2.发送历史浏览记录
 * @author kj
 *
 */
public class ShowDetail extends HttpServlet {

    /**
     * The doGet method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to get.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        //1.拿到传递的数据
        String id = request.getParameter("id");
        //根据id查询书
        Book book = BookUtils.getBookById(id);
        //显示书的信息
        out.write(book + "&nbsp;&nbsp;<a href='" + request.getContextPath() + "/servlet/showAllBook'>返回主页继续浏览</a><br>");
        
        //2.发送cookie
        //获取历史记录字符串
        String history = getHistory(request,id);
        //创建cookie
        Cookie c = new Cookie("history",history);
        c.setMaxAge(Integer.MAX_VALUE);
        //设置Cookie存放路径
        c.setPath(request.getContextPath());
        response.addCookie(c);
    }

    /**
     * 获取要发往客户端的历史记录的字符串
     * @return
     */
    private String getHistory(HttpServletRequest request, String id) {
        // 获取字符串的情况
        /**
         * 历史记录的的cookie被获取                                            点击的书                                                 结果
         * 1.        null                      n                   n
         * 2.         1                           1                   1
         * 3.         1                        2                   2-1
         * 4          1-2                      1                   1-2
         * 5.         1-2                      2                    2-1
         * 6.         1-2                      3                    3-1-2
         * 7.          1-2-3                    1                   1-2-3
         * 8.         1-2-3                    2                   2-1-3
         * 9.         1-2-3                    3                   3-1-2
         * 10         1-2-3                    4                   4-1-2
         */
        //设定一个cookie为空，用来存放获取到的原来的cookie
        Cookie history = null;
        //拿到所有的cookie
        Cookie[] cs = request.getCookies();
        //循环判断所有的cookie
        for (int i = 0; cs!=null && i < cs.length; i++) {
            if(cs[i].getName().equals("history")){
                history = cs[i];
                break;
            }
        }
        //情况1，history为空，没有，就把id添加进去
        if(history == null)
            return id;
        //如果不为空
        String value = history.getValue();
        System.out.println("----value的长度-----" + value.length()+"***value的值***"+ value);
        if(value.length() == 1 ){
            //2,3的情况
            if(value.equals(id)){
                //第一种情况
                return id;
            }else{
                return id + "-" + value;
            }
            
        }
        //剩下的就是大于1的情况了，说明有两个或两个以上的，这就需要拆封成单个字符串了
        String[] ids = value.split("-");
        ////Arrays.asList 返回一个受指定数组支持的固定大小的列表,也可以用for循环
        LinkedList<String> list = new LinkedList<String>(Arrays.asList(ids));
        //返回此列表中首次出现的指定元素的索引，如果此列表 中不包含该元素，则返回 -1
        int index = list.indexOf(id);
        //4,5,6的情况
        
//        value的值包括 “a” “-” “b” 所以是3
        if(value.length() == 3){
            System.out.println("######进入 value=3 的情况######");
            if(index == -1){
                //说明没有点击过
                list.addFirst(id);
            }else{
                //说明是点击过的书
                list.remove(index);
                list.add(id);
            }
        }
        //7,8,9,10的情况，都是三个数
        if(value.length() > 3){
            System.out.println("@@@@@@@进入 value>3 的情况@@@@@@@");
            if(index == -1 ){
                list.removeLast();
                list.addFirst(id);
            }else{
                list.remove(index);
                list.addFirst(id);
            }
        }
        
        //处理完成后需要将数据输出成字符串的形式
        StringBuffer sb = new StringBuffer(list.get(0));
        for (int j = 1; j < list.size(); j++) {
            sb.append("-" + list.get(j));
        }
        
        return sb.toString();
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        doGet(request, response);
    }
}