Cookie应用--显示看过的商品

package cn.itcast;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;

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 CookieDemo 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 {
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out=response.getWriter();
        //输出所有商品
        out.write("本站所有商品<br/>");
        Map<String,Book> map=Db.getAll();
        for(Entry<String, Book> entry: map.entrySet()){
            Book book=entry.getValue();
            out.print("<a href='/day01/servlet/CookieDemo2?id="+book.getId()+"' target='_blank'>"+book.getName()+"</a></br>");
            
        }
        //显示用户看过的商品
        out.print("<br/>看过的商品<br/>");
        Cookie cookies[]=request.getCookies();
        for(int i=0;cookies!=null&&i<cookies.length;i++){
            if(cookies[i].getName().equals("bookHistory")){
                String ids[]=cookies[i].getValue().split("\,");
                for(String id:ids){
                    Book book=(Book) Db.getAll().get(id);
                    
                    out.print(book.getName()+"<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);
    }

}
//模拟 数据库
class Db{
    private static Map<String, Book> map =new LinkedHashMap();
    static{
        map.put("1", new Book("1","java开发1","zsan1","一本好书1"));
        map.put("2", new Book("2","java开发2","zsan2","一本好书2"));
        map.put("3", new Book("3","java开发3","zsan3","一本好书3"));
        map.put("4", new Book("4","java开发4","zsan4","一本好书4"));
        
    }
    public static Map getAll(){
        return map;}
    
}
class Book{
    private String id;
    private String name;
    private String author;
    private String desc;
    
    public Book() {
        super();
        // TODO Auto-generated constructor stub
    }
    public Book(String id, String name, String author, String desc) {
        super();
        this.id = id;
        this.name = name;
        this.author = author;
        this.desc = desc;
    }
    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 getDesc() {
        return desc;
    }
    public void setDesc(String desc) {
        this.desc = desc;
    }
    
}

package cn.itcast;

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 CookieDemo2 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 {
        //根据用户带过来的id显示相应的详细信息
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out=response.getWriter();
        out.write("本站所有商品<br/>");
        String id=request.getParameter("id");
        Book book=(Book) Db.getAll().get(id);
        out.write(book.getDesc());
        //2.构建cookie，回写给浏览器
        String cookieValue=bulidCookie(id,request);
        Cookie cookie=new Cookie("bookHistory",cookieValue);
        cookie.setMaxAge(30*24);
        cookie.setPath("/day01");
        response.addCookie(cookie);
        
        
    }

    private String bulidCookie(String id, HttpServletRequest request) {
        // TODO Auto-generated method stub
        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();
            }
            
        }
        if(cookies==null)
        {
            return id;
        }
        LinkedList<String> list= new LinkedList(Arrays.asList(bookHistory.split("\,")));
        if(list.contains(id)){
            list.remove(id);
            list.addFirst(id);
            
        }
        else
        {
            if(list.size()>=3){
                list.removeLast();
                list.addFirst(id);
            }
            else{
                list.addFirst(id);
            }
        }
        StringBuffer sb=new StringBuffer();
        for(String bid: list){
            sb.append(bid+",");
            
        }
        return sb.deleteCharAt(sb.length()-1).toString();

        
    }

    /**
     * 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);
    }

}