展示商品历史浏览记录

废话不多说，直接上代码

package cn.itcast.cookie;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
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;
//清除cookie

public class CookieDemo3 extends HttpServlet {

     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("本站有如下商品:<br/>");
          Map<String,Book>map=Db.getAll();
          for(Map.Entry<String, Book> entry:map.entrySet()){
               Book book=entry.getValue();
               out.print("<a target=\"_blank\" href='/day07/servlet/cookieDemo4?id="+book.getId()+"'>"+book.getName()+"</a><br/>");
               
          }
          //显示用户看过的商品
          out.print("<br/>你曾经看过的商品<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("\\,");//2,3,1
                    for(String id:ids){
                         Book book=(Book) Db.getAll().get(id);
                         out.print("<a target=\"_blank\" href='/day07/servlet/cookieDemo4?id="+book.getId()+"'>"+book.getName()+"</a><br/>");
                    }
               }
          }
     }
}

class Db{
     private static Map<String,Book> map=new LinkedHashMap<String,Book>();
     static {
          map.put("1", new Book("1","JavaWeb开发","老k","一本好书"));
          map.put("2", new Book("2","jdbc开发","老张","一本好书"));
          map.put("3", new Book("3","spring开发","老li","一本好书"));
          map.put("4", new Book("4","struts开发","老张","一本好书"));
          map.put("5", new Book("5","android开发","老bi","一本好书"));
     }
     public static Map getAll(){
          return map;
     }
     
}

class Book{
     private String id;
     private String name;
     private String author;
     private String description;
     
     public Book() {
          super();
    }
     public Book(String id, String name, String author, String description) {
          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;
     }     
}

package cn.itcast.cookie;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Date;
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;
//显示详细信息的servlet

public class CookieDemo4 extends HttpServlet {

     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();
          String id=request.getParameter("id");
          Book book=(Book)Db.getAll().get(id);
          out.write(book.getId()+"<br/>");
          out.write(book.getName()+"<br/>");     
          out.write(book.getAuthor()+"<br/>");
          out.write(book.getDescription()+"<br/>");
          //2.构建cookie，回写给浏览器；
          String cookieValue=buildCookie(id,request);
          Cookie cookie=new Cookie("bookHistory",cookieValue);
          cookie.setMaxAge(1*30*24*3600);//1 个月
          cookie.setPath("/day07");
          response.addCookie(cookie);          
     }

     private String buildCookie(String id, HttpServletRequest request) {
          //bookHistory =null   1    1
          //bookHistory=2,5,1   1    1,2,5
          //bookHistory=2,5,4   1    1,2,5
          //bookHistroy=2,5     1    1,2,5   // 假如列表最多3个
          String bookHistroy=null;
          Cookie cookies[]=request.getCookies();
          for(int i=0;cookies!=null && i<cookies.length;i++){
               if(cookies[i].getName().equals("bookHistory")){
                    bookHistroy=cookies[i].getValue();                    
               }
          }
          if(bookHistroy==null)
               return id;
          //if(bookHistroy.contains(id))不能这样  21,23 也包括1
          List<String> list=Arrays.asList(bookHistroy.split("\\,"));
          LinkedList <String>linkedlist=new LinkedList<String>(list);
          if(list.contains(id)){
               linkedlist.remove(id);
               linkedlist.addFirst(id);
          }else{
               if(list.size()>=3){
                    linkedlist.removeLast();
                    linkedlist.addFirst(id);
               }else
                    linkedlist.addFirst(id);
          }
          StringBuffer sb=new StringBuffer();
          for(String bid : linkedlist){
               sb.append(bid+",");
          }
          return sb.deleteCharAt(sb.length()-1).toString();          
     }

}