Cookie小案例------记住浏览过的商品记录

我们知道，这个功能在电商项目中非经常见。这里处理请求和页面显示都是由servlet实现，主要是为了体现cookie的作用，

实现功能例如以下：

1，点击购买的商品后，显示到还有一页面

2。记住用户浏览过的商品，并在页面时中显示

3，当浏览过的数量超过最大值限度时，最以下一个商品被挤下去

4，当浏览过的商品本身就在浏览记录中，显示列表将其从中间移到最上面

显示一打开站点的样子和显示用户的浏览记录：

package cn.itcast.cookie;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.HashMap;

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;

//站点首页

public class CookieDemo2 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		response.setContentType("text/html;charset=UTF-8");

		response.setCharacterEncoding("UTF-8");

		PrintWriter  out = response.getWriter();

		//1.显示站点全部商品

		out.print("本站点有例如以下书籍：<br/>");

		Map<String,Book> map = DB.getMap();

		for(Map.Entry<String, Book> entry : map.entrySet()){

			Book book = entry.getValue();

			out.print("<a href='/day07/servlet/CookieDemo3?

id="+book.getId()+"' target='_blank'>"+book.getName()+"</a><br/>");

		}

		out.print("您以前看过例如以下商品：<br/>");

		//2.显示用户以前浏览过的商品    //   bookHistory

		Cookie cookie = null;

		Cookie cookies[] = request.getCookies();

		for(int i=0;cookies!=null && i<cookies.length;i++){

			if(cookies[i].getName().equals("bookHistory")){

				cookie = cookies[i];

			}

		}

		if(cookie!=null){

			//找到了bookHistory这个cookie

			String bookHistory = cookie.getValue();   //4_6_1

			String ids[] = bookHistory.split("\\_");

			for(String id: ids){

				Book book = (Book) DB.getMap().get(id);

				out.print(book.getName() + "<br/>");

			}

		}

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		doGet(request, response);

	}

}

class DB{

	private static Map<String,Book> map = new HashMap();

	static{

		map.put("1", new Book("1","javaweb开发","老张"));

		map.put("2", new Book("2","jdbc开发","老黎"));

		map.put("3", new Book("3","struts2开发","老张"));

		map.put("4", new Book("4","spring开发","老黎"));

		map.put("5", new Book("5","hibernate开发","老张"));

	}

	public static Map getMap(){

		return map;

	}

}

class Book{

	private String id;

	private String name;

	private String author;

	public Book() {

		super();

		// TODO Auto-generated constructor stub

	}

	public Book(String id, String name, String author) {

		super();

		this.id = id;

		this.name = name;

		this.author = author;

	}

	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;

	}

}

用于显示商品的具体信息：

package cn.itcast.cookie;

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;

//显示商品具体信息

public class CookieDemo3 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		response.setContentType("text/html;charset=UTF-8");

		response.setCharacterEncoding("UTF-8");

		PrintWriter  out = response.getWriter();

		//1.依据用户带过来的id值，显示对应商品的信息

		out.print("您想看的书的具体信息为：<br/>");

		String id = request.getParameter("id");

		Book book = (Book) DB.getMap().get(id);

		out.print(book.getId() + "<br/>");

		out.print(book.getName() + "<br/>");

		out.print(book.getAuthor() + "<br/>");

		//2.以cookie的形式回写该商品的id号给浏览器

		String bookHistory = makeCookie(book.getId(),request);

		Cookie cookie = new Cookie("bookHistory",bookHistory);

		cookie.setMaxAge(10000);

		response.addCookie(cookie);

	}

	//依据用户原来看过的书，以及如今看的书的id，构建新的cookie值

	private String makeCookie(String id, HttpServletRequest request) {

		//bookHistory=null    3     bookHistory=3

		//bookHistory=2_1_5   3     bookHistory=3_2_1

		//bookHistory=2       3     bookHistory=3_2

		//bookHistory=2_3     3     bookHistory=3_2

		//1.得到用户以前看过的书

		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(bookHistory==null){

			bookHistory = id;

			return bookHistory;

		}

		//bookHistory=1_2_5    代表用户以前看一些书。接着程序要得到用户以前看过什么书

		String ids[] = bookHistory.split("_");

		//为了检測数组中是否包括当前id，我们应该把数据转成集合，而且还要转成链表结构的集合

		LinkedList<String> idList = new LinkedList(Arrays.asList(ids));

		/*if(idList.contains(id)){

			//bookHistory=2_3     3     bookHistory=3_2

			idList.remove(id);

			idList.addFirst(id);

		}else{

			//bookHistory=2_1_5   3     bookHistory=3_2_1

			if(idList.size()>=3){

				idList.removeLast();

				idList.addFirst(id);

			}else{

				//bookHistory=2       3     bookHistory=3_2

				idList.addFirst(id);

			}

		}*/

		if(idList.contains(id)){

			idList.remove(id);

		}else{

			if(idList.size()>=3){

				idList.removeLast();

			}

		}

		idList.addFirst(id);

		StringBuffer sb = new StringBuffer();

		for(String lid: idList){   //1_2_3_

			sb.append(lid + "_");

		}

		return sb.deleteCharAt(sb.length()-1).toString();

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		doGet(request, response);

	}

}

执行效果：