JavaWeb -- Cookie应用实例 -- 购物历史记录

1.

页面一：主页面                                         页面二： 详细显示页面

 

Demo2 负责页面一， 显示商品清单和历史记录

Demo3负责页面二，显示商品详细内容 和  写入相应的Cookie

SevletDemo2 代码：

package com.kevin;

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

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

/**
 * Servlet implementation class Demo2
 */
@WebServlet("/Demo2")
public class Demo2 extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public Demo2() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		
		//1.display all commodity
		out.write("本网站所有商品如下：<br/>");
		Map<String, Book> map = Db.getAll();
		for(Map.Entry<String, Book> entry : map.entrySet())
		{
			Book book = entry.getValue();
			out.print("<a href='/WebTest3/Demo3?id="+ book.getId() 
					+"' target='_blank'>"+ book.getName() +"</a>" + "<br/>");
		}
				
		//2.display book history
		out.print("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("\,");
				for(String id : ids)
				{
					//System.out.println("id=" + id);
					Book book = (Book) Db.getAll().get(id);
					out.print(book.getName() + "<br/>");
				}
			}
		}
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}

}

class Db
{
	private static Map<String, Book> map = new LinkedHashMap<String, Book>();
	static
	{
		map.put("1", new Book("1", "JavaWeb", "zhangsan", "a good book"));
		map.put("2", new Book("2", "Jdbc", "lisi", "a good book"));
		map.put("3", new Book("3", "Spring", "wangwu", "a good book"));
		map.put("4", new Book("4", "Struts", "zhaoliu", "a good book"));
		map.put("5", new Book("5", "Android", "zhangfa", "a good book"));
	}
	
	public static Map getAll()
	{
		return map;
	}
	
}

class Book
{
	private String id;
	private String name;
	private String author;
	private String description;
			
	public Book() {
		super();
		// TODO Auto-generated constructor stub
	}
	public Book(String id, String name, String author, String description) {
		super();
		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;
	}	
}

ServletDemo3代码：

package com.kevin;

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

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

/**
 * Servlet implementation class Demo3
 */
@WebServlet("/Demo3")
public class Demo3 extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public Demo3() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		response.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		//out.print("Demo3");
		
		//1. display detail info by id	
		String id = request.getParameter("id");	
		Book book = (Book) Db.getAll().get(id);
		if(book !=null)
		{
			out.write(book.getId() + "<br/>");
			out.write(book.getAuthor() + "<br/>");
			out.write(book.getName() + "<br/>");
			out.write(book.getDescription() + "<br/>");
		}
		
		//2. write cookie
		String cookieValue = buildCookie(id, request);
		Cookie cookie = new Cookie("bookHistory", cookieValue);
		cookie.setMaxAge(30*24*3600);
		cookie.setPath("/WebTest3");		
		
		response.addCookie(cookie);
	}

	private String buildCookie(String id, HttpServletRequest request) {
		//max num = 3
		//bookHistory=null    look:1     return:1 
		//bookHistory=2,3,4   look:4     return:4,2,3
		//bookHistory=2,3,4   look:1     return:1,2,5
		//bookHistory=2,3     look:4     return:2,3,4 
		
		String bookHistory = null;
		Cookie[] cookies = request.getCookies();
		for(int i=0; cookies!=null && i<cookies.length; i++)
		{			
			if( cookies[i].getName().equals("bookHistory") )
			{
				System.out.println("hava bookHistory");
				bookHistory = cookies[i].getValue();
			}
		}
		
		System.out.println("bookHistory=" + bookHistory);
		
		if(bookHistory==null)
			return id;
		
		LinkedList<String> list = new LinkedList<String>(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 id2 : list)
		{
			sb.append(id2 + ",");
		}
		
		return sb.deleteCharAt(sb.length()-1).toString();
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}

}