JavaEE Cookie HttpSession 学习笔记

1. 会话管理概述

1.1 什么是会话

好比一次通话。打开浏览器，点击多次链接（发出多次请求和收到多次的响应），关闭浏览器，这个过程就是一次会话。

　 有功能 可以  文件　新建会话  

　　

1.2 解决的问题是什么

共享多次请求中产生的数据。比如购物车。

 

1.3 Application Session Cookie 生命周期 简要区别

方法	信息量大小	保存时间	应用范围	保存位置
Application	任意大小	整个应用程序的生命期	所有用户	服务器端
Session	小量,简单的数据	用户活动时间+一段延迟时间(一般为20分钟)	单个用户	服务器端
Cookie	小量,简单的数据	可以根据需要设定	单个用户	客户端

2. 客户端技术：Cookie

2.1 HTTP协议的消息头

请求消息头：Cookie 客户端向服务器端传递信息

响应消息头：Set-Cookie 服务器端向客户端传递信息

2.2 Cookie详解

l  属性：

name：Cookie的名称，必要的属性

value：Cookie的取值（不能为中文），必要的属性

-------------------以下为可选属性

path：Cookie的路径

　　默认值就是写cookie的那个资源的访问路径

　　比如：http://localhost:8080/day09_00_cookie/servlet/CookieDemo1 path就是/day09_00_cookie/servlet/

　　注意：

 　　  如果一个存在浏览器缓存中的cookie的路径是/day09/servlet/

   　　当访问http://localhost:8080/day09/CookiePathDemo1时，

  　　 浏览器根本不带Cookie给服务器。浏览器比对的是cookie的路径和当前访问的资源的路径。

 　　  浏览器满足一下条件就会带cookie给服务器：

          　　当前访问的地址的路径.startWith(已存cookie的路径)。

            即：如果一个Cookie的路径设置为了当前应用，说明访问该网站的任何资源时浏览器都带该cookie给服务器。（开发中经常做的）

maxAge：Cookie的最大生存时间。默认是在浏览器的内存中。

domain：Cookie的域名（网站）。默认就是写cookie的那个资源所属的网站。

　　　　 http://localhost:8080/day09_00_cookie/servlet/CookieDemo1域名就是localhost

version：版本号

comment:注释

 

u  把Cookie写给客户端：

HttpServletResponse.addCookie(Cookie c):实际上就是向客户端发送了一个响应消息头。

注意：客户端只能保存一个网站最多20个Cookie数据，总共最多300个。每个Cookie的大小不能超过4kb。

l  服务器端获取客户端带来的Cookie：

Cookie [] HttpServletRequest.getCookies();

注意：domain+path+name唯一确定一个Cookie。

 

2.3 3个案例

2.3.1 显示用户最近的访问时间

public class CookieDemo1 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		out.write("您上次访问的时间是：<a href='"+request.getContextPath()+"/servlet/ClearTimeServlet'>清除时间</a>");
		
		//获取指定名称的cookie：lastAccessTime=毫秒值
		Cookie cs[] = request.getCookies();
		for(int i=0;cs!=null&&i<cs.length;i++){
			if("lastAccessTime".equals(cs[i].getName())){
				//找到了
				long time = Long.parseLong(cs[i].getValue());
				out.write(new Date(time).toLocaleString());
			}
		}
		
		
		//把当前的时间写回去
		Cookie c = new Cookie("lastAccessTime", System.currentTimeMillis()+"");
		c.setMaxAge(Integer.MAX_VALUE);//单位是秒
		response.addCookie(c);
	}

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

 

//清除指定的cookie
public class ClearTimeServlet extends HttpServlet {
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//如何唯一定位要删除的cookie：domain+path+name
		Cookie c = new Cookie("lastAccessTime", "");
		c.setMaxAge(0);
		response.addCookie(c);
	}

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


}

 

演示Cookie的path

public class CookiePathDemo1 extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //path：/day09/servlet/
        Cookie c = new Cookie("demoCookie", "aaa");
        c.setPath(request.getContextPath());// 把路径改为 /day09
        c.setMaxAge(Integer.MAX_VALUE);
//        c.setDomain("itheima.com");//写了白写
        response.addCookie(c);
    }

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

}

public class CookiePathDemo2 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		Cookie cs[] = request.getCookies();
		for(int i=0;cs!=null&&i<cs.length;i++){
			if("demoCookie".equals(cs[i].getName())){
				//找到了
				response.getWriter().write(cs[i].getValue());
			}
		}
	}

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

}

 

 

2.3.2 记住登录的用户名

public class LoginUIServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		
		String username = "";
		String checked = "";
		//得到指定的cookie
		Cookie cs[] = request.getCookies();
		for(int i=0;cs!=null&&i<cs.length;i++){
			if("loginInfo".equals(cs[i].getName())){
				username = cs[i].getValue();
				checked="checked='checked'";
				break;
			}
		}
		
		
		out.write("<form action='"+request.getContextPath()+"/servlet/LoginServlet' method='post'>");
		out.write("用户名：<input type='text' name='username' value='"+username+"'/><br/>");
		out.write("密码：<input type='password' name='password' value=''/><br/>");
		out.write("记住用户名：<input type='checkbox' name='remember' "+checked+"/><br/>");
		out.write("<input type='submit' value='登录'/>");
		out.write("</form>");
		
	}

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

}

 

public class LoginServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		
		//验证用户名和密码是否正确：此处输什么都正确
		String username = request.getParameter("username");
		String password = request.getParameter("password");
		String remember = request.getParameter("remember");//没有选中就是null
		
		Cookie c = new Cookie("loginInfo", username);
		c.setPath(request.getContextPath());
		if(remember==null){
			//没有选中：删cookie
			c.setMaxAge(0);
		}else{
			//用户记住用户名：存cookie
			c.setMaxAge(Integer.MAX_VALUE);
		}
		response.addCookie(c);
		out.write("登录成功");
		
	}

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

}

2.3.3 显示 最近浏览的产品 （图书）

 

//book类
public class Book {
	private String id;
	private String name;
	private String price;
	private String author;
	private String 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 getPrice() {
		return price;
	}
	public void setPrice(String price) {
		this.price = price;
	}
	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;
	}
	@Override
	public String toString() {
		return "Book [id=" + id + ", name=" + name + ", price=" + price
				+ ", author=" + author + ", description=" + description + "]";
	}
	public Book(String id, String name, String price, String author,
			String description) {
		super();
		this.id = id;
		this.name = name;
		this.price = price;
		this.author = author;
		this.description = description;
	}
	public Book(){}
}

 

//模拟数据
public class BookDB {
	//key:书的id  value：id对应的书
	private static Map<String,Book> books = new HashMap<String,Book>();
	static{
		books.put("1", new Book("1", "葵花宝典", "10", "nius", "欲练此功，必须很牛"));
		books.put("2", new Book("2", "欲女心经", "2", "xuez", "欲练此功，必须清纯"));
		books.put("3", new Book("3", "倾城之恋", "20", "liuc", "爱情经典"));
		books.put("4", new Book("4", "辟邪剑法", "10", "wangl", "欲练此功，必须很牛"));
		books.put("5", new Book("5", "JavaWeb开发", "100", "yif", "经典著作"));
	}
	public static Map<String,Book> findAllBooks(){
		return books;
	}
	public static Book findById(String bookId){
		return books.get(bookId);
	}
}

 

public class ShowAllBooksServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		//显示所有的商品，提供查看详细内容的链接
		out.write("<h1>本站有以下好书：</h1>");
		
		Map<String, Book> books = BookDB.findAllBooks();
		for(Map.Entry<String, Book> me:books.entrySet()){
			out.write(me.getValue().getName()+"  <a href='"+request.getContextPath()+"/servlet/ShowDetailsServlet?id="+me.getKey()+"' target='_blank'>查看详细</a><br/>");
		}
		
		//显示最近的浏览记录：3条  bookHistory=2-1-3
		out.write("<hr/>您最近的浏览记录如下：<br/>");
		Cookie cs[] = request.getCookies();
		for(int i=0;cs!=null&&i<cs.length;i++){
			if("bookHistory".equals(cs[i].getName())){
				String value = cs[i].getValue();// 2-1-3
				String ids[] = value.split("\\-");
				for(String id:ids){
					out.write(BookDB.findById(id).getName()+"<br/>");
				}
				
				break;
			}
		}
		
	}

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

}

 

//显示商品的详细内容
//组织数据，向客户端写cookie
public class ShowDetailsServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		//显示商品的详细内容
		
		String id = request.getParameter("id");
		Book book = BookDB.findById(id);
		out.write(book.toString());
		//组织数据，向客户端写cookie 3条  bookHistory=2-1-3
		String bookId = makeId(id,request);
		Cookie c = new Cookie("bookHistory", bookId);
		c.setPath(request.getContextPath());
		response.addCookie(c);
		
	}
	//组织数据
	
	/*
	客户端带来的cookie							当前访问的书的id			应该写回去的新id
	cookie为null								1				bookHistory=1
	cookie不为null，但没有bookHistory			1				bookHistory=1
	bookHistory=1							2				bookHistory=2-1
	bookHistory=1-2							3				bookHistory=3-1-2
	bookHistory=1-2							2				bookHistory=2-1
	bookHistory=1-2-3						4				bookHistory=4-1-2
	bookHistory=1-2-3						2				bookHistory=2-1-3
	 */
	
	private String makeId(String id, HttpServletRequest request) {
//		cookie为null								1				bookHistory=1
		Cookie cs[] = request.getCookies();
		if(cs==null){
			return id;
		}
//		cookie不为null，但没有bookHistory			1				bookHistory=1
		Cookie bookHistoryCookie = null;
		for(Cookie c:cs){
			if("bookHistory".equals(c.getName())){
				bookHistoryCookie = c;
				break;
			}
		}
		if(bookHistoryCookie==null){
			return id;
		}
//		bookHistory=1							2				bookHistory=2-1
//		bookHistory=1-2							3				bookHistory=3-1-2
//		bookHistory=1-2							2				bookHistory=2-1
		
		String value = bookHistoryCookie.getValue();
		String ids[] = value.split("\\-");
		LinkedList<String> list = new LinkedList<String>(Arrays.asList(ids));
		
		if(list.size()<3){
			if(list.contains(id)){
				list.remove(id);
			}
		}else{
		
//		bookHistory=1-2-3						4				bookHistory=4-1-2
//		bookHistory=1-2-3						2				bookHistory=2-1-3
			if(list.contains(id)){
				list.remove(id);
			}else{
				list.removeLast();
			}
		}
		list.addFirst(id);
		
		StringBuffer sb = new StringBuffer();
		for(int i=0;i<list.size();i++){
			if(i>0){
				sb.append("-");
			}
			sb.append(list.get(i));
		}
		
		return sb.toString();
	}

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

}

 

3. 服务器端技术：HttpSession

 

3.1 HttpSession是一个域对象及HttpSession的原理

　　void setAttribute(String name,Object value);

　　Object getAttribute(String name);

　　void removeAttribute(String name);

　　String getId()

　　HttpSession request.getSession();

//演示HttpSession的原理
public class SessionDemo1 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		
		String name = request.getParameter("name");
		if(name==null){
			out.write("请这样访问：http://192.168.33.172:8080/day09_01_HttpSession/servlet/SessionDemo1?name=abc");
			return;
		}
		//得到HttpSession的实例
		HttpSession session = request.getSession();
		//在创建HttpSession对象的同时，服务器给这个对象分配一个唯一的ID（GUID）
		System.out.println("SessionDemo1中HttpSession对象的id："+session.getId());
		session.setAttribute("p", name);
		
		out.write("放了。<a href='http://192.168.33.172:8080/day09_01_HttpSession/servlet/SessionDemo2'>去看看</a>");
	}

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

}

 

public class SessionDemo2 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		HttpSession session = request.getSession();
		System.out.println("SessionDemo2中HttpSession对象的id："+session.getId());
		String v = (String)session.getAttribute("p");
		response.getWriter().write(v);
	}

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

}

 

HttpSession request.getSession(boolean b):

b如果为true，和getSession()完全一样的

b为false，服务器只是查找，找不到不会创建新的，返回null。

HttpSession.invalidate();使HttpSession对象立即失效。

3.2 3个案例

3.2.1 使用Session完成简单的购物功能

使用上边的 book类 和 模拟 bookdb 数据

public class Book implements Serializable

//显示所有可购买的商品，提供购买链接
//提供一个查看购物车的链接
public class ShowAllBooksServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		request.getSession();   //为了使 url 重写 
		
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		//显示所有可购买的商品，提供购买链接
		out.write("<h1>本站有以下好书：</h1>");
		
		Map<String, Book> books = BookDB.findAllBooks();
		for(Map.Entry<String, Book> me:books.entrySet()){
			String url = request.getContextPath()+"/servlet/BuyServlet?id="+me.getKey();
			url = response.encodeURL(url);
			out.write(me.getValue().getName()+"  <a href='"+url+"'>购买</a><br/>");
		}
		//提供一个查看购物车的链接
		String url = request.getContextPath()+"/servlet/ShowCartServlet";
		url = response.encodeURL(url);
		out.write("<a href='"+url+"'>查看购物车</a>");
	}

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

}

 

//把书籍放入购物车
public class BuyServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		String id = request.getParameter("id");
		Book b = BookDB.findById(id);
		
		//放到HttpSession中》用List来存
		HttpSession session = request.getSession();
		List<Book> cart = (List<Book>) session.getAttribute("cart");
		if(cart==null){
			cart = new ArrayList<Book>();
			session.setAttribute("cart", cart);
		}
		//肯定有购物车
		cart.add(b);
		String url = request.getContextPath()+"/servlet/ShowAllBooksServlet";
		url = response.encodeURL(url);
		out.write(b.getName()+"已放入您的购物车<a href='"+url+"'>继续购物</a>");
		
		//为学习原理而做
//		Cookie c = new Cookie("JSESSIONID", session.getId());
//		c.setPath(request.getContextPath());
//		c.setMaxAge(Integer.MAX_VALUE);
//		response.addCookie(c);
	}

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

}

 

//显示购物车
public class ShowCartServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		
		HttpSession session = request.getSession();
		List<Book> cart = (List<Book>)session.getAttribute("cart");
		if(cart==null||cart.size()==0){
			out.write("您还没有购买任何商品");
			return;
		}
		
		out.write("<h1>你购买的商品如下</h1>");
		for(Book b:cart){
			out.write(b.getName()+"<br/>");
		}
	}

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

}

 

3.2.2 完成用户的登录

//user类
public class User {
	private String username;
	private String password;
	private String nickname;
	public User(){}
	
	public User(String username, String password, String nickname) {
		super();
		this.username = username;
		this.password = password;
		this.nickname = nickname;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	public String getNickname() {
		return nickname;
	}
	public void setNickname(String nickname) {
		this.nickname = nickname;
	}
	
}

 

public class UserDB {
	private static List<User> users = new ArrayList<User>();
	static{
		users.add(new User("wzt", "123", "动感超油"));
	}
	public static User login(String username,String password){
		for(User u:users){
			if(u.getUsername().equals(username)&&u.getPassword().equals(password)){
				return u;
			}
		}
		return null;
	}
}

 

//模拟主页
public class IndexServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		
		out.write("这是主页");
		
		HttpSession s = request.getSession();
		User user = (User)s.getAttribute("user");//获取登录标记
		if(user==null){
			//说明没有登录
			out.write("<a href='"+request.getContextPath()+"/servlet/LoginUIServlet'>登录</a>");
		}else{
			out.write("欢迎您："+user.getNickname()+"<a href='"+request.getContextPath()+"/servlet/LogoutServlet'>注销</a>");
		}
	}

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

}

 

//提供登录界面
public class LoginUIServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		out.write("<form action='"+request.getContextPath()+"/servlet/LoginServlet' method='post'>");
		out.write("用户名： <input type='text' name='username' /><br/>");
		out.write("密码： <input type='password' name='password' /><br/>");
		out.write("验证码： <input type='text' name='code' /><img src='"+request.getContextPath()+"/servlet/ImageServlet'/><br/>");
		out.write(" <input type='submit' value='登录' /><br/>");
		out.write("</form>");
		
	}

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

}

 

//登录检
public class LoginServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		String username = request.getParameter("username");
		String password = request.getParameter("password");
		User user = UserDB.login(username, password);
		if(user==null){
			out.write("错误的用户或密码,2秒后转向登录界面");
			response.setHeader("Refresh", "2;URL="+request.getContextPath()+"/servlet/LoginUIServlet");
			return;
		}
		HttpSession session = request.getSession();
		//验证码是否正确
		String code = request.getParameter("code");
		String scode = (String) session.getAttribute("code");
		if(!code.equals(scode)){
			out.write("错误的验证码,2秒后转向登录界面");
			response.setHeader("Refresh", "2;URL="+request.getContextPath()+"/servlet/LoginUIServlet");
			return;
		}
		
		//登录成功
		session.setAttribute("user", user);
		out.write("登录成功,2秒后转向主页");
		response.setHeader("Refresh", "2;URL="+request.getContextPath()+"/servlet/IndexServlet");
	}

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

}

 

//注销
public class LogoutServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		HttpSession session = request.getSession();
//		session.invalidate();//立即失效
		session.removeAttribute("user");
		
		out.write("注销成功,2秒后转向主页");
		response.setHeader("Refresh", "2;URL="+request.getContextPath()+"/servlet/IndexServlet");
	}

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

}

 

public class ImageServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		int width = 120;
		int height = 25;
		//创建一副内存图像
		BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
		//得到画笔
		Graphics g = image.getGraphics();
			//开始画
			//边线
			g.setColor(Color.BLUE);
			g.drawRect(0, 0, width, height);
			//填充背景色
			g.setColor(Color.YELLOW);
			g.fillRect(1, 1, width-2, height-2);
			//话干扰线
			g.setColor(Color.GRAY);
			
			Random r = new Random();
			for(int i=0;i<9;i++)
				g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width), r.nextInt(height));
			//验证码
			g.setColor(Color.RED);
			g.setFont(new Font("宋体", Font.ITALIC|Font.BOLD, 19));
//			String base = "\u7684\u4e00\u4e86\u662f\u6211\u4e0d\u5728\u4eba\u4eec\u6709\u6765\u4ed6\u8fd9\u4e0a\u7740\u4e2a\u5730\u5230\u5927\u91cc\u8bf4\u5c31\u53bb\u5b50\u5f97\u4e5f\u548c\u90a3\u8981\u4e0b\u770b\u5929\u65f6\u8fc7\u51fa\u5c0f\u4e48\u8d77\u4f60\u90fd\u628a\u597d\u8fd8\u591a\u6ca1\u4e3a\u53c8\u53ef\u5bb6\u5b66\u53ea\u4ee5\u4e3b\u4f1a\u6837\u5e74\u60f3\u751f\u540c\u8001\u4e2d\u5341\u4ece\u81ea\u9762\u524d\u5934\u9053\u5b83\u540e\u7136\u8d70\u5f88\u50cf\u89c1\u4e24\u7528\u5979\u56fd\u52a8\u8fdb\u6210\u56de\u4ec0\u8fb9\u4f5c\u5bf9\u5f00\u800c\u5df1\u4e9b\u73b0\u5c71\u6c11\u5019\u7ecf\u53d1\u5de5\u5411\u4e8b\u547d\u7ed9\u957f\u6c34\u51e0\u4e49\u4e09\u58f0\u4e8e\u9ad8\u624b\u77e5\u7406\u773c\u5fd7\u70b9\u5fc3\u6218\u4e8c\u95ee\u4f46\u8eab\u65b9\u5b9e\u5403\u505a\u53eb\u5f53\u4f4f\u542c\u9769\u6253\u5462\u771f\u5168\u624d\u56db\u5df2\u6240\u654c\u4e4b\u6700\u5149\u4ea7\u60c5\u8def\u5206\u603b\u6761\u767d\u8bdd\u4e1c\u5e2d\u6b21\u4eb2\u5982\u88ab\u82b1\u53e3\u653e\u513f\u5e38\u6c14\u4e94\u7b2c\u4f7f\u5199\u519b\u5427\u6587\u8fd0\u518d\u679c\u600e\u5b9a\u8bb8\u5feb\u660e\u884c\u56e0\u522b\u98de\u5916\u6811\u7269\u6d3b\u90e8\u95e8\u65e0\u5f80\u8239\u671b\u65b0\u5e26\u961f\u5148\u529b\u5b8c\u5374\u7ad9\u4ee3\u5458\u673a\u66f4\u4e5d\u60a8\u6bcf\u98ce\u7ea7\u8ddf\u7b11\u554a\u5b69\u4e07\u5c11\u76f4\u610f\u591c\u6bd4\u9636\u8fde\u8f66\u91cd\u4fbf\u6597\u9a6c\u54ea\u5316\u592a\u6307\u53d8\u793e\u4f3c\u58eb\u8005\u5e72\u77f3\u6ee1\u65e5\u51b3\u767e\u539f\u62ff\u7fa4\u7a76\u5404\u516d\u672c\u601d\u89e3\u7acb\u6cb3\u6751\u516b\u96be\u65e9\u8bba\u5417\u6839\u5171\u8ba9\u76f8\u7814\u4eca\u5176\u4e66\u5750\u63a5\u5e94\u5173\u4fe1\u89c9\u6b65\u53cd\u5904\u8bb0\u5c06\u5343\u627e\u4e89\u9886\u6216\u5e08\u7ed3\u5757\u8dd1\u8c01\u8349\u8d8a\u5b57\u52a0\u811a\u7d27\u7231\u7b49\u4e60\u9635\u6015\u6708\u9752\u534a\u706b\u6cd5\u9898\u5efa\u8d76\u4f4d\u5531\u6d77\u4e03\u5973\u4efb\u4ef6\u611f\u51c6\u5f20\u56e2\u5c4b\u79bb\u8272\u8138\u7247\u79d1\u5012\u775b\u5229\u4e16\u521a\u4e14\u7531\u9001\u5207\u661f\u5bfc\u665a\u8868\u591f\u6574\u8ba4\u54cd\u96ea\u6d41\u672a\u573a\u8be5\u5e76\u5e95\u6df1\u523b\u5e73\u4f1f\u5fd9\u63d0\u786e\u8fd1\u4eae\u8f7b\u8bb2\u519c\u53e4\u9ed1\u544a\u754c\u62c9\u540d\u5440\u571f\u6e05\u9633\u7167\u529e\u53f2\u6539\u5386\u8f6c\u753b\u9020\u5634\u6b64\u6cbb\u5317\u5fc5\u670d\u96e8\u7a7f\u5185\u8bc6\u9a8c\u4f20\u4e1a\u83dc\u722c\u7761\u5174\u5f62\u91cf\u54b1\u89c2\u82e6\u4f53\u4f17\u901a\u51b2\u5408\u7834\u53cb\u5ea6\u672f\u996d\u516c\u65c1\u623f\u6781\u5357\u67aa\u8bfb\u6c99\u5c81\u7ebf\u91ce\u575a\u7a7a\u6536\u7b97\u81f3\u653f\u57ce\u52b3\u843d\u94b1\u7279\u56f4\u5f1f\u80dc\u6559\u70ed\u5c55\u5305\u6b4c\u7c7b\u6e10\u5f3a\u6570\u4e61\u547c\u6027\u97f3\u7b54\u54e5\u9645\u65e7\u795e\u5ea7\u7ae0\u5e2e\u5566\u53d7\u7cfb\u4ee4\u8df3\u975e\u4f55\u725b\u53d6\u5165\u5cb8\u6562\u6389\u5ffd\u79cd\u88c5\u9876\u6025\u6797\u505c\u606f\u53e5\u533a\u8863\u822c\u62a5\u53f6\u538b\u6162\u53d4\u80cc\u7ec6";
			int x = 20;
			StringBuffer sb = new StringBuffer();
			for(int i=0;i<4;i++){
				String num = r.nextInt(10)+"";
				sb.append(num);
				g.drawString(num, x,20 );
//				g.drawString(base.charAt(r.nextInt(base.length()))+"", x, 20);
				x+=18;
			}
			
			request.getSession().setAttribute("code", sb.toString());
			
		//输出
		response.setHeader("Expires", "-1");
		response.setHeader("Cache-Control", "no-cache");
		response.setHeader("Pragma", "no-cache");
		ImageIO.write(image, "jpg", response.getOutputStream());
	}

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

}

 

3.2.3 防止表单的重复提交

//注册页面
public class RegistUIServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//产生一个唯一的ID（GUID就是UUID）
//		String token = UUID.randomUUID().toString();
		String token = new BigInteger(165, new Random()).toString(36).toUpperCase();//GUID
		
		request.getSession().setAttribute("token", token);
		
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		out.write("<form action='/day09_01_HttpSession/servlet/RegistServlet' method='post'>");
		out.write("姓名：<input name='name'/><br/>");
		out.write("<input type='hidden' name='token' value='"+token+"'/><br/>");
		out.write("<input type='submit' value='保存'/></form>");
	}

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

}

 

public class RegistServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("text/html;charset=UTF-8");
		PrintWriter out = response.getWriter();
		String name = request.getParameter("name");
//		try {
//			Thread.sleep(1000);
//		} catch (InterruptedException e) {
//			e.printStackTrace();
//		}//模拟网络慢
		
		String stoken = (String) request.getSession().getAttribute("token");
		String ftoken = request.getParameter("token");
		if(ftoken.equals(stoken)){
			System.out.println(name);
			request.getSession().removeAttribute("token");
		}else{
			out.write("请不要重复提交");
		}
		
		
	}

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

}

 

3.3 客户端禁用Cookie后的会话数据的保持

客户端永远不会向服务器端带任何cookie。

解决办法：

方式一：（乌龙）文字提示：请不要禁用您的Cookie

方式二：在访问的地址后面加上JSESSIONID=session的id。

http://localhost:8080/servlet/ServletDemo1   URL重写，必须对网站的所有地址都重写

http://localhost:8080/servlet/ServletDemo1;JSESSIONID=123

 

response.encodeUrl(String url);自动重写。 对购物车案例 修改了

 

3.4 HttpSession对象的状态

很多 银行的保护性就是将session 减短了。

public class Book implements Serializable 序列化

4 总结

一、会话概述
    1、如同一次电话通话。
    2、会话中要解决的问题：多次请求中的数据的保持问题。典型：购物车
二、Cookie
    1、属性：
        name value path maxAge domain version 等
    2、HttpServletResponse.addCookie(Cookie c)
    3、HttpServletRequest.getCookies()
    4、记住用户名和记住用户的浏览记录
三、HttpSession
    1、HttpSession是一个域对象
    2、HttpSession的原理（借助Cookie）
    3、HttpSession.getSession():先查（按照session对象的ID去查），没有再创建。
    4、案例：
        简单购物车
        用户登录和验证码验证
        防止表单的重复提交：从原理上明白
    5、客户端禁用了Cookie后的会话数据保持问题
        URL重写
    6、HttpSession对象的状态变化：钝化和激活。   向HttpSession中存放的对象的类，要实现java.io.Serializable接口
    7、浏览器何时会开启一次新的会话。