cookie和session

Posted 2022-09-20 lovemeng1314

会话

1 会话:用户打开浏览器，浏览页面，直到关闭浏览器的过程称为一次会话。
2 会话跟踪技术包括： Cookie（客户端技术）
3                 Session（服务器端技术）

cookie

  服务器负责：
　　　　　　　负责写cookie

　　　　　　　负责解析浏览器传过来的cookie

　浏览器负责：

　　　　　　　负责保存cookie

　　　　　　　负责将cookie发送给服务器

　　　　　　　浏览器一般只允许存放300个Cookie，每个站点最多存放20个Cookie（新版本的浏览器有所提升），每个Cookie的大小限制为4KB。

　Cookie常用方法:

　　　　　　　Cookie c = new Cookie(“”,“”) 构造方法

　　　　　　　c.getName()  获取cookie名

　　　　　　　c.getValue()  获取value值

　　　　　　　c.setMaxAge(int 秒)   设置存活时间

　　　　　　　setPath()　　　　设置有效路径

　　　　　　　Cookies[] cookie = request.getCookies(); 获得浏览器带来的cookie

　　　　　　　response.addCookie(cookie);将cookie带回浏览器
　　　　　　　
　　　　　　　乱码问题解决

　　　　　　　　　　编码：URLEncoder.encode(loginName,"utf-8");

　　　　　　　　　　解码：URLDecoder.decode("","UTF-8);

 

案例1  是否是第一次访问:

 1 import javax.servlet.ServletException;
 2 import javax.servlet.annotation.WebServlet;
 3 import javax.servlet.http.Cookie;
 4 import javax.servlet.http.HttpServlet;
 5 import javax.servlet.http.HttpServletRequest;
 6 import javax.servlet.http.HttpServletResponse;
 7 import java.io.IOException;
 8 import java.io.PrintWriter;
 9 @WebServlet(name = "w1",urlPatterns = "/w1")
10 public class work1 extends HttpServlet 
11     @Override
12     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
13         response.setContentType("text/html;charset=UTF-8");
14         Cookie[] cs = request.getCookies();
15         PrintWriter out = response.getWriter();
16 
17         boolean flag = false;
18 
19         if(cs!=null)
20             for(Cookie c:cs)
21                 if("visited".equals(c.getName()))
22                     flag = true;
23                     break;
24                 
25             
26         
27         if (flag)
28             out.println("欢迎回来");
29         else
30             out.println("第一次访问");
31             Cookie cookie = new Cookie("visited", "visit");
32             cookie.setMaxAge(24*60*60);
33             response.addCookie(cookie);
34         
35     
36     @Override
37     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
38         this.doPost(request, response);
39     
40 

 

案例2:   记录客户端上次访问时间:

 1 import javax.servlet.ServletException;
 2 import javax.servlet.annotation.WebServlet;
 3 import javax.servlet.http.Cookie;
 4 import javax.servlet.http.HttpServlet;
 5 import javax.servlet.http.HttpServletRequest;
 6 import javax.servlet.http.HttpServletResponse;
 7 import java.io.IOException;
 8 import java.io.PrintWriter;
 9 import java.time.LocalDateTime;
10 @WebServlet(name = "w2",urlPatterns = "/w2")
11 public class Work2 extends HttpServlet 
12     @Override
13     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
14         response.setContentType("text/html;charset=UTF-8");
15         Cookie[] cs = request.getCookies();
16         PrintWriter out = response.getWriter();
17         boolean flag = false;
18         Cookie cookie=null;
19         if(cs!=null)
20             for(Cookie c:cs)
21                 if("visited2".equals(c.getName()))
22                     flag = true;
23                     cookie=c;
24                     break;
25                 
26             
27         
28         if (flag)
29             out.print("欢迎回来");
30             out.print("<h1>上次访问时间为："+cookie.getValue()+"</h1>");
31         else
32             out.println("第一次访问");
33         
34         Cookie cookie1 = new Cookie("visited2", LocalDateTime.now().toString());
35         cookie.setMaxAge(24*60*60);
36         response.addCookie(cookie1);
37     
38     @Override
39     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
40         this.doPost(request, response);
41     
42 

案例3:   记录客户访问次数:

 1 import javax.servlet.ServletException;
 2 import javax.servlet.annotation.WebServlet;
 3 import javax.servlet.http.Cookie;
 4 import javax.servlet.http.HttpServlet;
 5 import javax.servlet.http.HttpServletRequest;
 6 import javax.servlet.http.HttpServletResponse;
 7 import java.io.IOException;
 8 import java.io.PrintWriter;
 9 import java.time.LocalDateTime;
10 @WebServlet(name = "w3",urlPatterns = "/w3")
11 public class work3 extends HttpServlet 
12     @Override
13     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
14         response.setContentType("text/html;charset=UTF-8");
15         Cookie[] cs = request.getCookies();
16         PrintWriter out = response.getWriter();
17 
18         boolean flag = false;
19         Cookie cookie=null;
20         if(cs!=null)
21             for(Cookie c:cs)
22                 if("visited3".equals(c.getName()))
23                     flag = true;
24                     cookie=c;
25                     break;
26                 
27             
28         
29         int i = 0;
30         if (flag)
31             i = Integer.parseInt(cookie.getValue());
32             out.print("欢迎回来");
33             out.print("<h1>访问次数为："+(++i)+"</h1>");
34         else
35             out.println("第一次访问");
36             Cookie cookie1 = new Cookie("visited3", 1+"");
37             cookie1.setMaxAge(24*60*60);
38             response.addCookie(cookie1);
39         
40         cookie = new Cookie("visited3", i+"");
41         response.addCookie(cookie);
42 
43     
44 
45     @Override
46     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
47         this.doPost(request, response);
48     
49 

案例4:   记录客户端用户名:

 1 @WebServlet(name = "username",urlPatterns = "/username")
 2 public class login extends HttpServlet 
 3     @Override
 4     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
 5         String loginName = request.getParameter("loginName");
 6         String password  = request.getParameter("pwd");
 7         String remember = request.getParameter("remember");
 8         int num = Integer.parseInt(remember);
 9 
10         if("123".equals(loginName.trim()) && "123".equals(password.trim()))
11             //登录成功,记录登录名
12             if(num!=0)
13                 String name = URLEncoder.encode(loginName, "UTF-8");// 编码
14                 Cookie c = new Cookie("loginName",name);
15                 c.setMaxAge(num*24*60*60);
16                 response.addCookie(c);
17             
18         else
19             response.sendRedirect("loginUsername.jsp");
20         
21     
22 
23     @Override
24     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
25         this.doPost(request,  response);
26     
27 

 

案例5:  记录用户的浏览记录:(网站的真实案例)

@WebServlet(name = "username",urlPatterns = "/username")
public class login extends HttpServlet 
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
        String loginName = request.getParameter("loginName");
        String password  = request.getParameter("pwd");
        String remember = request.getParameter("remember");
        int num = Integer.parseInt(remember);

        if("123".equals(loginName.trim()) && "123".equals(password.trim()))
            //登录成功,记录登录名
            if(num!=0)
                String name = URLEncoder.encode(loginName, "UTF-8");// 编码
                Cookie c = new Cookie("loginName",name);
                c.setMaxAge(num*24*60*60);
                response.addCookie(c);
            
        else
            response.sendRedirect("loginUsername.jsp");
        
    

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
        this.doPost(request,  response);
    


<%@ page import="com.cc.utils.CookieUtils" %>
<%@ page import="java.util.Arrays" %><%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2019/8/30
  Time: 16:26
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title></title>
  </head>
  <body>
    <a href="ServletView?id=1"><img src="img/1.jpg" />手电筒</a>
    <a href="ServletView?id=2"><img src="img/2.jpg" />手机</a>
    <a href="ServletView?id=3"><img src="img/3.jpg" />电视</a>
    <a href="ServletView?id=4"><img src="img/4.jpg" />冰箱</a>
    <a href="ServletView?id=5"><img src="img/5.jpg" />手表</a>
    <a href="ServletView?id=6"><img src="img/6.jpg" />电脑</a>
    <hr />
    <%
      Cookie[] cs = request.getCookies();
      Cookie c = CookieUtils.findCookieByName("product", cs);
      if(c!=null)
        String value = c.getValue();
        String[] ss = value.split(",");
        for(String str:ss)
    %>
    <img src="img/<%=str%>.jpg" width="150" height="100" />
    <%
        
      
    %>
  </body>
</html>


<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title></title>
</head>
<body>
   <%
       String id = (String)request.getAttribute("id");
   %>
   <img src="img/<%=id %>.jpg" width="300" height="400" />
   <a href="index.jsp">返回首页</a>
</body>
</html>

 

session

和cookie的区别
　　1 Cookie有大小和个数的限制的.  Session存在服务器端没有大小和个数的限制.
　　2 Cookie存到客户端上 信息不安全.  Session的数据相对来说安全.

　　　3.Session运行原理也是基于Cookie ：利用Cookie回写一个 JSESSIONID 

　session方法

　　　HttpSession session = request.getSession();  创建session

　　　HttpSession session = request.getSession(false);  若没有创建,返回null

　　　session.getId(); 获取session的ID;

　　　session.setAttribute("",Object);  　写入信息

   　session.getAttribute("");   获取信息

   　session.removeAttribute("");  移除信息

　session的销毁

　　　1.关闭服务器（非正常关闭服务器）

　　　2.session时间到期 session的默认存活时间是30分钟

　　　3.调用session 的  invalidate()方法

　典型应用

　　　Web工程HttpSession的最典型应用是，登录时，当登录成功后，把登录用户的对象保存在Session中，保证一次会话该用户的状态。退出登录时，把该用户从Session中清除。

　Session和Cookie的区别和联系

　　 　1.数据存储的位置不同 Cookie在客户端 Session在服务器端

      2.生命周期不同,Cookie（会话Cookie浏览器关闭   持久化Cookie setMaxAge(秒数)）Session(默认30分钟，可以修改)

      3.cookie只能存放字符串名值对，session可以是任意对象

      4.同一个浏览器接受cookie的个数是有上限

 

案例1  是否是第一次访问:

public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException 
        String str = "";
        HttpSession session = request.getSession(false);
        if(session==null)
            str = "第一次访问";
            session = request.getSession();
        else            
            str = "欢迎回来";
        
        response.setContentType("text/html;charset=utf-8");
        PrintWriter out = response.getWriter();
        out.println(str);    
    

 

案例2  典型应用登录后保存用户信息:

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        UserService service = new  UserServiceImpl();
        response.setContentType("text/html;charset=utf-8");
        User user = service.login(username, password);
        ServletContext sc= this.getServletContext();
        if(user!=null)
            //传入session
            HttpSession session = request.getSession(false);
            session.setAttribute("user",user);
            response.sendRedirect("welcome.jsp");
        else
            response.sendRedirect("login.jsp");
        
    

 

<%@ page import="com.cc.bean.User" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>
<title>Insert title here</title>
<script>
    function changeImage()
        document.getElementById(‘checkImage‘).src="CheckCodeServlet?aaa="+Math.random();
    
</script>
</head>
<body>
<%
    User user = (User)session.getAttribute("user");
    String str = "";
    if (user!=null)
        str = user.getUsername();
        System.out.println(str);
    
%>
<form action="Servlet" method="post">
    username:<input type="text" name="username" value="<%=str%>"/><br/>
    password:<input type="password" name="password" /><br/>
    验证码:<input type="text" size="10" /><img src="CheckCodeServlet" id="checkImage" /><a href="javascript:changeImage()">看不清，换一张</a><br/>
    <input type="submit" value=" login " />
</form>

</body>
</html>