Cookie&Session10_Session2

Session:主菜

1.概念

  服务器端会话技术,在一次会话的多次请求间共享数据,将数据保存在服务器端的对象中。HttpSession

2. 快速入门

  HttpSession也是域对象

  a. 获取HttpSession对象:

      HttpSession session = request.getSession();

  b. 使用HttpSession对象:

      Object getAttribute(String name)  

      void setAttribute(String name, Object value)

      void removeAttribute(String name)  

package cn.itcast.session;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet("/sessionDemo1")
public class SessionDemo1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //使用session共享数据
        //1. 获取session
        HttpSession session = request.getSession();

        //2. 存储数据
        session.setAttribute("msg","hello session");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}
package cn.itcast.session;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet("/sessionDemo2")
public class SessionDemo2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //使用session共享数据
        //1. 获取session
        HttpSession session = request.getSession();

        //2. 获取数据
        Object msg = session.getAttribute("msg");
        System.out.println(msg);
    }

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

    浏览器访问http://localhost/day10/sessionDemo1,然后访问http://localhost/day10/sessionDemo2,检查idea控制台输出:hello session。

    关闭浏览器,重新打开浏览器访问http://localhost/day10/sessionDemo2,检查idea控制台输出:null

3. 原理

  Session的实现是依赖于Cookie的。

  

  浏览器访问http://localhost/day10/sessionDemo1,检查响应头

  

  浏览器访问http://localhost/day10/sessionDemo2,检查请求头

   

  两个的JSESSIONID是一样的。

4. 当客户端关闭后,服务器不关闭,两次获取session是否为同一个?

  a. 默认情况下不是。因为客户端关闭意味着会话结束了

  b. 如果需要相同,则可以创建Cookie,键为JSESSIONID,设置最大存活时间,让cookie持久化保存。

    Cookie c = new Cookie("JSESSIONID",session.getId());

    c.setMaxAge(60*60);

    response.addCookie(c);

  代码实现一:默认情况下关闭客户端,两次获取session不同

package cn.itcast.session;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet("/sessionDemo3")
public class SessionDemo3 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. 获取session
        HttpSession session = request.getSession();

        System.out.println(session);
    }

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

    浏览器访问http://localhost/day10/sessionDemo3,关闭浏览器,打开浏览器重复访问,检查idea控制台输出session对象的地址栏不同,可以证明不是同一个session对象。当然如果不关闭浏览器重复访问,则是同一个session对象

    

   代码实现二:

package cn.itcast.session;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;

@WebServlet("/sessionDemo3")
public class SessionDemo3 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. 获取session
        HttpSession session = request.getSession();
        System.out.println(session);

        //期望客户端关闭后,session也能相同
        Cookie cookie = new Cookie("JSESSIONID", session.getId());
        cookie.setMaxAge(60*60);
        response.addCookie(cookie);
    }

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

    浏览器访问http://localhost/day10/sessionDemo3,关闭浏览器,打开浏览器重复访问,检查idea控制台输出的session对象的地址是一样的,表示是同一个session。

    

5. 客户端不关闭,服务器关闭后,两次获取的session是同一个吗?

  不是同一个,但是要确保数据不丢失。tomcat自动完成以下工作

    * session的钝化(序列化过程):

      * 在服务器正常关闭之前,将session对象序列化到硬盘上

    * session的活化(反序列化过程):

      * 在服务器启动后,将session文件转化为内存中的session对象即可。

    idea不能演示出session的钝化和活化。要使用本地的tomcat进行演示完成。

  演示一:

package cn.itcast.session;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;

@WebServlet("/sessionDemo4")
public class SessionDemo4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. 获取session
        HttpSession session = request.getSession();
        System.out.println(session);

    }

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

  浏览器访问http://localhost/day10/sessionDemo4,检查idea控制台输出session对象的地址值:org.apache.catalina.session.StandardSessionFacade@34de66e7。关闭tomcat服务器后启动tomcat服务器,浏览器再次访问,检查idea控制台输出:org.apache.catalina.session.StandardSessionFacade@72a5ebd7。

  由此可见,两次获取的session不是同一个。

  演示二:

    idea不能演示出session的钝化和活化。要使用本地的tomcat进行演示完成。

    本地的tomcat演示步骤:

    把项目的真实路径,即out文件中的项目路径下的项目文件打包成war包,放到tomcat的webapps,startup.bat启动tomcat后,浏览器访问http://localhost:8080/day10/sessionDemo1,然后访问http://localhost:8080/day10/sessionDemo2,可以看到tomcat终端输出:hello session。

    这时点击shupdown.bat正常关闭tomcat,可以看到tomcat的work-Catilina-localhost-day10目录下就会生成一个SESSIONS.ser文件。文件中放的是session对象。

    把tomcat服务器重动,这个文件会被自动读取,并且这个文件被删除掉,把文件中的内容还原到内存中了。虽然对象的地址值不一样,但是sessionId是一样的。这时候访问http://localhost:8080/day10/sessionDemo1,仍旧能输出hello session。

   idea演示步骤:

    启动tomat,浏览器访问http://localhost:8080/day10/sessionDemo1,idea中关闭tomat服务后,CATALINA_BASE下的work-Catalina-localhost-day10下会生成SESSIONS.ser文件。idea中启动tomcat可以发现会先把CATALINA_BASE下的work文件夹删除,然后新建一个work,这样就找不到原来的SESSIONS.ser文件了。

6. session什么时候被销毁?

  a. 服务器关闭

  b. session对象调用invalidate() 。

  c. session默认失效时间 30分钟

    tomcat-conf-web.xml中选择性配置修改

    <session-config>

      <session-timeout>30</session-timeout>

    </session-config>

7. session的特点

  a. session用于存储一次会话的多次请求的数据,存在服务器端

  b. session可以存储任意类型,任意大小的数据

8. session与Cookie的区别:

  a. session存储数据在服务器端,Cookie在客户端

  b. session没有数据大小限制,Cookie有

  c. session数据安全,Cookie相对于不安全

9. 案例:验证码

  需求:

    a. 访问带有验证码的登录页面login.jsp

    b. 用户输入用户名,密码以及验证码。

      * 如果用户名和密码输入有误,跳转登录页面,提示:用户名或密码错误

      * 如果验证码输入有误,跳转登录页面,提示:验证码错误

      * 如果全部输入正确,则跳转到主页success.jsp,显示:用户名,欢迎您

  分析:

    

  实现:

package cn.itcast.domain;

/**
 * 用户的实体类
 */
public class User {
    private int id;
    private String username;
    private String password;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    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;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

druid.properties放在src下

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql:///day08
username=root
password=root
initialSize=5
maxActive=10
maxWait=3000
package cn.itcast.utils;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

/**
 * JDBC工具类 使用Druid连接池
 */
public class JDBCUtils {

    private static DataSource ds;

    static {
        try {
            //1. 加载配置文件
            Properties pro = new Properties();
            //使用ClassLoader加载配置i文件,获取字节输入流
            InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");

            pro.load(is);

            //2. 初始化连接池对象
            ds = DruidDataSourceFactory.createDataSource(pro);

        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }


    }
    /**
     * 获取连接池对象
     */
    public static DataSource getDataSource(){
        return ds;
    }


    /**
     * 获取连接Connection对象
     */
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }
}
package cn.itcast.dao;

import cn.itcast.domain.User;
import cn.itcast.util.JDBCUtils;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

/**
 * 操作数据库中User表的类
 */
public class UserDao {

    //声明JDBCTemplate对象公用
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

    /**
     * 登录方法
     * @param loginUser 只有用户名和密码
     * @return user包含用户全部数据,没有查询到返回null
     */
    public User login(User loginUser){
        try {
            //1. 编写sql
            String sql ="select * from user where username=? and password=?";
            //2. 调用query方法
            User user = template.queryForObject(sql,
                    new BeanPropertyRowMapper<User>(User.class),
                    loginUser.getUsername(),
                    loginUser.getPassword());
            return user;
        } catch (DataAccessException e) {
            e.printStackTrace();//记录日志
            return null;
        }
    }
} 

login.jsp

<%--
  Created by IntelliJ IDEA.
  User: ajing
  Date: 2022/2/26
  Time: 20:42
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>login</title>
    <script>
        window.onload = function(){
            document.getElementById("img").onclick = function () {
                this.src="/day10/checkCodeServlet?time="+ new Date().getTime();
            }
        }
    </script>

    <style>
        div{
            color: red;
        }
    </style>
</head>
<body>

    <form action="/day10/loginServlet" method="post">
        <table>
            <tr>
                <td>用户名</td>
                <td><input type="text" name="username"></td>
            </tr>
            <tr>
                <td>密码</td>
                <td><input type="text" name="password"></td>
            </tr>
            <tr>
                <td>验证码</td>
                <td><input type="text" name="checkCode"></td>
            </tr>
            <tr>
                <td colspan="2"><img id="img" src="/day10/checkCodeServlet"></td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" value="登录"></td>
            </tr>
        </table>
    </form>

    <div><%=request.getAttribute("cc_error")%></div>
    <div><%=request.getAttribute("login_error")%></div>

</body>
</html>

  success.jsp

<%--
  Created by IntelliJ IDEA.
  User: ajing
  Date: 2022/2/26
  Time: 21:15
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

    <h1><%=request.getSession().getAttribute("user")%>,欢迎您</h1>

</body>
</html>
package cn.itcast.servlet;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;


@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        int width = 100;
        int height = 50;

        //1. 创建一个对象,在内存中图片(代表验证码图片对象)
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);//在浏览器输出一张宽100高50的黑色背景的图片

        //2. 美化图片
        //2.1 填充背景色
        Graphics g = image.getGraphics();//获取画笔对象
        g.setColor(Color.PINK);//设置画笔颜色
        g.fillRect(0,0,width,height);

        //2.2 画边框
        g.setColor(Color.BLUE);
        g.drawRect(0,0,width-1,height-1);

        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        //生成随机角标
        Random ran = new Random();
        StringBuilder sb = new StringBuilder();

        for (int i = 1; i <= 4; i++) {
            int index = ran.nextInt(str.length());
            //获取字符
            char ch = str.charAt(index);//随机字符
            sb.append(ch);
            //2.3 写验证码
            g.drawString(ch+"",width/5*i,height/2);
        }

        String checkCode_session = sb.toString();
        //将验证码存入session
        request.getSession().setAttribute("checkCode_session",checkCode_session);

        //2.4 画干扰线
        g.setColor(Color.GREEN);

        //随机生成坐标点

        for (int i = 0; i < 10; i++) {
            int x1 = ran.nextInt(width);
            int x2 = ran.nextInt(width);

            int y1 = ran.nextInt(height);
            int y2 = ran.nextInt(height);
            g.drawLine(x1,y1,x2,y2);
        }

//        g.drawLine(1,1,30,30);

        //3. 将图片输出到页面展示
        ImageIO.write(image,"jpg",response.getOutputStream());

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}
package cn.itcast.servlet;

import cn.itcast.dao.UserDao;
import cn.itcast.domain.User;
import org.apache.commons.beanutils.BeanUtils;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. 设置request编码
        request.setCharacterEncoding("utf-8");
        //2. 获取参数Map
        Map<String, String[]> map = request.getParameterMap();

        //3. 创建User对象
        User loginUser = new User();
        UserDao dao = new UserDao();
        try {
            BeanUtils.populate(loginUser,map);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        //3. 先获取生产的验证码
        HttpSession session = request.getSession();
        String checkCode_session = (String) session.getAttribute("checkCode_session");


        //3.先判断验证码是否正确
        if(checkCode_session.equalsIgnoreCase(map.get("checkCode")[0])){
            //忽略大小写比较
            //验证码正确
            //判断用户名和密码是否一致

            //4. 调用UserDao的login方法
            User user = dao.login(loginUser);

            if(user != null){
                //登录成功
                //存储信息:用户信息
                session.setAttribute("user",user.getUsername());

                //重定向到success.jsp
                response.sendRedirect(request.getContextPath()+"/success.jsp");
            }else {
                //登录失败
                //存储提示信息到request
                request.setAttribute("login_error","用户名或密码错误");
                //转发到登录页面
                request.getRequestDispatcher("/login.jsp").forward(request,response);
            }
        }else{
            //验证码不一致
            //存储提示信息到request
            request.setAttribute("cc_error","验证码错误");
            //转发到登录页面
            request.getRequestDispatcher("/login.jsp").forward(request,response);
        }
    }

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

  浏览器访问http://localhost/day10/login.jsp,检查浏览器展示:

  

    输入错误的验证码,点击登录,检查浏览器展示:

  

  输入正确的验证码,输入错误的用户名和密码,点击登录,检查浏览器展示:

  

  输入正确的验证码,输入正确的用户名和密码,点击登录,检查浏览器展示:

  

  解决bug:

  1、null展示的问题

    修改login.jsp:

    <div><%=request.getAttribute("cc_error") == null ? "":request.getAttribute("cc_error")%></div>
    <div><%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error")%></div>

  2、输入正确的用户名、密码和验证码,从成功页后退到登录页面验证码没有变,也就是没有重新请求。这样我用原来的验证码仍旧会登录成功。这样不太安全。

  修改LoginServlet中的部分代码

     HttpSession session = request.getSession();
        String checkCode_session = (String) session.getAttribute("checkCode_session");

        //删除session中存储的验证码
        session.removeAttribute("checkCode_session");

        //3.先判断验证码是否正确
        if(checkCode_session != null && checkCode_session.equalsIgnoreCase(map.get("checkCode")[0])){

  这时候后退后虽然验证码看着没变,但是用这个验证码点击登录会报:验证码错误

 

posted on 2022-02-26 01:32  花溪月影  阅读(26)  评论(0编辑  收藏  举报