08-2 Session

时间 2019-11-15

原文原文链接

第5节 Session快速入门

Session快速入门

1. 概念：服务器端会话技术，在一次会话的屡次请求间共享数据，将数据保存在服务器端的对象中。HttpSession
2. 快速入门：
    1. 获取HttpSession对象：
        HttpSession session = request.getSession();
    2. 使用HttpSession对象：
        Object getAttribute(String name)  
        void setAttribute(String name, Object value)
        void removeAttribute(String name)

package cn.itcast.session;html

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;java

@WebServlet("/sessionDemo1")
public class SessionDemo1 extends HttpServlet {web

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;数据库

@WebServlet("/sessionDemo2")
public class SessionDemo2 extends HttpServlet {tomcat

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //使用session获取数据

    //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);
}

}安全

Session原理分析

Session的实现是依赖于Cookie的。

第6节 Session细节

当客户端关闭后，服务器不关闭，两次获取session是否为同一个？

* 默认状况下。不是。
        * 若是须要相同，则能够建立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);

package cn.itcast.session;服务器

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

@WebServlet("/sessionDemo3")
public class SessionDemo3 extends HttpServlet {session

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    //1.获取session
    HttpSession session = request.getSession();
    System.out.println(session);
    //以上关闭浏览器后再执行打印的session不是同一个,可是设置了下边的代码之后打印的session是同一个了

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

}

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.*;
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);
}

}

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，可是要确保数据不丢失。tomcat自动完成如下工做
            * session的钝化：
                * 在服务器正常关闭以前，将session对象系列化到硬盘上
            * session的活化：
                * 在服务器启动后，将session文件转化为内存中的session对象便可。

将out工做目录下的项目打包成war文件夹

把war文件夹放到tomcat的webapp目录

关掉idea本地的tomcat
启动tomcat
访问locahost:8080/day16/sessionDemo1
而后访问localhost:8080/day16/sessionDemo2

正常关闭服务器

从新启动后session的序列化文件删除内容从新还原到内存中了

那么在idea的Catalina_base的目录是相似于
C:UsersAdministrator.IntelliJIdea2019.2systemtomcat_learn

在idea重启tomcat的目录的时候会把work目录删掉

等一会会建立一个work文件，可是文件中没有对应的session文件了

session何时被销毁？

1. 服务器关闭
        2. session对象调用invalidate() 。
        3. session默认失效时间 30分钟
            选择性配置修改    
            <session-config>
                <session-timeout>30</session-timeout>
            </session-config>

session的特色

1. session用于存储一次会话的屡次请求的数据，存在服务器端
     2. session能够存储任意类型，任意大小的数据

    * session与Cookie的区别：
        1. session存储数据在服务器端，Cookie在客户端
        2. session没有数据大小限制，Cookie有
        3. session数据安全，Cookie相对于不安全

第7节 Session之验证码案例

login.jsp

<%@ 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="/day16/checkCodeServlet?time="+new Date().getTime();
        }
    }


</script>
<style>
    div{
        color: red;
    }

</style>

</head>
<body>

<form action="/day16/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="password" 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="/day16/checkCodeServlet"></td>
        </tr>
        <tr>
            <td colspan="2"><input type="submit" value="登陆"></td>
        </tr>
    </table>


</form>


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

</body>
</html>

success.jsp

<%@ 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>

LoginServlet.java

package cn.itcast.servlet;

@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
    String username = request.getParameter("username");
    String password = request.getParameter("password");
    String checkCode = request.getParameter("checkCode");
    //3.先获取生成的验证码
    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(checkCode)){
        //忽略大小写比较
        //验证码正确
        //判断用户名和密码是否一致
        if("zhangsan".equals(username) && "123".equals(password)){//须要调用UserDao查询数据库
            //登陆成功
            //存储信息，用户信息
            session.setAttribute("user",username);
            //重定向到success.jsp
            response.sendRedirect(request.getContextPath()+"/success.jsp");
        }else{
            //登陆失败
            //存储提示信息到request
            request.setAttribute("login_error","用户名或密码错误");
            //转发到登陆页面
            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");
        //转发到登陆页面
        request.getRequestDispatcher("/login.jsp").forward(request,response);

    }

}

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

}

CheckCodeServlet.java

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.建立一对象，在内存中图片(验证码图片对象)
    BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);


    //2.美化图片
    //2.1 填充背景色
    Graphics g = image.getGraphics();//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 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
    //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);
    }


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


}

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

}