Session详解，学习 Session对象一篇文章就够了

目录

1 Session概述

2 Session原理

3 Session使用

3.1 获取Session

3.2 Session保存数据

3.3 Session获取数据

3.4 Session移除数据

4 Session与Request应用区别

4.1 Session和request存储数据

4.2 获取session和request中的值

4.3 session和request区别效果

5 Session的声明周期

5.1 Session有效时间设置

5.2 session销毁

.6 浏览器禁用Cookie解决方案（了解）

6.1 浏览器禁用Cookie的后果

6.2 URL重写

6.3 实现URL重写

7 Session实战权限验证

7.1 创建管理员表manager并添加数据

7.2 创建Web项目

7.3 基础环境搭建

7.4 登录页面

7.5 LoginMgrController

7.6 ShowAllManagerController

7.7 ShowAllManagerJsp

8 Session实战保存验证码

8.1 创建验证码

8.2 登录页面

8.3 LoginMgrController

8.4 ShowAllManagerController

今天的分享就到此结束了

创作不易点赞评论互关三连

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1 Session概述

（1）Session用于记录用户的状态。Session指的是一段时间内，单个客户端与Web服务器的一连串相关的交互过程。

（2）在一个Session中，客户可能会多次请求访问同一个资源，也有可能请求访问各种不同的服务器资源。

（3）Session是由服务器端创建的

2 Session原理

（1）Session会为每一次会话分配一个Session对象

（2）同一个浏览器发起的多次请求，同属于一次会话（Session）

（3）首次使用到Session时，服务器会自动创建Session，并创建Cookie存储SessionId发送回客户端

3 Session使用

Session作用域：拥有存储数据的空间，作用范围是一次会话有效

• 一次会话是使用同一浏览器发送的多次请求。一旦浏览器关闭，则结束会话

• 可以将数据存入Session中，在一次会话的任意位置进行获取

• 可传递任何数据（基本数据类型、对象、集合、数组）

3.1 获取Session

Session是服务器端自动创建的，通过request对象获取

package com.cxyzxc.www.servlet01;

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

@WebServlet(name = "SessionServlet01", value = "/SessionServlet01")
public class SessionServlet01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置请求参数的编码格式，这种方式对get请求方式无效
        request.setCharacterEncoding("UTF-8");
        //设置响应编码格式为UTF-8
        response.setContentType("text/html;charset=UTF-8");

        //获取Session对象,首次使用到Session时，服务器会自动创建Session，并创建Cookie存储SessionId发送回客户端
        HttpSession session = request.getSession();
        System.out.println("ID:" + session.getId());//唯一标记

    }

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

3.2 Session保存数据

使用setArrtibute(属性名,Object)保存数据到session中

package com.cxyzxc.www.servlet01;

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(name = "SessionServlet02", value = "/SessionServlet02")
public class SessionServlet02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置请求参数的编码格式，这种方式对get请求方式无效
        request.setCharacterEncoding("UTF-8");
        //设置响应编码格式为UTF-8
        response.setContentType("text/html;charset=UTF-8");

        //获取Session对象,首次使用到Session时，服务器会自动创建Session，并创建Cookie存储SessionId发送回客户端
        HttpSession session = request.getSession();

        //将数据存储以键值对的形式到session对象中，可传递任何数据（基本数据类型、对象、集合、数组）
        session.setAttribute("username","张三");

    }

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

 

3.3 Session获取数据

（1）使用getAttribute("属性名");获取session中数据。

（2）先访问SessionServlet02将数据存储到session对象中，然后通过GetSessionValueServlet01请求获取session中的数据

package com.cxyzxc.www.servlet01;

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

@WebServlet(name = "GetSessionValueServlet01", value = "/GetSessionValueServlet01")
public class GetSessionValueServlet01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置请求参数的编码格式，这种方式对get请求方式无效
        request.setCharacterEncoding("UTF-8");
        //设置响应编码格式为UTF-8
        response.setContentType("text/html;charset=UTF-8");

        //获取Session对象
        HttpSession session = request.getSession();
        //获取session对象中的值，获取的值是Object类型，转换为其对应的类型
        String username = (String) session.getAttribute("username");
        System.out.println("session对象中存储的username值：" + username);
    }

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

3.4 Session移除数据

（1）使用removeAttribute("属性名");从session中删除数据

（2）向请求SessionServlet02向session对象中存储数据，然后访问GetSessionValueServlet01可以获取session对象中的值，再访问SessionServlet03移除session对象中存储的数据，最后访问GetSessionValueServlet01获取session对象中的值为null

package com.cxyzxc.www.servlet01;

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(name = "SessionServlet03", value = "/SessionServlet03")
public class SessionServlet03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置请求参数的编码格式，这种方式对get请求方式无效
        request.setCharacterEncoding("UTF-8");
        //设置响应编码格式为UTF-8
        response.setContentType("text/html;charset=UTF-8");

        //获取Session对象,首次使用到Session时，服务器会自动创建Session，并创建Cookie存储SessionId发送回客户端
        HttpSession session = request.getSession();

        //通过键移除session作用域中的值
        session.removeAttribute("username");

    }

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

 

4 Session与Request应用区别

（1）request是一次请求有效，请求改变，则request改变

（2）session是一次会话有效，浏览器改变，则session改变

4.1 Session和request存储数据

package com.cxyzxc.www.servlet01;

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(name = "SessionServlet04", value = "/SessionServlet04")
public class SessionServlet04 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置请求参数的编码格式，这种方式对get请求方式无效
        request.setCharacterEncoding("UTF-8");
        //设置响应编码格式为UTF-8
        response.setContentType("text/html;charset=UTF-8");

        //获取Session对象
        HttpSession session = request.getSession();

        //使用session存储数据
        session.setAttribute("username","zhangsan");
        //使用request存储数据
        request.setAttribute("password","123456");

        //重定向
        response.sendRedirect("/webProject10_war_exploded/GetSessionValueServlet01");

    }

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

 

4.2 获取session和request中的值

package com.cxyzxc.www.servlet01;

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(name = "GetSessionValueServlet01", value = "/GetSessionValueServlet01")
public class GetSessionAndRequestValueServlet01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置请求参数的编码格式，这种方式对get请求方式无效
        request.setCharacterEncoding("UTF-8");
        //设置响应编码格式为UTF-8
        response.setContentType("text/html;charset=UTF-8");

        //获取Session对象
        HttpSession session = request.getSession();
        //获取session对象中的值，获取的值是Object类型，转换为其对应的类型
        String username = (String) session.getAttribute("username");
        //获取request对象中的值，获取的值是Object类型，转换为其对应的类型
        String password = (String) request.getAttribute("password");

        System.out.println("session对象中存储的username值：" + username);
        System.out.println("request对象中存储的password值：" + password);
    }

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

4.3 session和request区别效果

5 Session的声明周期

1. 开始

   第一次使用到Session的请求产生，则创建Session

2. 结束

   • 浏览器关闭，则失效

   • Session超时，则失效

     session.setMaxInactiveInterval(seconds);//设置最大有效时间（单位：秒）

   • 手工销毁，则失效

     session.invalidate();//登录退出，销毁

5.1 Session有效时间设置

SessionServlet05类设置session有效期为20秒，先通过请求SessionServlet05类将session存储在，然后在20秒内第一次在GetSessionValueServlet02获取sessionID值，与SessionServlet05类中输出的id值一致，过20秒后在GetSessionValueServlet02类中输出的sessionID值不一致了

 

package com.cxyzxc.www.servlet01;

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(name = "SessionServlet05", value = "/SessionServlet05")
public class SessionServlet05 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置请求参数的编码格式，这种方式对get请求方式无效
        request.setCharacterEncoding("UTF-8");
        //设置响应编码格式为UTF-8
        response.setContentType("text/html;charset=UTF-8");

        //获取Session对象,首次使用到Session时，服务器会自动创建Session，并创建Cookie存储SessionId发送回客户端
        HttpSession session = request.getSession();

        //设置session有效期,时间单位为秒
        session.setMaxInactiveInterval(20);

        //输出sessionid值
        System.out.println("SessionServlet05类中输出ID:"+session.getId());

    }

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

5.2 session销毁

先使用GetSessionValueServlet03类获取session的id值，然后使用GetSessionValueServlet04类获取session的id值，两个类获取的id值一致，在GetSessionValueServlet04类中输出id值后销毁了session，然后再在GetSessionValueServlet03类中获取id值，就不一致了，就是服务器新建的session对象了

5.2.1 GetSessionValueServlet03类

package com.cxyzxc.www.servlet01;

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(name = "GetSessionValueServlet03", value = "/GetSessionValueServlet03")
public class GetSessionValueServlet03 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置请求参数的编码格式，这种方式对get请求方式无效
        request.setCharacterEncoding("UTF-8");
        //设置响应编码格式为UTF-8
        response.setContentType("text/html;charset=UTF-8");

        //获取Session对象
        HttpSession session = request.getSession();

        //输出sessionid值
        System.out.println("GetSessionValueServlet03类中输出ID:"+session.getId());

    }

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

 

5.2.2 GetSessionValueServlet04类

package com.cxyzxc.www.servlet01;

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(name = "GetSessionValueServlet04", value = "/GetSessionValueServlet04")
public class GetSessionValueServlet04 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置请求参数的编码格式，这种方式对get请求方式无效
        request.setCharacterEncoding("UTF-8");
        //设置响应编码格式为UTF-8
        response.setContentType("text/html;charset=UTF-8");

        //获取Session对象
        HttpSession session = request.getSession();

        //输出sessionid值
        System.out.println("GetSessionValueServlet04类中输出ID:"+session.getId());

        //销毁session
        session.invalidate();

    }

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

.6 浏览器禁用Cookie解决方案（了解）

6.1 浏览器禁用Cookie的后果

服务器在默认情况下，会使用Cookie的方式将sessionID发送给浏览器，如果用户禁止Cookie，则sessionID不会被浏览器保存，此时，服务器可以使用URL重写这样的方式来发送sessionID

 

多次请求GetSessionValueServlet05类输出的session的id值都不相同，并且在网站的Cookie对象中没有session的id值存在

 

6.2 URL重写

浏览器在访问服务器上的某个地址时，不再使用原来的那个地址，而是使用经过改写的地址（即在原来的地址后面加上了sessionID）

6.3 实现URL重写

response.encodeRedirectURL(String url)生成重写的URL

6.3.1 重写URL

package com.cxyzxc.www.servlet01;

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(name = "GetSessionValueServlet06", value = "/GetSessionValueServlet06")
public class GetSessionValueServlet06 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置请求参数的编码格式，这种方式对get请求方式无效
        request.setCharacterEncoding("UTF-8");
        //设置响应编码格式为UTF-8
        response.setContentType("text/html;charset=UTF-8");

        //获取Session对象
        HttpSession session = request.getSession();

        //输出sessionid值
        System.out.println("GetSessionValueServlet06类中输出ID:"+session.getId());

        //重写URL追加session值
        String newURL = response.encodeURL("/webProject10_war_exploded/GetSessionValueServlet07");
        System.out.println("重写后的URL："+newURL);
        //重定向
        response.sendRedirect(newURL);

    }

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

 

6.3.1 获取session

package com.cxyzxc.www.servlet01;

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(name = "GetSessionValueServlet07", value = "/GetSessionValueServlet07")
public class GetSessionValueServlet07 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置请求参数的编码格式，这种方式对get请求方式无效
        request.setCharacterEncoding("UTF-8");
        //设置响应编码格式为UTF-8
        response.setContentType("text/html;charset=UTF-8");

        //获取Session对象
        HttpSession session = request.getSession();

        //输出sessionid值
        System.out.println("GetSessionValueServlet07类中输出ID:"+session.getId());


    }

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

7 Session实战权限验证

 

7.1 创建管理员表manager并添加数据

 

7.2 创建Web项目

创建Web项目，导入相关jar包

• commons-dbutils-1.7.jar

• druid-1.1.5.jar

• mysql-connector-java-5.1.25-bin.jar

• servlet-api.jar

7.3 基础环境搭建

在项目下创建包目录结构如下

• com.cxyzxc.www.controller包：调用业务逻辑Servlet

• com.cxyzxc.www.dao包：数据访问层接口

• com.cxyzxc.www.dao.impl包：数据访问层接口实现类

• com.cxyzxc.www.entity包：实体类

• com.cxyzxc.www.jsp包：打印显示页面Servlet

• com.cxyzxc.www.service包：业务逻辑层接口

• com.cxyzxc.www.service.impl包：业务逻辑层接口实现类

• com.cxyzxc.www.utils包：工具类

• database.properties:数据库连接及连接池配置文件

7.4 登录页面

7.4.1 login.html

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>管理员登录页面</title>
        <link type="text/css" rel="stylesheet" href="css/login.css"/>
    </head>

    <body>
        <div>
            <form action="LoginMgrController" method="post">
                <p>
                    账号：<input type="text" name="username"/>
                </p>
                <p>
                    密码：<input type="password" name="password"/>
                </p>
                <p>
                    <input type="submit" value="登录"/>
                </p>
            </form>
        </div>
    </body>
</html>

 

7.4.2 login.css

* {
    margin: 0;
    padding: 0;
}

div {
    width: 400px;
    background-color: #ccc;
    margin: 30px auto;
    padding-top: 30px;
    text-align: center;
}

p {
    margin-top: 10px;
}

input {
    outline: none;
}

7.5 LoginMgrController

package com.cxyzxc.www.controller;

import com.cxyzxc.www.entity.Manager;
import com.cxyzxc.www.service.ManagerService;
import com.cxyzxc.www.service.impl.ManagerServiceImpl;

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

@WebServlet(name = "LoginMgrController", value = "/LoginMgrController")
public class LoginMgrController extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1、处理乱码
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

        //2、收参（获取客户端发送过来的请求数据）
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        //3、调用业务方法
        ManagerService managerService = new ManagerServiceImpl();
        Manager manager = managerService.login(username, password);


        //4、处理结果，根据结果做不同的跳转
        if (manager != null) {//manager不为null，说明账号和密码正确，登录成功
            //将获取的账号和密码信息存储在session中
            HttpSession session = request.getSession();
            session.setAttribute("manager", manager);
            //跳转到显示所有管理员信息的Servlet
            response.sendRedirect("/managerProject01_war_exploded/ShowAllManagerController");
        } else {//manager为null。说明账号或者密码错误，登录失败
            response.sendRedirect("/managerProject01_war_exploded/login.html");
        }


    }

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

7.6 ShowAllManagerController

package com.cxyzxc.www.controller;

import com.cxyzxc.www.entity.Manager;
import com.cxyzxc.www.service.ManagerService;
import com.cxyzxc.www.service.impl.ManagerServiceImpl;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.List;

@WebServlet(name = "ShowAllManagerController", value = "/ShowAllManagerController")
public class ShowAllManagerController extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1、处理乱码
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

        //通过HttpSession完成权限控制
        HttpSession session =request.getSession();
        //获取session中存储的值
        Manager manager = (Manager)session.getAttribute("manager");
        //判断获取的值
        if(manager!=null){
            //调用业务,只做业务，业务与显示分离
            ManagerService managerService = new ManagerServiceImpl();
            List<Manager> managers =managerService.showAllManager();
            //将获取的数据存储在request作用域中
            request.setAttribute("managers",managers);
            //转发，跳转到显示结果的Servlet
            request.getRequestDispatcher("/ShowAllManagerJsp").forward(request,response);
        }else{
            //说明没有登录，要先去登录才能进行显示
            response.sendRedirect("/managerProject01_war_exploded/login.html");
        }
    }

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

7.7 ShowAllManagerJsp

package com.cxyzxc.www.jsp;

import com.cxyzxc.www.entity.Manager;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

@WebServlet(name = "ShowAllManagerJsp", value = "/ShowAllManagerJsp")
public class ShowAllManagerJsp extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1、处理乱码
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

        //2、获取数据
        List<Manager> managers = (List<Manager>) request.getAttribute("managers");

        //获取输出流
        PrintWriter printWriter = response.getWriter();
        if (managers.size() != 0) {
            printWriter.println("<html>");
            printWriter.println("<head>");
            printWriter.println("<title>所有管理员</title>");
            printWriter.println("<link type=\"text/css\" rel=\"stylesheet\" href=\"css/table.css\" />");
            printWriter.println("</head>");
            printWriter.println("<table border='1px' cellspacing='0'>");
            printWriter.println("<tr>");
            printWriter.println(" <th>序号</th>");
            printWriter.println(" <th>账号</th>");
            printWriter.println(" <th>密码</th>");
            printWriter.println(" <th>操作</th>");
            printWriter.println(" </tr>");
            for (int i = 0; i < managers.size(); i++) {
                printWriter.println("<tr>");
                printWriter.println("<td>" + (i + 1) + "</td>");
                printWriter.println("<td>" + managers.get(i).getUsername() + "</td>");
                printWriter.println("<td>" + managers.get(i).getPassword() + "</td>");
                printWriter.println("<td><a href=\"#\">修改</a> <a href=\"#\">删除</a></td>");
                printWriter.println("</tr>");
            }
            printWriter.println("</table>");
            printWriter.println("</html>");
        } else {
            printWriter.println("<h2>数据库中没有数据查询</h2>");
        }
    }

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

8 Session实战保存验证码

生成验证码的方式有很多种，可以使用随机数的方式实现，也可以使用ValidateCode类来实现（需要导入ValidateCode.jar包）。在这里，我们学习使用ValidateCode类来生成验证码

8.1 创建验证码

package com.cxyzxc.www.controller;

import cn.dsna.util.images.ValidateCode;

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

/**
 * 此Servlet的作用是生成验证码并将生成的验证码存储到session中、发送到页面中显示
 */
@WebServlet(name = "VerificationServlet", value = "/VerificationServlet")
public class VerificationServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置验证码规格
        ValidateCode validateCode = new ValidateCode(200, 20, 4, 10);
        //获取验证码
        String code = validateCode.getCode();
        //将验证码存储在session中
        HttpSession session = request.getSession();
        session.setAttribute("code",code);
        //将验证码输出到客户端
        validateCode.write(response.getOutputStream());
    }

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

8.2 登录页面

<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>管理员登录页面</title>
        <link type="text/css" rel="stylesheet" href="css/login.css"/>
    </head>

    <body>
        <div>
            <form action="LoginMgrController" method="post">
                <p>
                    账号：<input type="text" name="username"/>
                </p>
                <p>
                    密码：<input type="password" name="password"/>
                </p>
                <p>
                    验证码：<input type="text" name="verification"/>
                    <img src="/managerProject02_war_exploded/VerificationServlet" />
                </p>
                <p>
                    <input type="submit" value="登录"/>
                </p>
            </form>
        </div>
    </body>
</html>

8.3 LoginMgrController

package com.cxyzxc.www.controller;

import com.cxyzxc.www.entity.Manager;
import com.cxyzxc.www.service.ManagerService;
import com.cxyzxc.www.service.impl.ManagerServiceImpl;

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(name = "LoginMgrController", value = "/LoginMgrController")
public class LoginMgrController extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1、处理乱码
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

        //2、收参（获取客户端发送过来的请求数据）
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String inputCodde = request.getParameter("verification");

        //获取session中的验证码
        HttpSession session = request.getSession();
        String codes = (String) session.getAttribute("code");

        if (!inputCodde.isEmpty() && inputCodde.equalsIgnoreCase(codes)) {
            //3、调用业务方法
            ManagerService managerService = new ManagerServiceImpl();
            Manager manager = managerService.login(username, password);

            //4、处理结果，根据结果做不同的跳转
            if (manager != null) {//manager不为null，说明账号和密码正确，登录成功
                //将获取的账号和密码信息存储在session中
                HttpSession session2 = request.getSession();
                session2.setAttribute("manager", manager);
                //跳转到显示所有管理员信息的Servlet
                response.sendRedirect("/managerProject02_war_exploded/ShowAllManagerController");
            } else {//manager为null。说明账号或者密码错误，登录失败
                response.sendRedirect("/managerProject02_war_exploded/login.html");
            }
        } else {//验证码不对，重新登录
            response.sendRedirect("/managerProject02_war_exploded/login.html");
        }


    }

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

8.4 ShowAllManagerController

package com.cxyzxc.www.controller;

import com.cxyzxc.www.entity.Manager;
import com.cxyzxc.www.service.ManagerService;
import com.cxyzxc.www.service.impl.ManagerServiceImpl;

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.util.List;

@WebServlet(name = "ShowAllManagerController", value = "/ShowAllManagerController")
public class ShowAllManagerController extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //通过HttpSession完成权限控制
        HttpSession session =request.getSession();
        //获取session中存储的值
        Manager manager = (Manager)session.getAttribute("manager");
        //判断获取的值
        if(manager!=null){
            //调用业务,只做业务，业务与显示分离
            ManagerService managerService = new ManagerServiceImpl();
            List<Manager> managers =managerService.showAllManager();
            //将获取的数据存储在request作用域中
            request.setAttribute("managers",managers);
            //转发，跳转到显示结果的Servlet
            request.getRequestDispatcher("/ShowAllManagerJsp").forward(request,response);
        }else{
            //说明没有登录，要先去登录才能进行显示
            response.sendRedirect("/managerProject02_war_exploded/login.html");
        }
    }

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

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