Session详解，学习 Session对象一篇文章就够了

ゝ一纸荒年。 2024-03-27 17:34 36阅读 0赞

**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

--------------------

### 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);
        }
    }

![7ebb4c72d9d04aad82ca1f4c1a3875c7.png][]

#### 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);
        }
    }

![230a336830cd41baa52da8b358601c15.png][]

#### 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);
        }
    }

![599732cd800f4299bf3ee9635b42d9f6.png][]

### 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 ####

![e932dc58c09443b98730d1969bb76df8.png][]

### 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);
        }
    }

![b135945017ef4d428327363c70490d96.png][]

#### 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);
        }
    }

![ea9d6389b7a34361805a0a74fdb61230.png][]

### .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

![b451319f8b014035919a7165544db19c.png][]

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

![8ab33fb4844b4b67b406b5806cd1eff3.png][]

#### 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);
        }
    }

![f932f75605034c6ca3e03d044c634cdc.png][]

### 7 Session实战权限验证 ###

![3713e81ff9544c8590fbc805cea05eed.png][]

#### 7.1 创建管理员表manager并添加数据 ####

![ef61d74dd3cf466b926954d982d2628a.png][]

#### 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);
        }
    }

#### 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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