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

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

                                                                        
                    账号：                
                
                    密码：                
                
                                    
                        

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 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 managers = (List) request.getAttribute("managers");        //获取输出流        PrintWriter printWriter = response.getWriter();        if (managers.size() != 0) {            printWriter.println("");            printWriter.println("");            printWriter.println("");            printWriter.println("");            printWriter.println("");            printWriter.println("");            printWriter.println("");            printWriter.println(" ");            printWriter.println(" ");            printWriter.println(" ");            printWriter.println(" ");            printWriter.println(" ");            for (int i = 0; i < managers.size(); i++) {                printWriter.println("");                printWriter.println("");                printWriter.println("");                printWriter.println("");                printWriter.println("");                printWriter.println("");            }            printWriter.println("
序号
账号
密码
操作
" + (i + 1) + "
" + managers.get(i).getUsername() + "
" + managers.get(i).getPassword() + "
修改 删除
");            printWriter.println("");        } else {            printWriter.println("
数据库中没有数据查询
");        }    }    @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

                                                                        
                    账号：                
                
                    密码：                
                
                    验证码：                                    
                
                                    
                        

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 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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