elementui的介绍和使用以及使用elementui完成增删改查和登录-CRMEB社区

1. 正文

1、elementui布局框架
2、使用elementui+vue+axios完成一个案例。

2.elementui布局框架

Element，一套为开发者、设计师和产品经理准备的基于 Vue 2.0 的桌面端组件库。

换句话说:Element它是再vue2.0得基础上，提供了各种组件(比如表单表格菜单导航.....),使用这些组件可以更好得完成功能和布局。

这些组件我们使用谁我们就讲谁，你们要主要看看我是如何使用这些组件得，那么你再使用其他组件时也可以按照这种方式来用。

2.1如何使用elementui组件

（1）需要再相应得网页中引入vue和elementui得文件

注意:==必须先引入vue在引入element==

 <!--引入element得css样式-->
    <link type="text/css" rel="stylesheet" href="css/index.css"/>
    <!--引入vue得js文件 这个必须在element之前引入-->
    <script type="text/javascript" src="js/vue.js"></script>
    <!--element得js文件-->
    <script type="text/javascript" src="js/index.js"></script>

(2)设置表格组件

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <!--引入element得css样式-->
    <link type="text/css" rel="stylesheet" href="css/index.css"/>
    <!--引入vue得js文件 这个必须在element之前引入-->
    <script type="text/javascript" src="js/vue.js"></script>
    <!--element得js文件-->
    <script type="text/javascript" src="js/index.js"></script>
</head>
<body>
   <!--创建一个标签使vue挂载到该标签上-->
   <div id="app">
       <!--:data==绑定了vue中定义得数据tableData
           border表示设置表格边框
           el-table-column:表示列标签
              prop:该属性得名称必须和tableData中对象得属性名一致。
              label：表格得标题
              width: 设置列得宽度
       -->
       <el-table
               :data="tableData"
               border
               style="width: 100%">
           <el-table-column
                   prop="date"
                   label="日期"
                   >
           </el-table-column>
           <el-table-column
                   prop="name"
                   label="姓名"
                   >
           </el-table-column>
           <el-table-column
                   prop="address"
                   label="地址">
           </el-table-column>
           <el-table-column
                   fixed="right"
                   label="操作"
                   >
               <template slot-scope="scope">
                   <el-button type="text" size="small">查看</el-button>
                   <el-button type="text" size="small">编辑</el-button>
               </template>
       </el-table>
   </div>
</body>
<!--表示自定义得js文件-->
<script>
      var app=new Vue({
           el:"#app",
           data:{
                tableData:[
                    {"date":"2020-05-11","name":"张三","address":"北京"},
                    {"date":"2021-05-11","name":"李四","address":"郑州"},
                    {"date":"2022-05-11","name":"五五","address":"杭州"},
                    {"date":"2023-06-11","name":"六六","address":"上海"},
                ],
           }
      })
</script>
</html>

把上面得操作文字换成按钮形式:

<el-table-column
                   fixed="right"
                   label="操作"
                   >
     <template slot-scope="scope">
         <el-button type="success" size="small" icon="el-icon-edit" plain>编辑</el-button>
         <el-button type="danger"  size="small" icon="el-icon-delete" plain>删除</el-button>
     </template>
</el-table-column>

浏览器并没有显示图标得样式:我们需要引入下面三个文件到工程中

3. elementui+axios+后台代码

我们上面的表格数据都是死数据。而我们实际开发中表格数据应该从后台数据库中查询获取的。

-- 创建数据库
create database vue01;
-- 切换数据库到vue01
use vue01;
-- 创建表
create table t_dept(
     dept_id int primary key auto_increment COMMENT '部门号',
		 dept_name varchar(20) COMMENT '部门名称',
		 loc varchar(20) COMMENT '部门所在地'
);
create table t_emp(
    emp_id int primary key auto_increment COMMENT '员工编号',
		emp_name varchar(20) COMMENT '员工姓名',
		emp_sex TINYINT COMMENT '性别 0表示男 1表示女',
		emp_age int  COMMENT '年龄',
		emp_salary DECIMAL(7,2) COMMENT '工资',
		dept_id int COMMENT '关联的部门号'
);
-- 添加数据
insert into t_dept values
(null,'研发部','郑州'),(null,'市场部','杭州'),(null,'人事部','北京')
 
insert into t_emp values 
(null,'张三',0,25,1666.65,1),
(null,'李四',1,26,2555.65,2),
(null,'王五',0,32,6666.65,3),
(null,'赵六',0,36,8888.65,1)

(2)创建员工实体类

package com.aaa.entity;
 
/**
 * @program: vue01-qy151
 * @description: 员工表的实体类
 * @author: ysh
 * @create: 2022-05-26 15:21
 **/
public class Emp {
    //员工编号
    private int empId;
    //员工姓名
    private String empName;
    //性别
    private int empSex;
    //年龄
    private int empAge;
    //薪水
    private Double empSalary;
    //部门号
    private int deptId;
 
    public int getEmpId() {
        return empId;
    }
 
    public void setEmpId(int empId) {
        this.empId = empId;
    }
 
    public String getEmpName() {
        return empName;
    }
 
    public void setEmpName(String empName) {
        this.empName = empName;
    }
 
    public int getEmpSex() {
        return empSex;
    }
 
    public void setEmpSex(int empSex) {
        this.empSex = empSex;
    }
 
    public int getEmpAge() {
        return empAge;
    }
 
    public void setEmpAge(int empAge) {
        this.empAge = empAge;
    }
 
    public Double getEmpSalary() {
        return empSalary;
    }
 
    public void setEmpSalary(Double empSalary) {
        this.empSalary = empSalary;
    }
 
    public int getDeptId() {
        return deptId;
    }
 
    public void setDeptId(int deptId) {
        this.deptId = deptId;
    }
}

(3)员工的dao

/**
     * 查询所有员工信息
     * @return 所有员工信息
     */
    public List<Emp> findAll(){
        List<Emp> list = new ArrayList<>();
        try {
            getConn();
            String sql="select * from t_emp";
            ps=connection.prepareStatement(sql);
            rs=ps.executeQuery();
            while(rs.next()){
                 Emp emp=new Emp();
                 emp.setEmpId(rs.getInt("emp_id"));
                 emp.setEmpName(rs.getString("emp_name"));
                 emp.setEmpAge(rs.getInt("emp_age"));
                 emp.setEmpSalary(rs.getDouble("emp_salary"));
                 emp.setEmpSex(rs.getInt("emp_sex"));
                 emp.setDeptId(rs.getInt("dept_id"));
                 list.add(emp);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            closeAll();
        }
        return list;
    }

(4)测试dao方法

package com.aaa.test;
 
import com.aaa.dao.EmpDao;
import org.junit.Test;
 
/**
 * @program: vue01-qy151
 * @description:
 * @author: ysh
 * @create: 2022-05-26 15:30
 **/
public class TestEmpDao {
    private EmpDao empDao=new EmpDao();
    @Test
    public void testFindAll(){
        System.out.println(empDao.findAll());
    }
}

(5)controller

package com.aaa.controller;
 
import com.aaa.dao.EmpDao;
import com.aaa.entity.Emp;
import com.alibaba.fastjson.JSON;
 
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.io.IOException;
import java.io.PrintWriter;
import java.util.List;
 
@WebServlet(name = "EmpServlet",urlPatterns = "/EmpServlet")
public class EmpServlet extends HttpServlet {
    private EmpDao empDao=new EmpDao();
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         req.setCharacterEncoding("utf-8");
         resp.setContentType("text/html;charset=utf-8");
         //接受处理的标识
         String method = req.getParameter("method");
         if("delete".equals(method)){
 
         }else{
             //查询所有的操作
             queryAll(req,resp);
         }
    }
 
    private void queryAll(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {
        List<Emp> list = empDao.findAll();
        //把java集合转换为json对象。---fastjson
        String result = JSON.toJSONString(list);
        PrintWriter writer = resp.getWriter();
        //输出给客户
        writer.print(result);
        //关闭资源
        writer.flush();
        writer.close();
    }
}

(6)展示到网页

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <!--引入element得css样式-->
    <link type="text/css" rel="stylesheet" href="css/index.css"/>
    <!--引入vue得js文件 这个必须在element之前引入-->
    <script type="text/javascript" src="js/vue.js"></script>
    <script type="text/javascript" src="js/axios.min.js"></script>
    <!--element得js文件-->
    <script type="text/javascript" src="js/index.js"></script>
</head>
<body>
   <!--创建一个标签使vue挂载到该标签上-->
   <div id="app">
       <!--:data==绑定了vue中定义得数据tableData
           border表示设置表格边框
           el-table-column:表示列标签
              prop:该属性得名称必须和tableData中对象得属性名一致。
              label：表格得标题
              width: 设置列得宽度
       -->
       <el-table
               :data="tableData"
               border
               style="width: 100%">
           <el-table-column
                   prop="empId"
                   label="员工编号"
                   >
           </el-table-column>
           <el-table-column
                   prop="empName"
                   label="员工姓名"
                   >
           </el-table-column>
           <el-table-column
                   prop="empSex"
                   label="性别">
           </el-table-column>
           <el-table-column
                   prop="empAge"
                   label="年龄">
           </el-table-column>
           <el-table-column
                   prop="empSalary"
                   label="薪水">
           </el-table-column>
           <el-table-column
                   prop="deptId"
                   label="部门编号">
           </el-table-column>
           <el-table-column
                   fixed="right"
                   label="操作"
                   >
               <template slot-scope="scope">
                   <el-button type="success" size="small" icon="el-icon-edit" plain>编辑</el-button>
                   <el-button type="danger"  size="small" icon="el-icon-delete" plain>删除</el-button>
               </template>
           </el-table-column>
       </el-table>
   </div>
</body>
<!--表示自定义得js文件-->
<script>
      var app=new Vue({
           el:"#app",
           data:{
                tableData:[],
           },
           //页面加载完毕后执行；
           created(){
               this.initTable();
           },
           methods:{
               //初始化表格数据
               initTable(){
                    var that=this;
                    //通过axios后台服务发送异步请求
                    axios.post("EmpServlet").then(function(result){
                          if(result.data.code===2000){//===:比较值和引用是否相同
                              that.tableData=result.data.data;
                          }else{
 
                          }
                    })
               }
           }
      })
</script>
</html>

我们发现上面的性别显示的为数字如何显示男和女呢我们需要自定义列

<el-table-column
                   prop="empSex"
                   label="性别">
               <template slot-scope="scope">
                   <el-tag size="medium"> {{ scope.row.empSex==0?"男":"女" }}</el-tag>
               </template>
           </el-table-column>

4.删除

(1)前端

  var qs=Qs;               axios.post("EmpServlet",qs.stringify({"method":"delete","id":id})).then(function(result){
          that.initTable();
 })

axios底层post提交的参数会封装到request playload请求载体中，使用request.getParamter是无法接受到请求载体的参数， request.getParamter它只能接受query param参数和form data参数。我们可以借助qs把请求载体的参数转换为form data参数。转换的步骤

(1) 在网页中引入qs
    <script type="text/javascript" src="js/qs.min.js"></script>
(2) 把Qs对象重写赋值一个参数
    var qs=Qs;
(3) 把  request playload使用 stringify方法转换
qs.stringify({"":"","":""})

（2）servlet

private void delete(HttpServletRequest req, HttpServletResponse resp)  throws ServletException, IOException{
        String id = req.getParameter("id");
        int row=empDao.delete(id);
        PrintWriter writer = resp.getWriter();
        if(row==1){ //删除成功
            CommonResult commonResult=new CommonResult(2000,"删除成功",null);
            writer.print(JSON.toJSONString(commonResult));
        }else{ //删除失败
            CommonResult commonResult=new CommonResult(5000,"删除失败",null);
            writer.print(JSON.toJSONString(commonResult));
        }
        writer.flush();
        writer.close();
    }

(3) dao

   //删除操作
    public int delete(String id) {
        String  sql ="delete from t_emp where emp_id=?";
        return edit(sql,id);
    }

5.添加功能

点击添加按钮显示一个弹出层

 <el-dialog
            title="添加员工"
            :visible.sync="addDialogVisible"
            width="30%"
           >
        <!--:model==绑定表单数据-->
        <el-form :model="addform">
            <el-form-item label="姓名" label-width="40px">
                <el-input v-model="addform.empName" autocomplete="off"></el-input>
            </el-form-item>
            <el-form-item label="性别" label-width="40px">
                <el-radio v-model="addform.empSex" :label="0">男</el-radio>
                <el-radio v-model="addform.empSex" :label="1">女</el-radio>
            </el-form-item>
            <el-form-item label="年龄" label-width="40px">
                <el-input v-model="addform.empAge" autocomplete="off"></el-input>
            </el-form-item>
            <el-form-item label="薪水" label-width="40px">
                <el-input v-model="addform.empSalary" autocomplete="off"></el-input>
            </el-form-item>
        </el-form>
        <span slot="footer" class="dialog-footer">
            <el-button @click="addDialogVisible = false">取 消</el-button>
            <el-button type="primary" @click="">确 定</el-button>
        </span>
    </el-dialog>

(2)添加点击事件

 //添加的点击事件
            addEmp(){
                 var qs=Qs;
                 var that=this;
                 axios.post("EmpServlet?method=insert",qs.stringify(this.addform)).then(function(result){
                         if(result.data.code===2000){
                               that.$message.success(result.data.msg);
                               that.initTable();//重新加载表格
                               that.addDialogVisible=false;
                         }
                 })
            }

(3)添加servlet

//添加
    private void insert(HttpServletRequest req, HttpServletResponse resp)  throws ServletException, IOException{
        String name = req.getParameter("empName");
        String sex = req.getParameter("empSex");
        String age = req.getParameter("empAge");
        String salary = req.getParameter("empSalary");
        Emp emp = new Emp(name,Integer.parseInt(sex),Integer.parseInt(age),Double.parseDouble(salary));
        int row=empDao.add(emp);
        PrintWriter writer = resp.getWriter();
        if(row==1){ //添加成功
            CommonResult commonResult=new CommonResult(2000,"添加成功",null);
            writer.print(JSON.toJSONString(commonResult));
        }else{ //添加失败
            CommonResult commonResult=new CommonResult(5000,"添加失败",null);
            writer.print(JSON.toJSONString(commonResult));
        }
        writer.flush();
        writer.close();
    }

(4)dao的代码

 /**
     * 添加功能
     * @param emp
     * @return
     */
    public int add(Emp emp) {
        String sql="insert into t_emp(emp_name,emp_sex,emp_age,emp_salary) values(?,?,?,?)";
        return edit(sql,emp.getEmpName(),emp.getEmpSex(),emp.getEmpAge(),emp.getEmpSalary());
    }

6.修改功能

（1）点击编辑回显数据

<!--修改员工的对话框-->
    <el-dialog
            title="修改员工"
            :visible.sync="editDialogVisible"
            width="30%"
    >
        <!--:model==绑定表单数据-->
        <el-form :model="editform" :rules="addRules" ref="addRuleForm">
            <el-form-item label="姓名" label-width="80px" prop="empName">
                <el-input v-model="editform.empName" autocomplete="off"></el-input>
            </el-form-item>
            <el-form-item label="性别" label-width="80px">
                <el-radio v-model="editform.empSex" :label="0">男</el-radio>
                <el-radio v-model="editform.empSex" :label="1">女</el-radio>
            </el-form-item>
            <el-form-item label="年龄" label-width="80px" prop="empAge">
                <el-input v-model.number="editform.empAge" autocomplete="off"></el-input>
            </el-form-item>
            <el-form-item label="薪水" label-width="80px">
                <el-input v-model="editform.empSalary" autocomplete="off"></el-input>
            </el-form-item>
        </el-form>
        <span slot="footer" class="dialog-footer">
            <el-button @click="editDialogVisible = false">取 消</el-button>
            <el-button type="primary" @click="editEmp">确定修改</el-button>
        </span>
    </el-dialog>

注意: ==:visible.sync="editDialogVisible" 一定要在vue data中定义editDialogVisible :model="editform" 保证在vue data中定义editform==

<el-button @click="edit(scope.row)" type="success" size="small" icon="el-icon-edit" plain>编辑</el-button>
 
  //修改按钮点击事件
            edit(row){
                  //1.显示修改弹出层
                  this.editDialogVisible=true;
                  //2.数据回显
                  this.editform=row;
            },

(2) 点击确认修改按钮

<el-button type="primary" @click="editEmp">确定修改</el-button>

//确认修改
editEmp(){
    var that=this;
    var qs=Qs;
    this.$refs['editRuleForm'].validate((valid) => {
        if (valid) { //表单校验通过
            axios.post("EmpServlet?method=edit",qs.stringify(this.editform)).then(function(result){
                if(result.data.code===2000){
                    that.$message.success(result.data.msg);//弹出成功的消息
                    that.editDialogVisible=false; //隐藏修改对话框
                    that.initTable(); //重新加载表格数据
                }
            })
        }
    });
},

servlet:

//修改操作
    private void edit(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException{
        String name = req.getParameter("empName");
        String sex = req.getParameter("empSex");
        String age = req.getParameter("empAge");
        String salary = req.getParameter("empSalary");
        String  id = req.getParameter("empId");
        Emp emp = new Emp(Integer.parseInt(id),name,Integer.parseInt(sex),Integer.parseInt(age),Double.parseDouble(salary));
        int row=empDao.update(emp);
        PrintWriter writer = resp.getWriter();
        if(row==1){ //删除成功
            CommonResult commonResult=new CommonResult(2000,"修改成功",null);
            writer.print(JSON.toJSONString(commonResult));
        }else{ //删除失败
            CommonResult commonResult=new CommonResult(5000,"修改失败",null);
            writer.print(JSON.toJSONString(commonResult));
        }
        writer.flush();
        writer.close();
    }

dao:

/**
     * 修改功能
     * @param emp
     * @return
     */
    public int update(Emp emp) {
        String sql = "update t_emp set emp_name=?,emp_sex=?,emp_age=?,emp_salary=? where emp_id=?";
        return edit(sql,emp.getEmpName(),emp.getEmpSex(),emp.getEmpAge(),emp.getEmpSalary(),emp.getEmpId());
    }

7.登录

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>登录页面</title>
    <!--引入element得css样式-->
    <link type="text/css" rel="stylesheet" href="css/index.css"/>
    <!--引入vue得js文件 这个必须在element之前引入-->
    <script type="text/javascript" src="js/vue.js"></script>
    <script type="text/javascript" src="js/qs.min.js"></script>
    <script type="text/javascript" src="js/axios.min.js"></script>
    <!--element得js文件-->
    <script type="text/javascript" src="js/index.js"></script>
    <style>
        /*body{
            background: url("imgs/1.webp") no-repeat;
        }*/
         body,.box{
             overflow: hidden;
             height: 100%;
         }
        .box{
             background: url("imgs/1.webp") no-repeat;
        }
        #loginBox {
            width: 450px;
            height: 300px;
            background: white;
            border-radius: 3px;
            position: absolute;
            left: 50%;
            top: 50%;
            transform: translate(-50%, -50%);
        }
       #loginBox>.avatar_box{
            height: 130px;
            width: 130px;
            border: 1px solid #eee;
            border-radius: 50%;
            padding: 10px;
            box-shadow: 0 0 10px #ddd;
            position: absolute;
            left: 50%;
            transform: translate(-50%, -50%);
            background-color: #fff;
        }
         #loginBox>.avatar_box>img {
             width: 100%;
             height: 100%;
             border-radius: 50%;
             background-color: #eee;
         }
         .login_form {
             position: absolute;
             bottom: 0;
             width: 100%;
             padding: 0 20px;
             box-sizing: border-box;
         }
    </style>
</head>
<body background="imgs/3.webp">
<div class="box">
    <div id="loginBox">
        <!-- 头像 -->
        <div class="avatar_box">
             <img src="imgs/1.jpg" />
        </div>
        <el-form label-width="80px" :model="loginForm" :rules="rules" ref="loginFormRef" class="login_form">
            <el-form-item label="账号:" prop="username">
                <el-input v-model="loginForm.username"></el-input>
            </el-form-item>
            <el-form-item label="密码:" prop="password">
                <el-input v-model="loginForm.password"></el-input>
            </el-form-item>
            <el-form-item>
                <el-button type="primary" @click="submitForm()">登录</el-button>
            </el-form-item>
        </el-form>
    </div>
</div>
 
<script>
    var app = new Vue({
        el: ".box",
        data: {
            loginForm: {},
            //校验规则
            rules: {
                username: [
                    {required: true, message: "请输入账号", trigger: "blur"},
                    {min: 5, max: 12, message: "账号的长度必须{5~12}", trigger: "blur"},
                ],
                password: [
                    {required: true, message: "请输入密码", trigger: "blur"},
                    {min: 6, max: 12, message: "密码的长度必须{6~12}", trigger: "blur"},
                ]
            }
        },
        methods: {
            submitForm() {
                var that = this;
                var qs = Qs;
                this.$refs['loginFormRef'].validate((valid) => {
                    if (valid) {
                        axios.post("UserServlet?method=login", qs.stringify(this.loginForm)).then(function (result) {
                            if (result.data.code === 2000) {
                                that.$message.success(result.data.msg);
                                location.href = "element01.html"
                            } else {
                                that.$message.error(result.data.msg);
                            }
                        });
                    }
                })
            }
        }
    })
</script>
</body>
</html>

(2)servlet

 private void login(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {
        PrintWriter writer = resp.getWriter();
        String username = req.getParameter("username");
        String password = req.getParameter("password");
 
        if("admin".equals(username)&&"123456".equals(password)){
            HttpSession session = req.getSession();
            session.setAttribute("username",username);
            CommonResult commonResult=new CommonResult(2000,"登录成功",null);
            writer.print(JSON.toJSONString(commonResult));
        }else{
            CommonResult commonResult=new CommonResult(5000,"账号或密码错误",null);
            writer.print(JSON.toJSONString(commonResult));
        }
        writer.flush();
        writer.close();
    }

8.表单校验

Form 组件提供了表单验证的功能，只需要通过 rules 属性传入约定的验证规则，并将 Form-Item 的 prop 属性设置为需校验的字段名即可

如果不符合表单的校验应该不允许表单提交

//添加的点击事件
            addEmp(){
                this.$refs['addRuleForm'].validate((valid) => {
                    if (valid) { //表单校验通过
                        var qs=Qs;
                        var that=this;
                        axios.post("EmpServlet?method=insert",qs.stringify(this.addform)).then(function(result){
                            if(result.data.code===2000){
                                that.$message.success(result.data.msg);
                                that.initTable();//重新加载表格
                                that.addDialogVisible=false; //隐藏弹出层
                            }
                        })
                    }
                });
 
            }

9.添加登录过滤器

package com.qy151.filter;
 
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
 
/**
 * @unthor : YSH
 * @date : 13:44 2022/5/29
 */
@WebFilter(filterName = "UserFilter",urlPatterns = "/*")
public class UserFilter implements Filter {
 
    public void init(FilterConfig filterConfig) throws ServletException {
 
    }
 
 
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request= (HttpServletRequest) servletRequest;
        HttpServletResponse response= (HttpServletResponse) servletResponse;
        //1.接受请求路径
        String path = request.getRequestURI();
        //2.设置放行的路径
        if(path.contains("login.html")
                ||path.contains("UserServlet")
                ||path.endsWith(".js")
                ||path.endsWith(".css")
                ||path.endsWith(".jpg")
                ||path.endsWith(".gif")
                ||path.endsWith(".jpeg")
                ||path.endsWith(".webp")
                ||path.endsWith(".png")){
            filterChain.doFilter(request,response);
            return;
        }
        //3.判断用户是否登录
        Object username = request.getSession().getAttribute("username");
        if(username!=null){
            filterChain.doFilter(request,response);
            return;
        }
 
        //4.跳转到登录页面
        response.sendRedirect("login.html");
 
    }
 
 
    public void destroy() {
 
    }
}