详细：MVC开发模式（代码示例）

代码布局：

 Student.java

package com.zzk.bean;

/**
 * @Author: zzk
 * @Description: 实体类包-主要存放和数据库对应的实体类---类名=表名;列名=属性名
 *               实体类需要包含：属性，构造方法(无参，全参构造)，setter/getter方法
 *               属于Model
 * @Date Created in 2021-03-25-23:44
 * @Modified By:
 */
public class Student {
    private Integer stuid;
    private String stuname;
    private Integer age;
    private Integer sex;

    public Student() {}

    public Student(Integer stuid, String stuname, Integer age, Integer sex) {
        this.stuid = stuid;
        this.stuname = stuname;
        this.age = age;
        this.sex = sex;
    }

    public Integer getStuid() {
        return stuid;
    }

    public void setStuid(Integer stuid) {
        this.stuid = stuid;
    }

    public String getStuname() {
        return stuname;
    }

    public void setStuname(String stuname) {
        this.stuname = stuname;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Integer getSex() {
        return sex;
    }

    public void setSex(Integer sex) {
        this.sex = sex;
    }
}

StudentDao.java

package com.zzk.dao;

import com.zzk.bean.Student;

import java.util.List;

/**
 * @Author: zzk
 * @Description: 命名：实体类名+Dao
 *
 * @Date Created in 2021-03-25-23:51
 * @Modified By:
 */
public interface StudentDao {
    //定义操作数据库的方法
    List<Student> getAll();
}

StudentDaoImpl.java

package com.zzk.dao.impl;

import com.zzk.bean.Student;
import com.zzk.dao.StudentDao;
import com.zzk.util.DruidUtil;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

/**
 * @Author: zzk
 * @Description: 命名：接口名+Impl
 * @Date Created in 2021-03-25-23:56
 * @Modified By:
 */
public class StudentDaoImpl extends DruidUtil implements StudentDao {
    @Override
    public List<Student> getAll() {
        List list = new ArrayList();
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            connection = getConnection();
            preparedStatement = connection.prepareStatement("select * from student");
            resultSet = preparedStatement.executeQuery();
            while (resultSet.next()){
                Student student = new Student();
                student.setStuid(resultSet.getInt("stuid"));
                student.setStuname(resultSet.getString("stuname"));
                student.setAge(resultSet.getInt("age"));
                student.setSex(resultSet.getInt("sex"));
                list.add(student);
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        } finally {
            close(connection,preparedStatement,resultSet);
        }
        return list;
    }
}

StudentService.java

package com.zzk.service;

import com.zzk.bean.Student;

import java.util.List;

/**
 * @Author: zzk
 * @Description: 命名：实体类名+Service
 *               Service层主要定义业务逻辑，现阶段主要实现调取dao层
 * @Date Created in 2021-03-26-0:18
 * @Modified By:
 */
public interface StudentService {
    //查询全部
    List<Student> getAll();
}

StudentServlet.java

package com.zzk.servlet;

import com.zzk.bean.Student;
import com.zzk.service.StudentService;
import com.zzk.service.impl.StudentServiceImpl;

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.util.List;

/**
 * @Author: zzk
 * @Description: C-controller 控制层
 * @Date Created in 2021-03-26-0:24
 * @Modified By:
 */
@WebServlet(urlPatterns = "/getstus")
public class StudentServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.接收请求参数
        //2.调取service层方法
        StudentService studentService = new StudentServiceImpl();
        List<Student> all = studentService.getAll();
        //3.跳转页面(这里后台传递数据给前台，所以用转发，不用重定向)
        req.setAttribute("allStudent",all);
        req.getRequestDispatcher("show.jsp").forward(req,resp);
    }
}

DruidUtil.java

package com.zzk.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import javax.xml.transform.Result;
import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class DruidUtil {

    private static DataSource ds;
    static{
        try {
            Properties ppt = new Properties();
            ppt.load(DruidUtil.class.getClassLoader().getResourceAsStream("druid.properties"));
            ds = DruidDataSourceFactory.createDataSource(ppt);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }


    /**
     * 从连接池中取出一个连接给用户
     * @return
     */
    public static Connection getConnection(){
        try {
            return ds.getConnection();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return null;
    }


    public static void close(Connection conn, Statement state, ResultSet rs){
        try {
            rs.close();
        } catch (Exception throwables) {
            throwables.printStackTrace();
        }
        try {
            state.close();
        } catch (Exception throwables) {
            throwables.printStackTrace();
        }
        try {
            conn.close();
        } catch (Exception throwables) {
            throwables.printStackTrace();
        }
    }
}

druid.properties

url=jdbc:mysql://localhost:3306/mymvc?useUnicode=true&characterEncoding=utf-8&serverTimezone=UTC&useSSL=false
username=root
password=123456
driverClassName=com.mysql.cj.jdbc.Driver
initialSize=5
maxActive=10
minIdle=5
maxWait=3000

index.jsp

<%--
  Created by IntelliJ IDEA.
  User: lenovo
  Date: 2021/3/25
  Time: 23:30
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  <a href="getstus">查询学生列表</a>
  </body>
</html>

show.jsp

<%--
  Created by IntelliJ IDEA.
  User: lenovo
  Date: 2021/3/26
  Time: 0:36
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>学生信息</title>
</head>
<body>
    <div align="center">
        <h1>全体学生信息</h1>
    </div>
    <div align="center">
        <table border="1" width="500px" bgcolor="aqua">
            <tr>
                <th>学生ID</th>
                <th>学生姓名</th>
                <th>学生年龄</th>
                <th>学生性别</th>
            </tr>
            <c:forEach items="${allStudent}" var="stuInfo">
                <tr align="center">
                    <td>${stuInfo.stuid}</td>
                    <td>${stuInfo.stuname}</td>
                    <td>${stuInfo.age}</td>
                    <td>${stuInfo.sex==1?"男":"女"}</td>
                </tr>
            </c:forEach>
        </table>
    </div>
</body>
</html>