简单的学生管理系统（适合新手理解学习）

时间 2019-11-11

标签简单学生管理系统适合新手理解学习繁體版

原文原文链接

首先看一下学生管理系统的体系（我这个系统作的比较简单）主要应用到了 MVC模式 JDBC 前端用到了 HTML5 CSS JS等html

后台数据处理主要分为：controller层 repository层和service层下面将每一层的代码进行展现->>>前端

首先在entity包内进行类的建立这个系统只实现了对学生的 CRUD（增删改查）因此只须要建立一个学生类（Student）：java

package com.xcl.entity;

public class Student {
    private  Integer id;
    private  String name;
    private  String password;
    private  Double money;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Double getMoney() {
        return money;
    }

    public void setMoney(Double money) {
        this.money = money;
    }

    public Student(Integer id, String name, String password, Double money) {
        this.id = id;
        this.name = name;
        this.password = password;
        this.money = money;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", password='" + password + '\'' +
                ", money=" + money +
                '}';
    }
}

学生类写完以后因为这个系统简单不须要进行业务逻辑处理因此我选择去写 service层 mysql

首先写一个接口在接口中定义 CRUD 的方法：
sql

package com.xcl.service;

import com.xcl.entity.Student;

import java.util.List;

public interface StudentService {
    public List<Student> findAll();
    public void deleteById(Integer id);
    public void update(Integer id,String name,String password,Double money);
    public Student findById(Integer id);
    public void add(String name,String password,Double money);
}

再写一个接口的实现类实现接口中的 CRUD 方法：数据库

package com.xcl.service.impl;

import com.xcl.entity.Student;
import com.xcl.repository.StudentRepository;
import com.xcl.repository.impl.StudentRepositoryImpl;
import com.xcl.service.StudentService;

import java.util.List;

public class StudentServiceImpl implements StudentService {

    private StudentRepository studentRepository = new StudentRepositoryImpl();

    @Override
    public List<Student> findAll() {
        return studentRepository.findAll();
    }

    @Override
    public void deleteById(Integer id) {
        studentRepository.deleteById(id);
    }

    @Override
    public void update(Integer id, String name, String password, Double money) {
        studentRepository.update(id, name, password, money);
    }

    @Override
    public Student findById(Integer id) {
         return studentRepository.findById(id);
    }

    @Override
    public void add(String name, String password, Double money) {
        studentRepository.add(name, password, money);
    }
}

写到这里service层就算是写完了后端

下面咱们进行 repository 和数据库操做方面的代码编写这里会用到 JDBC 数据库链接因此提早写一个 JDBC 链接数据库的工具类：jsp

package com.xcl.Tools;

import java.sql.*;

public class JDBCTools {
    public static Connection getConnection(){
        Connection connection = null;
        try {
            //1.加载驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            //2.获取链接
            String url = "jdbc:mysql://localhost:3306/user?serverTimezone=UTC";
            String user = "root";
            String password = "root";
            connection = DriverManager.getConnection(url,user,password);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }

    public static void release(Connection connection, Statement statement, ResultSet resultSet){
        try {
            if(connection!=null){
                connection.close();
            }
            if(statement!=null){
                statement.close();
            }
            if(resultSet!=null){
                resultSet.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

下面是 repository 层代码的编写仍是老样子先写一个接口接口里面写好须要实现的 CRUD 方法：ide

package com.xcl.repository;

import com.xcl.entity.Student;

import java.util.List;

public interface StudentRepository {
    public List<Student> findAll();
    public void deleteById(Integer id);
    public void update(Integer id,String name,String password,Double money);
    public Student findById(Integer id);
    public void add(String name,String password,Double money);
}

再写一个实现类实现接口里面定义的方法：工具

package com.xcl.repository.impl;

import com.xcl.Tools.JDBCTools;
import com.xcl.entity.Student;
import com.xcl.repository.StudentRepository;


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

public class StudentRepositoryImpl implements StudentRepository {
    /**
     * 查询
     *
     * @return
     */
    @Override
    public List<Student> findAll() {
        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;
        List<Student> list = new ArrayList<>();
        try {
            connection = JDBCTools.getConnection();
            String sql = "select * from stu";
            statement = connection.prepareStatement(sql);
            resultSet = statement.executeQuery();
            Student student = null;
            while (resultSet.next()) {
                int id = resultSet.getInt(1);
                String name = resultSet.getString(2);
                String password = resultSet.getString(3);
                Double money = resultSet.getDouble(4);
                student = new Student(id, name, password, money);
                list.add(student);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCTools.release(connection, statement, resultSet);
        }
        return list;
    }

    /**
     *
     * 删除
     *
     * @param id
     */
    @Override
    public void deleteById(Integer id) {
        Connection connection = null;
        PreparedStatement statement = null;
        try {
            connection = JDBCTools.getConnection();
            String sql = "delete from stu where id = ?";
            statement = connection.prepareStatement(sql);
            statement.setInt(1, id);
            statement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCTools.release(connection, statement, null);
        }
    }

    /**
     *
     * 修改
     *
     * @param id
     * @param name
     * @param password
     * @param money
     */
    @Override
    public void update(Integer id, String name, String password, Double money) {
        Connection connection = null;
        PreparedStatement statement = null;
        try {
            connection = JDBCTools.getConnection();
            String sql = "update stu set name =?,password=?,money=? where id=?";
            statement = connection.prepareStatement(sql);
            statement.setString(1, name);
            statement.setString(2, password);
            statement.setDouble(3, money);
            statement.setInt(4, id);
            statement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCTools.release(connection, statement, null);
        }
    }

    /**
     * @param id
     * @return
     */
    @Override
    public Student findById(Integer id) {
        Connection connection = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;
        Student student = null;
        try {
            connection = JDBCTools.getConnection();
            String sql = "select * from stu where id=?";
            statement = connection.prepareStatement(sql);
            System.out.println(sql);
            statement.setInt(1, id);
            resultSet = statement.executeQuery();
            if (resultSet.next()) {
                id = resultSet.getInt(1);
                String name = resultSet.getString(2);
                String password = resultSet.getString(3);
                Double money = resultSet.getDouble(4);
                student = new Student(id, name, password, money);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCTools.release(connection, statement, resultSet);
        }
        return student;
    }

    /**
     * 添加
     *
     *
     * @param name
     * @param password
     * @param money
     */
    @Override
    public void add(String name, String password, Double money) {
        Connection connection = null;
        PreparedStatement statement = null;
        try {
            connection = JDBCTools.getConnection();
            String sql = "insert into stu (name,password,money) values (?,?,?)";
            statement = connection.prepareStatement(sql);
            statement.setString(1, name);
            statement.setString(2, password);
            statement.setDouble(3, money);
            statement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JDBCTools.release(connection, statement, null);
        }
    }
}

接下来就是要编写先后端交互的代码也就是 controller 层的编写

package com.xcl.controller;

import com.xcl.service.StudentService;
import com.xcl.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;

@WebServlet("/student")
public class StudentServlet extends HttpServlet {

    private StudentService studentService = new StudentServiceImpl();
    private final static String USERNAME = "admin";
    private final static String PASSWORD = "123";


    @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 {
        req.setCharacterEncoding("UTF-8");
        String method = req.getParameter("method");
        if (method == null) method = "findAll";
        switch (method) {
            case "findAll":
                req.setAttribute("list", studentService.findAll());
                req.getRequestDispatcher("index.jsp").forward(req, resp);
                break;
            case "deleteById":
                String idStr = req.getParameter("id");
                Integer id = Integer.parseInt(idStr);
                studentService.deleteById(id);
                resp.sendRedirect("/student");
                break;
            case "findById":
                idStr = req.getParameter("id");
                id = Integer.parseInt(idStr);
                req.setAttribute("student", studentService.findById(id));
                req.getRequestDispatcher("update.jsp").forward(req, resp);
                break;
            case "add":
                String name = req.getParameter("name");
                String password = req.getParameter("password");
                String money1 = req.getParameter("money");
                Double money = Double.parseDouble(money1);
                studentService.add( name, password, money);
                resp.sendRedirect("/student");
                break;
            case "update":
                idStr = req.getParameter("id");
                id = Integer.parseInt(idStr);
                name = req.getParameter("name");
                password = req.getParameter("password");
                money1 = req.getParameter("money");
                money = Double.parseDouble(money1);
                studentService.update(id, name, password, money);
                resp.sendRedirect("/student");
                break;
            case "login":
                String username = req.getParameter("username");
                password = req.getParameter("password");
                if (username.equals(USERNAME) && password.equals(PASSWORD)) {
                    req.getSession().setAttribute("name", username);
                    resp.sendRedirect("/student");
                } else {
                    req.getRequestDispatcher("index.html").forward(req, resp);
                }
                break;
            case "logout":
                req.getSession().invalidate();
                req.getRequestDispatcher("index.html").forward(req, resp);
                break;
        }

    }
}