簡單的學生管理系統（適合新手理解學習）

時間 2019-11-11

標籤簡單學生管理系統適合新手理解學習简体版

原文原文鏈接

首先看一下學生管理系統的體系（我這個系統作的比較簡單）主要應用到了 MVC模式 JDBC 前端用到了 HTML5 CSS JS等html

後臺數據處理主要分爲：controller層 repository層和service層下面將每一層的代碼進行展現->>>前端

首先在entity包內進行類的建立這個系統只實現了對學生的 CRUD（增刪改查）因此只須要建立一個學生類（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 +
                '}';
    }
}

學生類寫完以後因爲這個系統簡單不須要進行業務邏輯處理因此我選擇去寫 service層 mysql

首先寫一個接口在接口中定義 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);
}

再寫一個接口的實現類實現接口中的 CRUD 方法：數據庫

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);
    }
}

寫到這裏service層就算是寫完了後端

下面咱們進行 repository 和數據庫操做方面的代碼編寫這裏會用到 JDBC 數據庫鏈接因此提早寫一個 JDBC 鏈接數據庫的工具類：jsp

package com.xcl.Tools;

import java.sql.*;

public class JDBCTools {
    public static Connection getConnection(){
        Connection connection = null;
        try {
            //1.加載驅動
            Class.forName("com.mysql.cj.jdbc.Driver");
            //2.獲取鏈接
            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 層代碼的編寫仍是老樣子先寫一個接口接口裏面寫好須要實現的 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);
}

再寫一個實現類實現接口裏面定義的方法：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 {
    /**
     * 查詢
     *
     * @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;
    }

    /**
     *
     * 刪除
     *
     * @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);
        }
    }
}

接下來就是要編寫先後端交互的代碼也就是 controller 層的編寫

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;
        }

    }
}

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