结合本学期所学知识，利用三层结构+JDBC开发一个简单的*****管理系统，题目可以是学生成绩管理系统、图书管理系统、企业员工管理系统等，

好的，我可以为您提供一个简单的学生成绩管理系统的示例。

首先，我们需要设计数据库表和字段。

我们可以创建一个名为“student”的表，其中包含以下字段：

- id：学生ID，主键，自增长
- name：学生姓名，字符串类型
- gender：学生性别，字符串类型
- age：学生年龄，整数类型
- grade：学生年级，字符串类型
- score：学生成绩，浮点数类型

接下来，我们可以创建一个Java项目，并使用JDBC连接到MySQL数据库。

在项目中，我们可以创建三个Java类：

- Student类：用于表示学生对象
- StudentDAO类：用于与数据库进行交互，包括添加、删除、更新和查询学生信息等操作
- Main类：用于测试StudentDAO类中的方法

下面是Student类的代码：

public class Student {
    private int id;
    private String name;
    private String gender;
    private int age;
    private String grade;
    private float score;
    
    public Student(int id, String name, String gender, int age, String grade, float score) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.age = age;
        this.grade = grade;
        this.score = score;
    }
    
    public int getId() {
        return id;
    }
    
    public String getName() {
        return name;
    }
    
    public String getGender() {
        return gender;
    }
    
    public int getAge() {
        return age;
    }
    
    public String getGrade() {
        return grade;
    }
    
    public float getScore() {
        return score;
    }
}

下面是StudentDAO类的代码：

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class StudentDAO {
    private Connection conn;
    
    public StudentDAO() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "123456");
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }
    }
    
    public void addStudent(Student student) {
        String sql = "INSERT INTO student(name, gender, age, grade, score) VALUES (?, ?, ?, ?, ?)";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1, student.getName());
            ps.setString(2, student.getGender());
            ps.setInt(3, student.getAge());
            ps.setString(4, student.getGrade());
            ps.setFloat(5, student.getScore());
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    public void updateStudent(Student student) {
        String sql = "UPDATE student SET name=?, gender=?, age=?, grade=?, score=? WHERE id=?";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1, student.getName());
            ps.setString(2, student.getGender());
            ps.setInt(3, student.getAge());
            ps.setString(4, student.getGrade());
            ps.setFloat(5, student.getScore());
            ps.setInt(6, student.getId());
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    public void deleteStudent(int id) {
        String sql = "DELETE FROM student WHERE id=?";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, id);
            ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    public Student getStudentById(int id) {
        String sql = "SELECT * FROM student WHERE id=?";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, id);
            ResultSet rs = ps.executeQuery();
            if (rs.next()) {
                String name = rs.getString("name");
                String gender = rs.getString("gender");
                int age = rs.getInt("age");
                String grade = rs.getString("grade");
                float score = rs.getFloat("score");
                return new Student(id, name, gender, age, grade, score);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
    
    public List<Student> getAllStudents() {
        String sql = "SELECT * FROM student";
        List<Student> students = new ArrayList<>();
        try {
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery(sql);
            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                String gender = rs.getString("gender");
                int age = rs.getInt("age");
                String grade = rs.getString("grade");
                float score = rs.getFloat("score");
                students.add(new Student(id, name, gender, age, grade, score));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return students;
    }
    
    public void closeConnection() {
        try {
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

最后是Main类的代码，用于测试StudentDAO类中的方法：

import java.util.List;

public class Main {
    public static void main(String[] args) {
        StudentDAO dao = new StudentDAO();
        
        // 添加学生
        Student student1 = new Student(0, "张三", "男", 20, "大一", 85.0f);
        dao.addStudent(student1);
        Student student2 = new Student(0, "李四", "女", 19, "大一", 90.0f);
        dao.addStudent(student2);
        
        // 获取所有学生信息
        List<Student> students = dao.getAllStudents();
        for (Student student : students) {
            System.out.println(student.getId() + " " + student.getName() + " " + student.getGender() + " " + student.getAge() + " " + student.getGrade() + " " + student.getScore());
        }
        
        // 修改学生信息
        Student student3 = new Student(1, "王五", "男", 21, "大二", 95.0f);
        dao.updateStudent(student3);
        
        // 获取指定学生信息
        Student student4 = dao.getStudentById(2);
        System.out.println(student4.getId() + " " + student4.getName() + " " + student4.getGender() + " " + student4.getAge() + " " + student4.getGrade() + " " + student4.getScore());
        
        // 删除学生信息
        dao.deleteStudent(2);
        
        // 关闭数据库连接
        dao.closeConnection();
    }
}

这个简单的学生成绩管理系统就完成了，您可以根据需要进行修改和扩展。