使用jdbd和三层结构写一个学生管理系统

学生管理系统是一个比较典型的 CRUD 应用，使用 JDBC 和三层结构可以实现对学生信息的增、删、改、查等操作。

首先，我们需要在数据库中创建一个学生表，例如：

CREATE TABLE student (
  id INT PRIMARY KEY AUTO_INCREMENT,
  name VARCHAR(50) NOT NULL,
  gender VARCHAR(10) NOT NULL,
  age INT NOT NULL,
  department VARCHAR(50) NOT NULL
);

然后，我们可以定义一个 Student 类来表示学生信息，例如：

public class Student {
    private int id;
    private String name;
    private String gender;
    private int age;
    private String department;
 
    // 构造方法、getter 和 setter 略
}

接着，我们可以定义一个 DAO 层来操作数据库中的学生表，例如：

public class StudentDao {
    // 数据库连接参数
    private static final String URL = "jdbc:mysql://localhost:3306/test";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "123456";
 
    // 获取连接
    private Connection getConnection() throws SQLException {
        return DriverManager.getConnection(URL, USERNAME, PASSWORD);
    }
 
    // 添加学生
    public void addStudent(Student student) {
        try (Connection conn = getConnection();
             PreparedStatement stmt = conn.prepareStatement("INSERT INTO student (name, gender, age, department) VALUES (?, ?, ?, ?)")) {
            stmt.setString(1, student.getName());
            stmt.setString(2, student.getGender());
            stmt.setInt(3, student.getAge());
            stmt.setString(4, student.getDepartment());
            stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
 
    // 删除学生
    public void deleteStudent(int id) {
        try (Connection conn = getConnection();
             PreparedStatement stmt = conn.prepareStatement("DELETE FROM student WHERE id = ?")) {
            stmt.setInt(1, id);
            stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
 
    // 修改学生
    public void updateStudent(Student student) {
        try (Connection conn = getConnection();
             PreparedStatement stmt = conn.prepareStatement("UPDATE student SET name = ?, gender = ?, age = ?, department = ? WHERE id = ?")) {
            stmt.setString(1, student.getName());
            stmt.setString(2, student.getGender());
            stmt.setInt(3, student.getAge());
            stmt.setString(4, student.getDepartment());
            stmt.setInt(5, student.getId());
            stmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
 
    // 获取学生列表
    public List<Student> getStudentList() {
        List<Student> studentList = new ArrayList<>();
        try (Connection conn = getConnection();
             PreparedStatement stmt = conn.prepareStatement("SELECT * FROM student")) {
            ResultSet rs = stmt.executeQuery();
            while (rs.next()) {
                Student student = new Student();
                student.setId(rs.getInt("id"));
                student.setName(rs.getString("name"));
                student.setGender(rs.getString("gender"));
                student.setAge(rs.getInt("age"));
                student.setDepartment(rs.getString("department"));
                studentList.add(student);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return studentList;
    }
 
    // 根据 ID 获取学生
    public Student getStudentById(int id) {
        Student student = null;
        try (Connection conn = getConnection();
             PreparedStatement stmt = conn.prepareStatement("SELECT * FROM student WHERE id = ?")) {
            stmt.setInt(1, id);
            ResultSet rs = stmt.executeQuery();
            if (rs.next()) {
                student = new Student();
                student.setId(rs.getInt("id"));
                student.setName(rs.getString("name"));
                student.setGender(rs.getString("gender"));
                student.setAge(rs.getInt("age"));
                student.setDepartment(rs.getString("department"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return student;
    }
}

最后，我们可以定义一个 Service 层来调用 DAO 层的方法，例如：

public class StudentService {
    private StudentDao studentDao = new StudentDao();
 
    // 添加学生
    public void addStudent(Student student) {
        studentDao.addStudent(student);
    }
 
    // 删除学生
    public void deleteStudent(int id) {
        studentDao.deleteStudent(id);
    }
 
    // 修改学生
    public void updateStudent(Student student) {
        studentDao.updateStudent(student);
    }
 
    // 获取学生列表
    public List<Student> getStudentList() {
        return studentDao.getStudentList();
    }
 
    // 根据 ID 获取学生
    public Student getStudentById(int id) {
        return studentDao.getStudentById(id);
    }
}

这样，我们就实现了一个简单的学生管理系统，可以通过调用 Service 层的方法来对学生信息进行增、删、改、查等操作。