写一下学生信息管理系统DAO类

学生信息管理系统DAO类是用于访问数据库的类，它负责与数据库的交互，包括增删改查等操作。下面是一个示例的学生信息管理系统DAO类的代码：

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 StudentDAO {
    private Connection connection;

    public StudentDAO(Connection connection) {
        this.connection = connection;
    }

    public void addStudent(Student student) throws SQLException {
        String query = "INSERT INTO students (id, name, age) VALUES (?, ?, ?)";
        PreparedStatement statement = connection.prepareStatement(query);
        statement.setInt(1, student.getId());
        statement.setString(2, student.getName());
        statement.setInt(3, student.getAge());
        statement.executeUpdate();
    }

    public void updateStudent(Student student) throws SQLException {
        String query = "UPDATE students SET name = ?, age = ? WHERE id = ?";
        PreparedStatement statement = connection.prepareStatement(query);
        statement.setString(1, student.getName());
        statement.setInt(2, student.getAge());
        statement.setInt(3, student.getId());
        statement.executeUpdate();
    }

    public void deleteStudent(int id) throws SQLException {
        String query = "DELETE FROM students WHERE id = ?";
        PreparedStatement statement = connection.prepareStatement(query);
        statement.setInt(1, id);
        statement.executeUpdate();
    }

    public List<Student> getAllStudents() throws SQLException {
        List<Student> students = new ArrayList<>();
        String query = "SELECT * FROM students";
        PreparedStatement statement = connection.prepareStatement(query);
        ResultSet resultSet = statement.executeQuery();
        while (resultSet.next()) {
            int id = resultSet.getInt("id");
            String name = resultSet.getString("name");
            int age = resultSet.getInt("age");
            Student student = new Student(id, name, age);
            students.add(student);
        }
        return students;
    }

    public Student getStudentById(int id) throws SQLException {
        String query = "SELECT * FROM students WHERE id = ?";
        PreparedStatement statement = connection.prepareStatement(query);
        statement.setInt(1, id);
        ResultSet resultSet = statement.executeQuery();
        if (resultSet.next()) {
            String name = resultSet.getString("name");
            int age = resultSet.getInt("age");
            return new Student(id, name, age);
        } else {
            return null;
        }
    }
}

上述代码中，StudentDAO类包含了一些常用的数据库操作方法，如添加学生、更新学生、删除学生、获取所有学生和根据ID获取学生信息。这些方法通过预编译的SQL语句与数据库进行交互，并将结果封装成相应的对象返回。