用javaweb写一下学生信息管理系统DAO类

学生信息管理系统DAO类的代码如下所示：

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) {
        String query = "INSERT INTO students (id, name, age, grade) VALUES (?, ?, ?, ?)";
        try (PreparedStatement statement = connection.prepareStatement(query)) {
            statement.setInt(1, student.getId());
            statement.setString(2, student.getName());
            statement.setInt(3, student.getAge());
            statement.setString(4, student.getGrade());
            statement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    public void updateStudent(Student student) {
        String query = "UPDATE students SET name = ?, age = ?, grade = ? WHERE id = ?";
        try (PreparedStatement statement = connection.prepareStatement(query)) {
            statement.setString(1, student.getName());
            statement.setInt(2, student.getAge());
            statement.setString(3, student.getGrade());
            statement.setInt(4, student.getId());
            statement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    public void deleteStudent(int id) {
        String query = "DELETE FROM students WHERE id = ?";
        try (PreparedStatement statement = connection.prepareStatement(query)) {
            statement.setInt(1, id);
            statement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    
    public List<Student> getAllStudents() {
        List<Student> students = new ArrayList<>();
        String query = "SELECT * FROM students";
        try (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");
                String grade = resultSet.getString("grade");
                Student student = new Student(id, name, age, grade);
                students.add(student);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return students;
    }
    
    public Student getStudentById(int id) {
        Student student = null;
        String query = "SELECT * FROM students WHERE id = ?";
        try (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");
                String grade = resultSet.getString("grade");
                student = new Student(id, name, age, grade);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return student;
    }
}

以上代码实现了学生信息管理系统的DAO类，包含了添加、更新、删除、获取所有学生和根据ID获取学生等功能。请注意，此代码仅为示例，实际应用中可能需要根据具体需求进行修改和完善。