利用Java web学生增删改查的dao类

以下是一个示例的Java Web学生增删改查的DAO类：

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 sql = "INSERT INTO students (name, age, grade) VALUES (?, ?, ?)";
        PreparedStatement statement = connection.prepareStatement(sql);
        statement.setString(1, student.getName());
        statement.setInt(2, student.getAge());
        statement.setString(3, student.getGrade());
        statement.executeUpdate();
        statement.close();
    }

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

    public void updateStudent(Student student) throws SQLException {
        String sql = "UPDATE students SET name = ?, age = ?, grade = ? WHERE id = ?";
        PreparedStatement statement = connection.prepareStatement(sql);
        statement.setString(1, student.getName());
        statement.setInt(2, student.getAge());
        statement.setString(3, student.getGrade());
        statement.setInt(4, student.getId());
        statement.executeUpdate();
        statement.close();
    }

    public List<Student> getAllStudents() throws SQLException {
        List<Student> students = new ArrayList<>();
        String sql = "SELECT * FROM students";
        PreparedStatement statement = connection.prepareStatement(sql);
        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);
        }
        resultSet.close();
        statement.close();
        return students;
    }
}

这个示例中的DAO类包含了增加学生、删除学生、更新学生以及获取所有学生的方法。这些方法通过执行SQL语句与数据库进行交互来完成对学生信息的操作。其中，每个方法都接收一个Connection对象作为参数，这个Connection对象用于与数据库建立连接。可以根据具体的需求进行方法的调用和使用。