用javaweb写一下学生信息管理系统增删改查dao类代码

以下是一个简单的学生信息管理系统的增删改查的DAO类代码示例：

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();
        statement.close();
    }

    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();
        statement.close();
    }

    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();
        statement.close();
    }

    public Student getStudent(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);
        }

        resultSet.close();
        statement.close();
        return null;
    }

    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");
            students.add(new Student(id, name, age));
        }

        resultSet.close();
        statement.close();
        return students;
    }
}

这是一个简单的DAO类，用于对学生信息进行增删改查操作。其中，使用了PreparedStatement来执行SQL语句，并通过Connection对象来获取数据库连接。在增加、删除、更新和查询学生信息时，都使用了相应的SQL语句，并将参数设置到PreparedStatement对象中。在查询学生信息时，使用ResultSet对象获取查询结果，并将结果封装成Student对象。在获取所有学生信息时，使用List集合存储多个Student对象，并将其返回。