如何从jdbc模板查询中提取hashmap对象

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;

public class JdbcTemplateExample {
    public static void main(String[] args) {
        // 建立数据库连接
        Connection connection = null;
        try {
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydatabase", "username", "password");
            
            // 执行查询操作
            String sql = "SELECT * FROM mytable";
            PreparedStatement statement = connection.prepareStatement(sql);
            ResultSet resultSet = statement.executeQuery();
            
            // 提取查询结果
            Map<String, Object> resultMap = new HashMap<>();
            ResultSetMetaData metaData = resultSet.getMetaData();
            int columnCount = metaData.getColumnCount();
            
            while (resultSet.next()) {
                for (int i = 1; i <= columnCount; i++) {
                    String columnName = metaData.getColumnName(i);
                    Object columnValue = resultSet.getObject(i);
                    resultMap.put(columnName, columnValue);
                }
            }
            
            // 输出提取的HashMap对象
            System.out.println(resultMap);
            
            // 关闭连接
            resultSet.close();
            statement.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}