java如何访问mysql数据库文件

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JDBCTest {
    public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            // 注册JDBC驱动
            Class.forName("com.mysql.cj.jdbc.Driver");

            // 打开连接
            System.out.println("连接数据库...");
            String url = "jdbc:mysql://localhost:3306/mydatabase";
            String user = "username";
            String password = "password";
            conn = DriverManager.getConnection(url, user, password);

            // 执行查询
            System.out.println("实例化Statement对象...");
            stmt = conn.createStatement();
            String sql;
            sql = "SELECT id, name, age FROM employees";
            ResultSet rs = stmt.executeQuery(sql);

            // 展开结果集数据库
            while (rs.next()) {
                // 通过列名获取
                int id = rs.getInt("id");
                String name = rs.getString("name");
                int age = rs.getInt("age");

                // 输出结果
                System.out.println("ID: " + id + ", 姓名: " + name + ", 年龄: " + age);
            }
            // 完成后关闭
            rs.close();
            stmt.close();
            conn.close();
        } catch (SQLException se) {
            // 处理JDBC错误
            se.printStackTrace();
        } catch (Exception e) {
            // 处理Class.forName错误
            e.printStackTrace();
        } finally {
            // 关闭资源
            try {
                if (stmt != null) stmt.close();
            } catch (SQLException se2) {
            } // 什么都不做
            try {
                if (conn != null) conn.close();
            } catch (SQLException se) {
                se.printStackTrace();
            }
        }
        System.out.println("Goodbye!");
    }
}