java 保存中文mysql乱码

CREATE DATABASE mydb CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
USE mydb;
CREATE TABLE mytable (
    id INT PRIMARY KEY,
    name VARCHAR(255)
) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

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

public class MySQLConnection {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/mydb?useUnicode=yes&characterEncoding=UTF-8";
        String user = "username";
        String password = "password";

        try (Connection conn = DriverManager.getConnection(url, user, password)) {
            System.out.println("Connected to the database!");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

-Dfile.encoding=UTF-8

export LANG=en_US.UTF-8
export LANGUAGE=en_US:en
export LC_ALL=en_US.UTF-8