国际验证码短信
全球验证短信，稳定送达

import org.apache.commons.lang3.StringUtils;
import org.springframework.util.DigestUtils;
import java.util.TreeMap;
import java.util.Map;

public class InternationalSms {
    public static void main(String[] args) {
        String account = "IM6742671";
        String password = "4Z7bMS1eLI6895";
        String nonce = String.valueOf(System.currentTimeMillis());
        String mobile = "8618916198813";
        String msg = "【253云通讯】您的验证码是：1234";
        String url = "https://intapi.tig253.com/send/sms";

        // 排序参数
        TreeMap<String, String> paramMap = new TreeMap<>();
        paramMap.put("nonce", nonce);
        paramMap.put("account", account);
        paramMap.put("mobile", mobile);
        paramMap.put("msg", msg);

        // 加签
        StringBuilder sb = new StringBuilder();
        for (Map.Entry<String, String> entry : paramMap.entrySet()) {
            if (StringUtils.isNotBlank(entry.getValue())) {
                sb.append(entry.getKey()).append(entry.getValue());
            }
        }
        String sign = DigestUtils.md5DigestAsHex((sb + password).getBytes()).toLowerCase();

        // 发送（用 OkHttp / HttpClient 均可）
        // 此处省略发送，逻辑同你的demo
    }
}