import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.net.URLEncoder;
import java.util.Base64;
        Long timestamp = System.currentTimeMillis();
        String secret = globalVarOf$dingtalkBotSecret;

        String stringToSign = timestamp + "\n" + secret;
        Mac mac = Mac.getInstance("HmacSHA256");
        mac.init(new SecretKeySpec(secret.getBytes("UTF-8"), "HmacSHA256"));
        byte[] signData = mac.doFinal(stringToSign.getBytes("UTF-8"));
        String sign = URLEncoder.encode(Base64.getEncoder().encodeToString(signData), "UTF-8");
        return "timestamp="+timestamp+"&sign="+sign;