public static boolean isValid(final String userName, final byte[] passwordInBytes) {
        String password = new String(passwordInBytes);

        if (StringUtils.isEmpty(password) || StringUtils.isEmpty(userName)) {
            return false;
        }

        return MqttContext.userName.equals(userName) && MqttContext.password.equals(password);
    }
Whether userName and password are correct.
@param userName userName
@param passwordInBytes passwordInBytes
@return true is correct, false unavailable.
shenyu-protocol/shenyu-protocol-mqtt/src/main/java/org/apache/shenyu/protocol/mqtt/MqttContext.java