public static MqttSubscribeMessage subscribeMessage(List<MqttTopicSubscription> mqttTopicSubscriptions,
		int messageId) {
	MqttSubscribePayload mqttSubscribePayload = new MqttSubscribePayload(mqttTopicSubscriptions);
	MqttFixedHeader mqttFixedHeader = new MqttFixedHeader(MqttMessageType.SUBSCRIBE, false, MqttQoS.AT_LEAST_ONCE,
			false, 0);
	MqttMessageIdVariableHeader mqttMessageIdVariableHeader = MqttMessageIdVariableHeader.from(messageId);
	return new MqttSubscribeMessage(mqttFixedHeader, mqttMessageIdVariableHeader, mqttSubscribePayload);
}
 

public static MqttSubscribeMessage subscribe(int messageId, MqttTopicSubscription... topicSubscriptions) {
	int topicNameSize = 0;
	int topicCount = topicSubscriptions.length;

	for (MqttTopicSubscription item : topicSubscriptions) {
		topicNameSize += item.topicName().getBytes(CharsetUtil.UTF_8).length;
	}

	MqttFixedHeader fixedHeader = new MqttFixedHeader(MqttMessageType.SUBSCRIBE, false, MqttQoS.AT_LEAST_ONCE,
			false, 2 + topicNameSize + topicCount);
	MqttMessageIdVariableHeader variableHeader = MqttMessageIdVariableHeader.from(messageId);
	MqttSubscribePayload payload = new MqttSubscribePayload(Lists.newArrayList(topicSubscriptions));

	return new MqttSubscribeMessage(fixedHeader, variableHeader, payload);
}