Confusing why append '/' to the end of topic name?

[ferrirW]

Have not find related explain, please give some description.

rocketmq-mqtt/mqtt-common/src/main/java/org/apache/rocketmq/mqtt/common/util/TopicUtils.java

Lines 27 to 44 in 9939eab

	/**
	* t1/t2/t3/
	*
	* @param topic
	* @return
	*/
	public static String normalizeTopic(String topic) {
	if (topic == null) {
	return null;
	}
	if (!topic.contains(Constants.MQTT_TOPIC_DELIMITER)) {
	return topic;
	}
	if (!topic.endsWith(Constants.MQTT_TOPIC_DELIMITER)) {
	return topic + Constants.MQTT_TOPIC_DELIMITER;
	}
	return topic;
	}

[tianliuliu]

ping @pingww

[pingww]

The main reason is to format it into a fixed format. As for the addition of a /, the reason is that there is a matching path in the trie, which can indeed be optimized.

[ferrirW]

ok, thanks for answering.

And found some code can be optimized:

1. ADDFLAG & JINFLAG should be replaced with PLUS_SIGN & NUMBER_SIGN refer to unicode

2. Some redundant containsKey before putIfAbsent()

3. buildIntanceName -> buildInstanceName

4. TopicUtils.isMatch("t/t1/t2/", "t/#/t2/") should be false but return true now.(I know some client will do this check like poho, however, it is better for the server to do a validation as well)

[pingww]

"t/#/t2/" is not valid according to the mqtt protocol

[ferrirW]

"t/#/t2/" is not valid according to the mqtt protocol

yes, I just want to suggest server should do this check anyway, like: #25 (comment)