Mqttv5PahoMessageDrivenChannelAdapter.addTopic(topic, qos) throws NPE

[mrpiggi]

In what version(s) of Spring Integration are you seeing this issue?

5.5.9 and prior (5.5.5)

Describe the bug

Creating a new Mqttv5PahoMessageDrivenChannelAdapter and using addTopic(topic, qos) before onInit() was called throws a NPE as this.mqttClient.subscribe(topic, qos) is invoked. Same with Mqttv5PahoMessageDrivenChannelAdapter.removeTopic(String...) and this.mqttClient.unsubscribe(topic).

To Reproduce

final Mqttv5PahoMessageDrivenChannelAdapter adapter = new Mqttv5PahoMessageDrivenChannelAdapter(options, id);
adapter.addTopic(topic, 1);

Workaround

final Mqttv5PahoMessageDrivenChannelAdapter adapter = new Mqttv5PahoMessageDrivenChannelAdapter(options, id, topic);
adapter.setQos(1);

Expected behavior

Topic registration or removal without calling IMqttAsyncClient.subscribe(topic, qos) or IMqttAsyncClient.unsubscribe(String...) when not initialized yet.

The comparison between Mqttv5PahoMessageDrivenChannelAdapter and MqttPahoMessageDrivenChannelAdapter is quite obvious.

spring-integration/spring-integration-mqtt/src/main/java/org/springframework/integration/mqtt/inbound/Mqttv5PahoMessageDrivenChannelAdapter.java

Lines 214 to 242 in 8c57cb7

	@Override
	public void addTopic(String topic, int qos) {
	this.topicLock.lock();
	try {
	this.mqttClient.subscribe(topic, qos).waitForCompletion(getCompletionTimeout());
	super.addTopic(topic, qos);
	}
	catch (MqttException ex) {
	throw new MessagingException("Failed to subscribe to topic " + topic, ex);
	}
	finally {
	this.topicLock.unlock();
	}
	}
	@Override
	public void removeTopic(String... topic) {
	this.topicLock.lock();
	try {
	this.mqttClient.unsubscribe(topic).waitForCompletion(getCompletionTimeout());
	super.removeTopic(topic);
	}
	catch (MqttException ex) {
	throw new MessagingException("Failed to unsubscribe from topic(s) " + Arrays.toString(topic), ex);
	}
	finally {
	this.topicLock.unlock();
	}
	}

spring-integration/spring-integration-mqtt/src/main/java/org/springframework/integration/mqtt/inbound/MqttPahoMessageDrivenChannelAdapter.java

Lines 222 to 255 in 8c57cb7

	@Override
	public void addTopic(String topic, int qos) {
	this.topicLock.lock();
	try {
	super.addTopic(topic, qos);
	if (this.client != null && this.client.isConnected()) {
	this.client.subscribe(topic, qos);
	}
	}
	catch (MqttException e) {
	super.removeTopic(topic);
	throw new MessagingException("Failed to subscribe to topic " + topic, e);
	}
	finally {
	this.topicLock.unlock();
	}
	}
	@Override
	public void removeTopic(String... topic) {
	this.topicLock.lock();
	try {
	if (this.client != null && this.client.isConnected()) {
	this.client.unsubscribe(topic);
	}
	super.removeTopic(topic);
	}
	catch (MqttException e) {
	throw new MessagingException("Failed to unsubscribe from topic(s) " + Arrays.toString(topic), e);
	}
	finally {
	this.topicLock.unlock();
	}
	}

[artembilan]

Confirmed.

Feel free to contribute the fix: https://github.com/spring-projects/spring-integration/blob/main/CONTRIBUTING.adoc

Thank you!