Bean injection for spring integration message handler - spring

Question

I am fairly new to spring and spring integration. What I'm trying to do: publish mqtt messages using spring integration.
Here is the code:
#Configuration
#IntegrationComponentScan
#Service
public class MQTTPublishAdapter {
private MqttConfiguration mqttConfiguration;
public MQTTPublishAdapter(MqttConfiguration mqttConfiguration) {
this.mqttConfiguration = mqttConfiguration;
}
#Bean
public MessageChannel mqttOutboundChannel() {
return new PublishSubscribeChannel();
}
#Bean
public MqttPahoClientFactory mqttClientFactory() {
DefaultMqttPahoClientFactory factory = new
DefaultMqttPahoClientFactory();
//... set factory details
return factory;
}
#Bean
#ServiceActivator(inputChannel = "mqttOutboundChannel")
public MQTTCustomMessageHandler mqttOutbound() {
String clientId = UUID.randomUUID().toString();
MQTTCustomMessageHandler messageHandler =
new MQTTCustomMessageHandler(clientId, mqttClientFactory());
//...set messagehandler details
return messageHandler;
}
//I extend this only because the publish method is protected and I want to
send messages to different topics
public class MQTTCustomMessageHandler extends MqttPahoMessageHandler {
//default constructors
public void sendMessage(String topic, String message){
MqttMessage mqttMessage = new MqttMessage();
mqttMessage.setPayload(message.getBytes());
try {
super.publish(topic, mqttMessage, null);
} catch (Exception e) {
log.error("Failure to publish message on topic " + topic,
e.getMessage());
}
}
}
This is the clase where I am trying to inject the Handler
#Service
public class MQTTMessagePublisher {
private MQTTCustomMessageHandler mqttCustomMessageHandler;
public MQTTMessagePublisher(#Lazy MQTTCustomMessageHandler
mqttCustomMessageHandler) {
this.mqttCustomMessageHandler = mqttCustomMessageHandler;
}
public void publishMessage(String topic, String message) {
mqttCustomMessageHandler.sendMessage(topic, message);
}
}
So my question is about how should I inject the bean I am trying to use because if I remove the #Lazy annotation it says that "Requested bean is currently in creation: Is there an unresolvable circular reference?". I do not have any circular dependencies as in the bean I only set some strings, so I'm guessing that I don't really understand how this should work.
Very sorry about the formating, it's one of my first questions around here.
Edit:
If I remove
#ServiceActivator(inputChannel = "mqttOutboundChannel")
and add
messageHandler.setChannelResolver((name) -> mqttOutboundChannel());
it works. I'm still unclear why the code crashes.

Answer 1

You show a lot of custom code, but not all of them.
It's really hard to answer to questions where it is only a custom code. Would be great to share as much info as possible. For example an external project on GitHub to let us to play and reproduce would be fully helpful and would save some time.
Nevertheless, I wonder what is your MQTTCustomMessageHandler. However I guess it is not a MessageHandler implementation. From here the #ServiceActivator annotation is not going to work properly since it is applied really for the mqttOutbound(), not whatever you expect. Or you need to move this annotation to your sendMessage() method in the MQTTCustomMessageHandler or have it as a MessageHandler.
On the other hand it is not clear why do you need that #ServiceActivator annotation at all since you call that method manually from the MQTTMessagePublisher.
Also it is not clear why you have so much custom code when Framework provides for your out-of-the-box channel adapter implementations.
Too many questions to your code, than possible answer...
See more info in the reference manual:
https://docs.spring.io/spring-integration/docs/current/reference/html/#annotations
https://docs.spring.io/spring-integration/docs/current/reference/html/#mqtt