Kafka Camunda Example

A sample Camunda process that interacts with Kafka.

Show me the important parts!

How does it work?

The application has a Rest API Controller that post messages in two topics: start-process-message-topic and intermediate-message-topic. The request body of the api uses the POJO CamundaMessageDto.

Those two topics are also listened by two methods in a Consumer Class. One method can trigger a message start and another a message intermediate event.

The functionality to correlate a Camunda message is available in the Message Service Class.

Last but not least, the service task after the intermediate message posts a message back into Kafka in the topic service-task-message-topic.

This project was heavily based in the following tutorial: https://www.baeldung.com/spring-kafka

For more information on Camunda message correlation, please check: https://docs.camunda.org/manual/7.12/reference/bpmn20/events/message-events/

How to use it?

Start Apache Kafka in the default manner. Please check it here: https://kafka.apache.org/quickstart

The topics configuration is done automatically by the class KafkaTopicConfig.

You can start by running a POST against the endpoint http://localhost:8080/message-process/start:

{
	"correlationId":"12345",
	"dto":{
		"requester":"someone asked for it...",
		"amount":1000,
		"preApproved":true
	}
}

This will create an instance of the process showed above by posting a message to a topic "start-process-message-topic". This message is picked up by the listener in the class StartMessageProcessConsumer and will correlate the start event message event.

You can finish the intermediate message by running a POST against the endpoint http://localhost:8080/message-process/intermediate

You should use the same correlation id as before, so you can consume the message of the process that was created.

At the end of the process, you should see a JSON posted in the topic service-task-message-topic.

Environment Restrictions

This project uses Camunda 7.12.5-ee with Spring Boot.

Known Limitations

Event subprocess can be implemented by listening a message.