This project contains test classes to get familiar with Spring Cloud Stream and Kafka Streams.
The source code and the configuration contains comments that shall help to understand pitfalls and what is needed for which behaviour.
The configuration use-native-encoding and use-native-decoding
in the application.yml controls two different sections.
For KStreams the part spring.cloud.stream.kafka.streams.bindings becomes
relevant. Because it needs the Serdes. The normal serializer/deserializer configurations at
spring.kafka.consumer/spring.kafka.producer was completely ignored.
On the other hand for normal Messages, the spring.kafka configuration is
used when use-native-encoding/use-native-decoding is enabled.
Please be careful, when not activating this flag with Spring messaging and CloudEvents.
The MessageConverter will unwrap the payload and create a Message<byte[]> which results
in exceptions.
The function definition is needed and but does not represent the order of the functions.
I copied the libraries I used from several examples. But have not checked at the beginning what they do. So I want to give some advises.
- spring-cloud-stream-test-binder: Is good to mock the bindings to kafka, if you don't want to start an actual kafka. If you want to combine KafkaListener in your tests and streams in your production code, don't activate this library.
- spring-kafka-test: I decided to use a Kafka testcontainer. If you prefer the embedded kafka (i.e. has much more convenience features) feel free to use this library, but don't forget to disable the testcontainer libraries.
- kafka-streams-test-utils: If you do not want to use KafkaListener or KafkaTemplate, use this library to create Streams with the TestTopologyDriver.
To let the application run locally, start a kafka via terminal command
docker-compose up -d
This also starts an akhq instance, available at http://localhost:7080 to view the messages and consumer groups.
Then start the application via run configuration.