Update:

• Here is the Spring Cloud Stream Kafka producer tutorial.
• Here is how to connect Spring Cloud Stream Kafka to Azure Event Hub.

Spring Cloud Stream is a very complex topic and a remarkable piece of technology. It builds on other intricate Spring technologies like Spring Integration and Spring Cloud Function, and when you add Apache Kafka to the mix, you have a steep learning curve on your hands.

There is a lot of documentation to read and comprehend, and I do not think it helps that your first interaction with the technology is by showing off. Here is the sample in the “Introducing Spring Cloud Stream” section.

@SpringBootApplication
public class SampleApplication {
    public static void main(String[] args) {
        SpringApplication.run(SampleApplication.class, args);
    }
    @Bean
    public Function<String, String> uppercase() {
        return value -> value.toUpperCase();
    }
}

That supposedly is a fully functioning application. The uppercase() method consumes and produces simultaneously, essentially turning it into a way software can pleasure itself. To understand this example, you must know about all the Spring Boot auto-configuration magic happening in the background. Otherwise, it is an opaque magical, and indecipherable showpiece.

This post will show a practical example of a simple consumer application receiving messages from a Kafka cluster. This was my use case, and while the documentation contains a ton of helpful information, it only succeeded in confusing me at first, coming to the technology with fresh eyes. As a result, it took me a long time to put together all the pieces before I understood what was going on.