Spring Cloud Stream – Composed Functions or EIP

Spring Cloud Stream is a framework for creating highly scalable event-driven microservices that communicate over common messaging systems. The framework provides a versatile programming architecture based on well-known Spring idioms and best practices, such as support for persistent pub/sub semantics, consumer groups, and stateful partitioning.

Java

@SpringBootApplication
public class Application {
  public static void main(String[] args) {
    SpringApplication.run(Application.class, args);
  }

  @Bean
  public Function<String, String> uppercase() {
    return value -> value.toUpperCase();
  }
}

Spring Cloud Stream Core Building Blocks

• Message: The standard data format that producers and consumers use to exchange information with Destination Binders.
• Destination Binders: Parts in charge of offering integration with outside message platforms.
• Destination Bindings: A link between the application code that the end user provides and the external messaging services.

Composed Functions or EIP

Function Composition

A declarative method of composing many functions together is possible using SCF’s function composition feature. This is demonstrated by the example as below:

--spring.cloud.function.definition=uppercase|reverse

Enterprise Integration Patterns (EIP)

A collection of precisely defined and comprehended patterns, known as enterprise integration, patterns, enables you to characterize a business case. Filter, transformer, router, and so forth are a few examples. Click this link to learn more about EIP. Spring provides a reference implementation of EIP using the Spring Integration framework.

IntegrationFlow.fromChannel(inputChannel)
        .transform(uppercase)
        .transform(reverse);

Using Two Applications Spring Cloud Stream – Composed Functions

The functionality of the two apps in the Stream (http | transformer) is combined into a single application, which we construct and register. The new stream is then put into use, and we confirm that the output matches that of the prior example.

Java

@SpringBootApplication
@Import(org.springframework.cloud.stream.app.http.source.HttpSourceConfiguration.class)
public class HttpSourceRabbitApplication {

    @Bean
    public Function<String, String> upper() {
        return value -> value.toUpperCase();
    }

    @Bean
    public Function<String, String> concat() {
        return value -> "Hello "+ value;
    }


    public static void main(String[] args) {
        SpringApplication.run(HttpSourceRabbitApplication.class, args);
    }
}

Conclusion

So, this is Spring Cloud Stream – Composed Functions or EIP. For orchestrating capabilities that are aligned in sequence, SCF Composition is a better fit, whereas SI is a better option for anything else that falls within the EIP category.