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spring-cloud-stream/docs/modules/ROOT/pages/spring-cloud-stream.adoc
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[[spring-cloud-stream-reference]]
= Spring Cloud Stream Reference Documentation
:page-section-summary-toc: 1
:doctype: book
// ======================================================================================
[[preface]]
== Preface
This section goes into more detail about how you can work with Spring Cloud Stream.
It covers topics such as creating and running stream applications.
[[spring-cloud-stream-overview-introducing]]
== Introducing Spring Cloud Stream
Spring Cloud Stream is a framework for building message-driven microservice applications.
Spring Cloud Stream builds upon Spring Boot to create standalone, production-grade Spring applications and uses Spring Integration to provide connectivity to message brokers.
It provides opinionated configuration of middleware from several vendors, introducing the concepts of persistent publish-subscribe semantics, consumer groups, and partitions.
By adding `spring-cloud-stream` dependencies to the classpath of your application, you get immediate connectivity
to a message broker exposed by the provided `spring-cloud-stream` binder (more on that later), and you can implement your functional
requirement, which is run (based on the incoming message) by a `java.util.function.Function`.
The following listing shows a quick example:
[source,java]
----
@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();
}
}
----
The following listing shows the corresponding test:
[source,java]
----
@SpringBootTest(classes = SampleApplication.class)
@Import({TestChannelBinderConfiguration.class})
class BootTestStreamApplicationTests {
@Autowired
private InputDestination input;
@Autowired
private OutputDestination output;
@Test
void contextLoads() {
input.send(new GenericMessage<byte[]>("hello".getBytes()));
assertThat(output.receive().getPayload()).isEqualTo("HELLO".getBytes());
}
}
----
[[main-concepts]]
== Main Concepts
Spring Cloud Stream provides a number of abstractions and primitives that simplify the writing of message-driven microservice applications.
The rest of this reference manual provides additional details.