Sending and receiving messages with Spring Cloud Stream code example

Spring Cloud Stream provides a streaming abstraction over messaging, based on the publish and subscribe integration pattern. Spring Cloud Stream comes with out of the box support for Apache Kafka and RabbitMQ but can be extended to support other messaging brokers using custom binders.

The Message class

public class MyMessage {
    private String attributeFirst = null;
    private String attributeSecond = null;
    ...

Spring Cloud Stream comes with default input and output channels, Sink and Source.

To publish a message

import org.springframework.cloud.stream.messaging.Source;

@EnableBinding(Source.class)
public class MyPublisher {

@Autowired private Source source;

public String processMessage(MyMessage message) {
    source.output().send(MessageBuilder.withPayload(message).build());
    ...

To receive messages

import org.springframework.cloud.stream.messaging.Sink;

@EnableBinding(Sink.class)
public class MySubscriber {

@StreamListener(target = Sink.INPUT)
public void receive(MyMessage message) {
    LOG.info("Received: {}",message);
    ...

To bind to RabbitMQ, include in build.gradle

    implementation('org.springframework.cloud:spring-cloud-starter-streamrabbit')

The configuration for the publisher

spring.cloud.stream:
    default.contentType: application/json
    bindings.output.destination: mydestination

The configuration for the subscriber

spring.cloud.stream:
    default.contentType: application/json
    bindings.input.destination: mydestination

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