https://knallisworld.de/blog/2016/03/26/expose-a-java-method-with-amqp-and-spring-reloaded-with-java-dsl/

ApiGateway1.java

@MessagingGateway
public interface ApiGateway {
	@Gateway(requestChannel = "requestChannel", replyChannel = "resultChannel")
	Response handle(Request request);
}

ApiGateway2.java

@MessagingGateway
public interface ApiGateway {
	@Gateway(requestChannel = "requestChannel", replyChannel = "resultChannel")
	CompletableFuture<Response> handle(Request request);
}

ConfigClient.java

@Configuration
public class ConfigClient {
  @Bean public IntegrationFlow flow() {
		return IntegrationFlows.from(MessageChannels.publishSubscribe("requestChannel"))
				.transform(Transformers.toJson(mapper()))
				.handle(Amqp.outboundGateway(amqpTemplate).routingKey("queue"))
				.transform(Transformers.fromJson(Response.class, mapper()))
				.channel(MessageChannels.direct("responseChannel"))
				.get();
	}
}

ConfigServer.java

@Configuration
public class ConfigServer {
  @Autowired ConnectionFactory connectionFactory;
	@Autowired ApiImpl api;

	@Bean public JsonObjectMapper<?, ?> mapper() {
		return new Jackson2JsonObjectMapper();
	}

	@Bean public IntegrationFlow flow() {
		return IntegrationFlows.from(
				Amqp.inboundGateway(connectionFactory, "queue")
						.errorChannel("errorChannel"))
				.transform(Transformers.fromJson(Request.class, mapper()))
				.handle(Request.class, (request, headers) -> api.handle(request))
				.transform(Transformers.toJson(mapper()))
				.get();
	}
}