Build Reactive RSocket Services with Spring Retrosocket: A Step‑by‑Step Guide

Background

Recently the hottest topic in the Chinese tech community is the release of Apache Dubbo 3.0. The most important feature of Dubbo 3 is the adoption of HTTP/2 as the underlying transport protocol and protobuf as the serialization protocol, a combination also used by gRPC. RSocket was not chosen as a complementary solution for reactive programming.

RSocket is a new, language‑agnostic, seventh‑layer application network protocol. It is a bidirectional, multiplexed, message‑based binary protocol with reactive‑stream back‑pressure. Besides the traditional Request/Response model of HTTP, RSocket also supports Fire‑And‑Forget (no response), Stream (one‑way stream), and Channel (bidirectional stream).

The fundamentals of RSocket can be studied in the article "RSocket | The Perfect Alternative to REST".

This article focuses on using the newly incubated Spring project spring‑retrosocket .

spring‑retrosocket provides an annotation‑driven RSocket client, shielding developers from the complexity of the rsocket‑java SDK.

Create RSocket Server

Create a Spring Boot project and add the required dependency.

<code>&lt;dependency&gt;
  &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
  &lt;artifactId&gt;spring-boot-starter-rsocket&lt;/artifactId&gt;
&lt;/dependency&gt;</code>

Specify the RSocket server port.

<code>spring.rsocket.server.port=8848</code>

Define the request‑response handling channel using

@MessageMapping

to set the route.

<code>@Controller
public class GreetingsController {
  @MessageMapping("request-response")
  Mono&lt;String&gt; reqResponse(@Payload String payload) {
    log.info("Received RR request: {}", payload);
    return Mono.just("Hello, " + payload);
  }
}
</code>

2. Create Client with spring‑retrosocket

Generate a new project with Spring Initializr.

Dependency

Version

spring‑retrosocket

0.0.1‑SNAPSHOT

Spring Boot

2.5.2

<code>&lt;dependency&gt;
  &lt;groupId&gt;org.springframework.retrosocket&lt;/groupId&gt;
  &lt;artifactId&gt;spring-retrosocket&lt;/artifactId&gt;
  &lt;version&gt;0.0.1-SNAPSHOT&lt;/version&gt;
&lt;/dependency&gt;</code>

Add the Spring Maven repositories.

<code>&lt;repositories&gt;
  &lt;repository&gt;
    &lt;id&gt;spring-milestones&lt;/id&gt;
    &lt;name&gt;Spring Milestones&lt;/name&gt;
    &lt;url&gt;https://repo.spring.io/milestone&lt;/url&gt;
  &lt;/repository&gt;
  &lt;repository&gt;
    &lt;id&gt;spring-snapshots&lt;/id&gt;
    &lt;name&gt;Spring Snapshots&lt;/name&gt;
    &lt;url&gt;https://repo.spring.io/snapshot&lt;/url&gt;
    &lt;snapshots&gt;
      &lt;enabled&gt;true&lt;/enabled&gt;
    &lt;/snapshots&gt;
  &lt;/repository&gt;
&lt;/repositories&gt;</code>

3. Basic Usage

Enable RSocket client support in your Java code with

@EnableRSocketClient

and define an

RSocketRequester

bean.

<code>@SpringBootApplication
@EnableRSocketClients
class RSocketClientApplication {
  @Bean
  RSocketRequester requester(RSocketRequester.Builder builder) {
    return builder.connectTcp("localhost", 8888).block();
  }
}
</code>

Define an RSocket client interface similar to FeignClient .

<code>@RSocketClient
interface GreetingClient {
  @MessageMapping("request-response")
  Mono&lt;GreetingResponse&gt; requestResponse(Mono&lt;String&gt; name);
}
</code>

Test the client.

<code>@SpringBootTest
class DemoApplicationTests {
  @Autowired
  private GreetingClient greetingClient;

  @Test
  void testGreetingClient() {
    Mono&lt;String&gt; stringMono = greetingClient.requestResponse(Mono.just("lengleng"));
    System.out.println(stringMono.block());
  }
}
</code>

spring‑retrosocket source code is available at https://github.com/spring-projects-experimental/spring-retrosocket .