Source Code: https://github.com/joexu01/rsocket-demo
0. 四种通信模式
让我们来简单复习一下 RSocket 的四种通信模式：
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即发即忘 - FireAndForget：立即发送一个请求，无需为这个请求发送响应报文。适用于监控埋点，日志上报等，这种场景下无需回执，丢失几个请求无伤大雅
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请求响应 - RequestResponse：请求方发送一条请求消息，响应方收到请求后并返回一条响应消息。传统的HTTP是典型的Request-Response
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流式响应 - RequestStream：请求方发送一个请求报文，响应方发回N个响应报文。传统的MQ是典型的RequestStream
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双向通道 - Channel：创建一个通道上下文，双方可以互相发送消息。IM是个典型的RequestChannel通讯场景
1. 客户端生成和解析路由信息
*本篇文章的客户端示例文件在 rsocket-client-raw/src/main/java/org/example/FourCommunicationScheme.java
我们使用 decodeRoute 和 encodeRoute 函数来解码和编码路由信息。
static String decodeRoute(ByteBuf metadata) { final RoutingMetadata routingMetadata = new RoutingMetadata(metadata); return routingMetadata.iterator().next(); } static ByteBuf encodeRoute(String route) { return TaggingMetadataCodec.createTaggingContent( ByteBufAllocator.DEFAULT, Collections.singletonList(route)); } 2. RequestResponse
服务端处理函数
在这里我们编写一个简单的 Handler，它的 Route 是 test.echo，它接收一个请求并返回请求 Payload 的 data 中的字符串。
@MessageMapping("test.echo") public Mono<String> simplyEcho(String data) throws InterruptedException { Thread.sleep(1500); logger.info("[test.echo]Received echo string from client: {}", data); return Mono.just(String.format("[test.echo]I received your string: %s. Thank you.", data)); } 注意，这里的参数也可以是 Mono<String> ，然后对 Mono 进行操作并返回。事实上，如果严格按照响应式编程的策略，这里应该直接对 Mono 进行操作。
客户端发送请求
- 生成 metadata 的 route 信息，然后将字符串和 metadata 放入 Payload
ByteBuf routeMetadata = encodeRoute("test.echo"); Payload echoPayload = ByteBufPayload.create( ByteBufUtil.writeUtf8(ByteBufAllocator.DEFAULT, "This is a message from client using rsocket-java library."), routeMetadata); - 新建一个 RequestResponse，并对这次请求做一些设置；可以看到 RequestResponse 方法返回的数据类型是
Mono<Payload>。然后我们对这个 Mono 设定一些操作（具体操作请看代码注释）：
Mono<Payload> requestResponse = socket.requestResponse(echoPayload); requestResponse // 当 subscribe() 操作开始执行时打印一下日志 .doOnSubscribe(subscription -> logger.info("Test1 subscribed to {}", subscription.toString())) // 当携带的请求成功后要做的事情 .doOnSuccess(payload -> { logger.info("Test1 - Successfully returned: {}", payload.getDataUtf8()); payload.release(); }) .doOnError(throwable -> logger.info("Test1 doOnError: {}", throwable.toString())) // 可以使用 timeout 丢弃等待超时的 Mono //.timeout(Duration.ofSeconds(1)) // 可以使用 doOnTerminate 在请求结束后做一些工作 // .doOnTerminate(() -> {}) // 但是一定要设置 doOnError //.doOnError(TimeoutException.class, e -> logger.info("Test1 doOnError: {}", e.toString())) // .onErrorReturn(TimeoutException.class, DefaultPayload.create("Payload: Test1 - timeout")) // 可以使用 log() 来观察数据的状态 //.log() // 客户端在执行 subscribe() 操作时才会开始从服务端接收数据流 // 在响应式编程中使用 subscribe 操作符是订阅一个数据流并处理发布的数据、错误和完成信号的核心方式之一 .subscribe(); 请求发出后主线程不会阻塞，所以我们需要使用 socket.onClose().block(); 保持连接。
然后我们尝试运行服务端和客户端，看看一看客户端的输出：
[main] INFO org.example.RSocketClientRaw - My UUID is 0718ef3b-9ee0-42f1-9003-700a8aa9a98d [main] INFO org.example.RSocketClientRaw - Test1 subscribed to RequestResponseRequesterMono [reactor-tcp-epoll-2] INFO org.example.RSocketClientRaw - Test1 - Successfully returned: [test.echo]I received your string: This is a message from client using rsocket-java library.. Thank you. 服务端日志：
2023-03-12 21:47:29.291 INFO 32099 --- [or-http-epoll-2] o.example.controller.RSocketController : [connect.setup]Client connection: 0718ef3b-9ee0-42f1-9003-700a8aa9a98d 2023-03-12 21:47:32.304 INFO 32099 --- [or-http-epoll-2] o.example.controller.RSocketController : [test.echo]Received echo string from client: This is a message from client using rsocket-java library. 客户端成功地发出请求并收到来自服务端的回复。
3. FireAndForget
服务端
@MessageMapping("upload.log") public void fireAndForgetHandler(@Headers Map<String, Object> header, RSocketRequester requester, String data) { header.forEach((k, v) -> System.out.printf("[upload.log]header key: %s, val: %sn", k, v)); System.out.printf("[upload.log]UploadEventLogs: Received log string from client: %sn", data); } 服务端接受一个请求，不返回任何结果（Fire'n'Forget），只在服务端打印 Header 的内容。
客户端
// 测试 FnF routeMetadata = TaggingMetadataCodec.createTaggingContent(ByteBufAllocator.DEFAULT, Collections.singletonList("upload.log")); socket.fireAndForget( ByteBufPayload.create( ByteBufUtil.writeUtf8(ByteBufAllocator.DEFAULT, "This is a log from client using rsocket-java library."), routeMetadata)) .doOnSubscribe(subscription -> logger.info("Test2 - Fire And Forget onSubscribe: {}", subscription.toString())) .subscribe(); 客户端输出：
[main] INFO org.example.RSocketClientRaw - Test2 - Fire And Forget onSubscribe: FireAndForgetRequesterMono 服务端输出：
2023-03-10 15:10:25.675 INFO 5318 --- [or-http-epoll-4] o.example.controller.RSocketController : [test.echo]Received echo string from client: This is a message from client using rsocket-java library. [upload.log]header key: dataBufferFactory, val: NettyDataBufferFactory (PooledByteBufAllocator(directByDefault: true)) [upload.log]header key: rsocketRequester, val: org.springframework.messaging.rsocket.DefaultRSocketRequester@607cc59 [upload.log]header key: lookupDestination, val: upload.log [upload.log]header key: contentType, val: application/binary [upload.log]header key: rsocketFrameType, val: REQUEST_FNF [upload.log]UploadEventLogs: Received log string from client: This is a log from client using rsocket-java library. 4. RequestStream
服务端
服务端接收一个 Mono<String> 然后返回给客户端包含 10 个 String 的 Flux。
事实上，严格按照响应式编程的策略，这里应该直接对 Mono 进行操作，可以使用 flatMapMany() 把生成的数据流通过异步方式处理，扩展出新的数据流。下面是扩展新数据流的简单示例：
Mono.just(3) .flatMapMany(i -> Flux.range(0, i)) .subscribe(System.out::println); 在这里为了演示方便就先打印 Mono 然后新生成一个 Flux。
@MessageMapping("handler.request.stream") public Flux<String> responseStreaming(Mono<String> request) { request .doOnNext(s -> logger.info("[handler.request.stream]: {}", s)) // 可以使用 then() 结束操作链 .then() .subscribe(); return Flux .range(1, 10) .map(idx -> String.format("Resp from Server: %s, Thank you!", idx)); } 客户端
请看代码注释来理解对数据流 Flux 的各种操作：
// 测试 RequestStream routeMetadata = encodeRoute("handler.request.stream"); Flux<Payload> requestStream = socket.requestStream( ByteBufPayload.create( ByteBufUtil.writeUtf8(ByteBufAllocator.DEFAULT, "TEST3 - Request&Stream"), routeMetadata)); requestStream // 当然可以使用 map 对每个 Payload 进行操作，这会改变数据 // .map(payload -> System.out.printf("%sn", payload.getDataUtf8())) .doOnSubscribe(subscription -> logger.info("Test3 subscribed to {}", subscription.toString())) // 使用 doOnNext 不会对流的数据进行改变 // doOnNext()是一个 Reactor 式流操作符，它允许编写者注册一个在每次出现新元素时执行的回调函数 .doOnNext(nextPayload -> System.out.println("Test3 Received payload: " + nextPayload.getDataUtf8())) // 当需要从流中选择一些特定的元素时，可以使用 Flux.take(long n) 操作符 // 该操作符将创建一个新的 Flux，该 Flux 包含原始 Flux 的前 n 个元素 // take 操作符发出了指定数量的元素之后，就不再接收任何元素，并且将取消其上游发布者的订阅 // 在这里服务端使用 Flux.range 来限定 Flux 流中的元素个数 // 如果服务端使用 Flux.interval 生成一个无限长度的流，客户端使用 take 接收限定个数的元素 // 便会取消发布者的订阅 .take(5) .subscribe(); 客户端输出结果：
[main] INFO org.example.RSocketClientRaw - My UUID is 28afc749-75e1-4289-8607-14810103de6c [main] INFO org.example.RSocketClientRaw - Test3 subscribed to RequestStreamRequesterFlux Test3 Received payload: Resp from Server: 1, Thank you! Test3 Received payload: Resp from Server: 2, Thank you! Test3 Received payload: Resp from Server: 3, Thank you! Test3 Received payload: Resp from Server: 4, Thank you! Test3 Received payload: Resp from Server: 5, Thank you! 服务端接收到了请求：
2023-03-12 22:01:33.520 INFO 32099 --- [or-http-epoll-3] o.example.controller.RSocketController : [handler.request.stream]: TEST3 - Request&Stream 5. Channel
服务端
服务端接收来自客户端的整数字符串，将它们乘以2以后发送回去。我们不妨把处理客户端请求流的函数封装为一个 Spring Service：
@Service public class MathService { public Flux<String> doubleInteger(Flux<String> request) { return request .map(s -> { System.out.println("received " + s); int i = Integer.parseInt(s); return String.valueOf(i * 2); }); } } 编写处理函数：
@Autowired private MathService mathService; @MessageMapping("handler.request.channel") public Flux<String> responseChannel(Flux<String> payloads) { return this.mathService.doubleInteger(payloads); } 客户端
Flux<Payload> payloadFlux = Flux.range(-5, 10) .delayElements(Duration.ofMillis(500)) .map(obj -> { ByteBuf metadata = encodeRoute("handler.request.channel"); return ByteBufPayload.create( ByteBufUtil.writeUtf8(ByteBufAllocator.DEFAULT, obj.toString()), metadata); }); Flux<Payload> channelResp = socket.requestChannel(payloadFlux); channelResp .doOnSubscribe(subscription -> logger.info("Test4 subscribed to {}", subscription.toString())) .doOnError(throwable -> logger.info(throwable.toString())) .doOnNext(nextPayload -> System.out.println("Test4 Received payload: " + nextPayload.getDataUtf8())) .subscribe(); 客户端输出：
[main] INFO org.example.RSocketClientRaw - My UUID is 96ff8fe7-416c-4607-9518-463114725a7a [main] INFO org.example.RSocketClientRaw - Test4 subscribed to RequestChannelRequesterFlux Test4 Received payload: -10 Test4 Received payload: -8 Test4 Received payload: -6 Test4 Received payload: -4 Test4 Received payload: -2 Test4 Received payload: 0 Test4 Received payload: 2 Test4 Received payload: 4 Test4 Received payload: 6 Test4 Received payload: 8 服务端输出：
2023-03-12 22:07:05.542 INFO 33083 --- [or-http-epoll-2] o.example.controller.RSocketController : [connect.setup]Client connection: 96ff8fe7-416c-4607-9518-463114725a7a received -5 received -4 received -3 received -2 received -1 received 0 received 1 received 2 received 3 received 4 下一篇文章会展示服务端如何主动调用客户端的函数。如有错误欢迎在评论区批评指正！
