Question

“您正在考虑的当务之急是，第一行将被执行，然后第二行将被执行，而在webflux中则并非如此。您必须考虑事件回调。”

我同意该评估（我有很多“当务之急”的经验），并希望人们可以帮助我进行方向校正，以了解我如何查看解决方案空间。我将发布三个具有相同“功能”的不同版本，但其中只有一个起作用（并且，我愿意就如何/应该修改该版本以更好地与响应/功能实现保持一致的方式发表评论。）

在进行报价评估的人员的指导/帮助下，我能够使`DemoPOJOHandler.add（ServerRequest）'正常工作。该代码以及调试级别的输出如下所示。我注意到的是，在 HTTP POST“ / v2 / DemoPOJO” 和*“ Mapped to mil.navy ...”行之后，有一个 reactor.netty条目。 channel.FluxReceive 说明“ 订阅入站接收器。”。这似乎是关键动作，而我的其他两次尝试都没有这样做。

我的具体问题（尽管是“长假”）是：

我“认为”将执行语句＃1，然后“语句＃2”等是解决方案空间的“必要”视图。但是，在下面的示例中，这似乎是正在发生的行为。 logger 语句在08：38：34.217执行，然后在08：38：34.251进行订阅，然后在08：39：34.267实例化DemoPOJO，然后一切正常。 / p>

但是， request.bodyToMono()... 序列中的链接看上去与命令式代码中的方法链接（例如，'Integer.toString（）。indexOf （）'），但lambda除外（或者，lambda的存在是“事物改变”的原因吗？）。因此，从理论上讲，如果 request.bodyToMono()... 序列不需要“ .then() ”或“ .switchIfEmpty() < / em>”，那么为什么核心 request.bodyToMono()... 序列不执行“ service.add(demoPOJO) ”？我知道没有订阅Mono，但是为什么订阅中需要链中的其他语句并将POJO添加到回购中？

此代码成功执行...

@Component public class DemoPOJOHandler { private Logger logger = LoggerFactory.getLogger(DemoPOJOHandler.class); @Autowired private DemoPOJOService service; public Mono<ServerResponse> add(ServerRequest request) { logger.debug("DemoPOJOHandler.add( ServerRequest )"); return request.bodyToMono(DemoPOJO.class).doOnSuccess(demoPOJO -> service.add(demoPOJO)) .then(ServerResponse.ok().build()) .switchIfEmpty(ServerResponse.badRequest() .contentType(MediaType.APPLICATION_JSON) .build()); } } 2019-07-25 08:38:34.144 DEBUG 11992 --- [ctor-http-nio-2] io.netty.buffer.AbstractByteBuf : -Dio.netty.buffer.checkAccessible: true 2019-07-25 08:38:34.145 DEBUG 11992 --- [ctor-http-nio-2] io.netty.buffer.AbstractByteBuf : -Dio.netty.buffer.checkBounds: true 2019-07-25 08:38:34.145 DEBUG 11992 --- [ctor-http-nio-2] i.n.util.ResourceLeakDetectorFactory : Loaded default ResourceLeakDetector: io.netty.util.ResourceLeakDetector@7a8a4d6a 2019-07-25 08:38:34.157 DEBUG 11992 --- [ctor-http-nio-2] r.n.http.server.HttpServerOperations : [id: 0xa2da3d98, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62644] New http connection, requesting read 2019-07-25 08:38:34.157 DEBUG 11992 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations : [id: 0x5f552130, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62645] New http connection, requesting read 2019-07-25 08:38:34.157 DEBUG 11992 --- [ctor-http-nio-3] reactor.netty.channel.BootstrapHandlers : [id: 0x5f552130, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62645] Initialized pipeline DefaultChannelPipeline{(BootstrapHandlers$BootstrapInitializerHandler#0 = reactor.netty.channel.BootstrapHandlers$BootstrapInitializerHandler), (reactor.left.httpCodec = io.netty.handler.codec.http.HttpServerCodec), (reactor.left.httpTrafficHandler = reactor.netty.http.server.HttpTrafficHandler), (reactor.right.reactiveBridge = reactor.netty.channel.ChannelOperationsHandler)} 2019-07-25 08:38:34.157 DEBUG 11992 --- [ctor-http-nio-2] reactor.netty.channel.BootstrapHandlers : [id: 0xa2da3d98, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62644] Initialized pipeline DefaultChannelPipeline{(BootstrapHandlers$BootstrapInitializerHandler#0 = reactor.netty.channel.BootstrapHandlers$BootstrapInitializerHandler), (reactor.left.httpCodec = io.netty.handler.codec.http.HttpServerCodec), (reactor.left.httpTrafficHandler = reactor.netty.http.server.HttpTrafficHandler), (reactor.right.reactiveBridge = reactor.netty.channel.ChannelOperationsHandler)} 2019-07-25 08:38:34.157 DEBUG 11992 --- [ctor-http-nio-3] io.netty.util.Recycler : -Dio.netty.recycler.maxCapacityPerThread: 4096 2019-07-25 08:38:34.157 DEBUG 11992 --- [ctor-http-nio-3] io.netty.util.Recycler : -Dio.netty.recycler.maxSharedCapacityFactor: 2 2019-07-25 08:38:34.157 DEBUG 11992 --- [ctor-http-nio-3] io.netty.util.Recycler : -Dio.netty.recycler.linkCapacity: 16 2019-07-25 08:38:34.157 DEBUG 11992 --- [ctor-http-nio-3] io.netty.util.Recycler : -Dio.netty.recycler.ratio: 8 2019-07-25 08:38:34.173 DEBUG 11992 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations : [id: 0x5f552130, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62645] Increasing pending responses, now 1 2019-07-25 08:38:34.173 DEBUG 11992 --- [ctor-http-nio-3] reactor.netty.http.server.HttpServer : [id: 0x5f552130, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62645] Handler is being applied: org.springframework.http.server.reactive.ReactorHttpHandlerAdapter@579c20c6 2019-07-25 08:38:34.195 DEBUG 11992 --- [ctor-http-nio-3] o.s.w.s.adapter.HttpWebHandlerAdapter : [5f552130] HTTP POST "/v2/DemoPOJO" 2019-07-25 08:38:34.217 DEBUG 11992 --- [ctor-http-nio-3] o.s.w.r.f.s.s.RouterFunctionMapping : [5f552130] Mapped to mil.navy.demo.DemoPOJO.DemoPOJORouter$$Lambda$258/1123559518@22a8277c 2019-07-25 08:38:34.217 DEBUG 11992 --- [ctor-http-nio-3] mil.navy.demo.DemoPOJO.DemoPOJOHandler : DemoPOJOHandler.add( ServerRequest ) 2019-07-25 08:38:34.251 DEBUG 11992 --- [ctor-http-nio-3] reactor.netty.channel.FluxReceive : [id: 0x5f552130, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62645] Subscribing inbound receiver [pending: 0, cancelled:false, inboundDone: false] 2019-07-25 08:38:34.267 DEBUG 11992 --- [ctor-http-nio-3] mil.navy.demo.DemoPOJO.DemoPOJO : DemoPOJO.DemoPOJO( 666, foo_666, 10666 ) 2019-07-25 08:38:34.267 DEBUG 11992 --- [ctor-http-nio-3] mil.navy.demo.DemoPOJO.DemoPOJO : DemoPOJO.toString() 2019-07-25 08:38:34.267 DEBUG 11992 --- [ctor-http-nio-3] o.s.http.codec.json.Jackson2JsonDecoder : [5f552130] Decoded [666 :: foo_666 :: 10666] 2019-07-25 08:38:34.267 DEBUG 11992 --- [ctor-http-nio-3] mil.navy.demo.DemoPOJO.DemoPOJOService : DemoPOJOService.add( DemoPOJO ) 2019-07-25 08:38:34.267 DEBUG 11992 --- [ctor-http-nio-3] mil.navy.demo.DemoPOJO.DemoPOJORepo : DemoPOJORepo.add( DemoPOJO ) 2019-07-25 08:38:34.267 DEBUG 11992 --- [ctor-http-nio-3] mil.navy.demo.DemoPOJO.DemoPOJO : DemoPOJO.getId() 2019-07-25 08:38:34.267 DEBUG 11992 --- [ctor-http-nio-3] mil.navy.demo.DemoPOJO.DemoPOJO : DemoPOJO.getId() 2019-07-25 08:38:34.267 DEBUG 11992 --- [ctor-http-nio-3] mil.navy.demo.DemoPOJO.DemoPOJORepo : DemoPOJORepo.add( DemoPOJO ) -> adding for id 666 2019-07-25 08:38:34.267 DEBUG 11992 --- [ctor-http-nio-3] mil.navy.demo.DemoPOJO.DemoPOJO : DemoPOJO.getId() 2019-07-25 08:38:34.272 DEBUG 11992 --- [ctor-http-nio-3] o.s.w.s.adapter.HttpWebHandlerAdapter : [5f552130] Completed 200 OK 2019-07-25 08:38:34.273 DEBUG 11992 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations : [id: 0x5f552130, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62645] Last HTTP response frame 2019-07-25 08:38:34.273 DEBUG 11992 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations : [id: 0x5f552130, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62645] No sendHeaders() called before complete, sending zero-length header 2019-07-25 08:38:34.274 DEBUG 11992 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations : [id: 0x5f552130, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62645] Decreasing pending responses, now 0 2019-07-25 08:38:34.275 DEBUG 11992 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations : [id: 0x5f552130, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62645] Last HTTP packet was sent, terminating the channel 2019-07-25 08:38:41.720 DEBUG 11992 --- [169.254.211.161] sun.rmi.transport.tcp : RMI TCP Connection(4)-169.254.211.161: (port 62610) connection closed 2019-07-25 08:38:41.720 DEBUG 11992 --- [169.254.211.161] sun.rmi.transport.tcp : RMI TCP Connection(4)-169.254.211.161: close connection

此代码执行“无错误”，但从不进行订阅，因此也从不执行链的“ doOnSuccess(...) ”部分。但是，看起来应该吗？将单独的 return ... 语句链接到带有<< em> .then（）的'request.bodyToMono（...）'语句的“魔术”是什么？ ...）“？

@Component
public class DemoPOJOHandler {

    private Logger logger = LoggerFactory.getLogger(DemoPOJOHandler.class);

    @Autowired
    private DemoPOJOService service;

    public Mono<ServerResponse> add(ServerRequest request) {
        logger.debug("DemoPOJOHandler.add( ServerRequest )");

        request.bodyToMono(DemoPOJO.class).doOnSuccess(demoPOJO -> System.out.println("DEMO -> " + demoPOJO.toString()));
        return  ServerResponse.ok().build();
    }
}


2019-07-25 08:40:16.155 DEBUG 17064 --- [169.254.211.161] sun.rmi.transport.tcp                    : RMI TCP Connection(4)-169.254.211.161: (port 62661) connection closed
2019-07-25 08:40:16.155 DEBUG 17064 --- [169.254.211.161] sun.rmi.transport.tcp                    : RMI TCP Connection(4)-169.254.211.161: close connection
2019-07-25 08:40:18.248 DEBUG 17064 --- [ctor-http-nio-2] io.netty.buffer.AbstractByteBuf          : -Dio.netty.buffer.checkAccessible: true
2019-07-25 08:40:18.248 DEBUG 17064 --- [ctor-http-nio-2] io.netty.buffer.AbstractByteBuf          : -Dio.netty.buffer.checkBounds: true
2019-07-25 08:40:18.248 DEBUG 17064 --- [ctor-http-nio-2] i.n.util.ResourceLeakDetectorFactory     : Loaded default ResourceLeakDetector: io.netty.util.ResourceLeakDetector@3860465a
2019-07-25 08:40:18.266 DEBUG 17064 --- [ctor-http-nio-2] r.n.http.server.HttpServerOperations     : [id: 0x768a1f21, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62695] New http connection, requesting read
2019-07-25 08:40:18.266 DEBUG 17064 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations     : [id: 0x51900c31, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62696] New http connection, requesting read
2019-07-25 08:40:18.267 DEBUG 17064 --- [ctor-http-nio-3] reactor.netty.channel.BootstrapHandlers  : [id: 0x51900c31, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62696] Initialized pipeline DefaultChannelPipeline{(BootstrapHandlers$BootstrapInitializerHandler#0 = reactor.netty.channel.BootstrapHandlers$BootstrapInitializerHandler), (reactor.left.httpCodec = io.netty.handler.codec.http.HttpServerCodec), (reactor.left.httpTrafficHandler = reactor.netty.http.server.HttpTrafficHandler), (reactor.right.reactiveBridge = reactor.netty.channel.ChannelOperationsHandler)}
2019-07-25 08:40:18.267 DEBUG 17064 --- [ctor-http-nio-2] reactor.netty.channel.BootstrapHandlers  : [id: 0x768a1f21, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62695] Initialized pipeline DefaultChannelPipeline{(BootstrapHandlers$BootstrapInitializerHandler#0 = reactor.netty.channel.BootstrapHandlers$BootstrapInitializerHandler), (reactor.left.httpCodec = io.netty.handler.codec.http.HttpServerCodec), (reactor.left.httpTrafficHandler = reactor.netty.http.server.HttpTrafficHandler), (reactor.right.reactiveBridge = reactor.netty.channel.ChannelOperationsHandler)}
2019-07-25 08:40:18.273 DEBUG 17064 --- [ctor-http-nio-3] io.netty.util.Recycler                   : -Dio.netty.recycler.maxCapacityPerThread: 4096
2019-07-25 08:40:18.273 DEBUG 17064 --- [ctor-http-nio-3] io.netty.util.Recycler                   : -Dio.netty.recycler.maxSharedCapacityFactor: 2
2019-07-25 08:40:18.273 DEBUG 17064 --- [ctor-http-nio-3] io.netty.util.Recycler                   : -Dio.netty.recycler.linkCapacity: 16
2019-07-25 08:40:18.273 DEBUG 17064 --- [ctor-http-nio-3] io.netty.util.Recycler                   : -Dio.netty.recycler.ratio: 8
2019-07-25 08:40:18.285 DEBUG 17064 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations     : [id: 0x51900c31, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62696] Increasing pending responses, now 1
2019-07-25 08:40:18.289 DEBUG 17064 --- [ctor-http-nio-3] reactor.netty.http.server.HttpServer     : [id: 0x51900c31, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62696] Handler is being applied: org.springframework.http.server.reactive.ReactorHttpHandlerAdapter@7fa4fcbc
2019-07-25 08:40:18.297 DEBUG 17064 --- [ctor-http-nio-3] o.s.w.s.adapter.HttpWebHandlerAdapter    : [51900c31] HTTP POST "/v2/DemoPOJO"
2019-07-25 08:40:18.315 DEBUG 17064 --- [ctor-http-nio-3] o.s.w.r.f.s.s.RouterFunctionMapping      : [51900c31] Mapped to mil.navy.demo.DemoPOJO.DemoPOJORouter$$Lambda$262/1446001495@27a07cfc
2019-07-25 08:40:18.316 DEBUG 17064 --- [ctor-http-nio-3] mil.navy.demo.DemoPOJO.DemoPOJOHandler   : DemoPOJOHandler.add( ServerRequest )
2019-07-25 08:40:18.358 DEBUG 17064 --- [ctor-http-nio-3] o.s.w.s.adapter.HttpWebHandlerAdapter    : [51900c31] Completed 200 OK
2019-07-25 08:40:18.359 DEBUG 17064 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations     : [id: 0x51900c31, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62696] Last HTTP response frame
2019-07-25 08:40:18.359 DEBUG 17064 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations     : [id: 0x51900c31, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62696] No sendHeaders() called before complete, sending zero-length header
2019-07-25 08:40:18.360 DEBUG 17064 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations     : [id: 0x51900c31, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62696] Decreasing pending responses, now 0
2019-07-25 08:40:18.361 DEBUG 17064 --- [ctor-http-nio-3] r.n.http.server.HttpServerOperations     : [id: 0x51900c31, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62696] Last HTTP packet was sent, terminating the channel
2019-07-25 08:40:18.366 DEBUG 17064 --- [ctor-http-nio-3] r.n.channel.ChannelOperationsHandler     : [id: 0x51900c31, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:62696] No ChannelOperation attached. Dropping: 
         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 7b 0a 20 20 20 20 22 69 64 22 3a 20 36 36 36 2c |{.    "id": 666,|
|00000010| 0a 20 20 20 20 22 6e 61 6d 65 22 3a 20 22 66 6f |.    "name": "fo|
|00000020| 6f 5f 36 36 36 22 2c 0a 20 20 20 20 22 76 61 6c |o_666",.    "val|
|00000030| 75 65 22 3a 20 31 30 36 36 36 0a 7d             |ue": 10666.}    |
+--------+-------------------------------------------------+----------------+

此代码仅与NPE一起炸毁。我失败的逻辑是“好吧，如果没有发生 doOnSuccess（...）”是因为没有订阅 Mono ，那么就“订阅”了。并不是解决方案。在我看来，“为什么？”不那么明显。

@Component
public class DemoPOJOHandler {

    private Logger logger = LoggerFactory.getLogger(DemoPOJOHandler.class);

    @Autowired
    private DemoPOJOService service;

    public Mono<ServerResponse> add(ServerRequest request) {
        logger.debug("DemoPOJOHandler.add( ServerRequest )");

        request.bodyToMono(DemoPOJO.class).doOnSuccess(demoPOJO -> System.out.println("DEMO -> " + demoPOJO.toString()))
                                          .subscribe();
        return  ServerResponse.ok().build();
    }
}


reactor.core.Exceptions$ErrorCallbackNotImplemented: java.lang.NullPointerException
Caused by: java.lang.NullPointerException: null
at mil.navy.demo.DemoPOJO.DemoPOJOHandler.lambda$add$2(DemoPOJOHandler.java:73) ~[classes/:na]
at reactor.core.publisher.MonoPeekTerminal$MonoTerminalPeekSubscriber.onComplete(MonoPeekTerminal.java:311) [reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:1743) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:1743) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.MonoSingle$SingleSubscriber.onComplete(MonoSingle.java:155) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxFlatMap$FlatMapMain.checkTerminated(FluxFlatMap.java:794) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxFlatMap$FlatMapMain.drainLoop(FluxFlatMap.java:560) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxFlatMap$FlatMapMain.drain(FluxFlatMap.java:540) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxFlatMap$FlatMapMain.onComplete(FluxFlatMap.java:426) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxFlatMap$FlatMapMain.checkTerminated(FluxFlatMap.java:794) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxFlatMap$FlatMapMain.drainLoop(FluxFlatMap.java:560) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxFlatMap$FlatMapMain.drain(FluxFlatMap.java:540) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxFlatMap$FlatMapMain.onComplete(FluxFlatMap.java:426) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.DrainUtils.postCompleteDrain(DrainUtils.java:131) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.DrainUtils.postComplete(DrainUtils.java:186) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxMapSignal$FluxMapSignalSubscriber.onComplete(FluxMapSignal.java:213) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:136) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxPeek$PeekSubscriber.onComplete(FluxPeek.java:252) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:136) ~[reactor-core-3.2.10.RELEASE.jar:3.2.10.RELEASE]
at reactor.netty.channel.FluxReceive.terminateReceiver(FluxReceive.java:390) ~[reactor-netty-0.8.9.RELEASE.jar:0.8.9.RELEASE]
at reactor.netty.channel.FluxReceive.drainReceiver(FluxReceive.java:197) ~[reactor-netty-0.8.9.RELEASE.jar:0.8.9.RELEASE]
at reactor.netty.channel.FluxReceive.onInboundComplete(FluxReceive.java:338) ~[reactor-netty-0.8.9.RELEASE.jar:0.8.9.RELEASE]
at reactor.netty.channel.ChannelOperations.onInboundComplete(ChannelOperations.java:350) [reactor-netty-0.8.9.RELEASE.jar:0.8.9.RELEASE]
at reactor.netty.channel.ChannelOperations.terminate(ChannelOperations.java:399) [reactor-netty-0.8.9.RELEASE.jar:0.8.9.RELEASE]
at reactor.netty.http.server.HttpServerOperations.cleanHandlerTerminate(HttpServerOperations.java:519) [reactor-netty-0.8.9.RELEASE.jar:0.8.9.RELEASE]
at reactor.netty.http.server.HttpTrafficHandler.operationComplete(HttpTrafficHandler.java:314) [reactor-netty-0.8.9.RELEASE.jar:0.8.9.RELEASE]

    (... lots of stuff deleted to fit posting constraints ...)

2019-07-25 10:44:43.212 DEBUG 10544 --- [ctor-http-nio-3] r.n.channel.ChannelOperationsHandler     : [id: 0xa62e89df, L:/0:0:0:0:0:0:0:1:8080 - R:/0:0:0:0:0:0:0:1:64515] No ChannelOperation attached. Dropping: 
         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 7b 0a 20 20 20 20 22 69 64 22 3a 20 36 36 36 2c |{.    "id": 666,|
|00000010| 0a 20 20 20 20 22 6e 61 6d 65 22 3a 20 22 66 6f |.    "name": "fo|
|00000020| 6f 5f 36 36 36 22 2c 0a 20 20 20 20 22 76 61 6c |o_666",.    "val|
|00000030| 75 65 22 3a 20 31 30 36 36 36 0a 7d             |ue": 10666.}    |
+--------+-------------------------------------------------+----------------+
2019-07-25 10:45:08.112 DEBUG 10544 --- [169.254.211.161] sun.rmi.transport.tcp                    : RMI TCP Connection(3)-169.254.211.161: (port 64485) connection closed
2019-07-25 10:45:08.112 DEBUG 10544 --- [169.254.211.161] sun.rmi.transport.tcp                    : RMI TCP Connection(3)-169.254.211.161: close connection

Answer 1

由于我是您在最上方引用的即时消息，我将尝试回答您的问题。

首先，我们需要谈论“非阻塞”。什么是“非阻塞”？非阻塞是基于事件的。底层服务器Netty不能为每个请求分配一个线程，而是可以处理事件链和事件队列。

因此，当有人订阅时，netty将建立一个基本的事件队列（某种），该事件队列的工作原理基本上是：

x <- y <- z

要获取x，我们需要解析y，但是要获取y，我们需要解析z。人们通常将这种类型的编程称为“功能”部分。

当人们开始使用响应式编程时，我看到的最常见的错误之一是他们不了解subscriber是调用client。您的spring应用程序是publisher，每个调用您服务的client是subscriber。

您永远不应订阅您的应用程序

您的发布应用程序为什么要订阅自己？当您以人们通常理解的方式进行解释时。

因此，让我们看一下您的示例，我将按照相反的顺序进行处理：

示例3：

public Mono<ServerResponse> add(ServerRequest request) {
    logger.debug("DemoPOJOHandler.add( ServerRequest )");

    request.bodyToMono(DemoPOJO.class).doOnSuccess(demoPOJO -> System.out.println("DEMO -> " + demoPOJO.toString()))
                                      .subscribe();
    return  ServerResponse.ok().build();
}

在这里，我们以命令式的方式输入方法，我们向其发送请求，ServerRequest是一个具体的对象，但是一旦您执行bodyToMono，您将返回一个Mono<DemoPOJO>，而这又是一个包裹着CompletableFuture，里面有一个计算（将主体放入请求中，并将其放入您的dto中）

计算完成后，Mono将进入success状态并触发链中的后续操作，因此doOnSuccess将被触发。完成doOnSuccess后，它将返回Mono<Void>。

doOnSuccess完成后，这就是您的问题subscribe。因此，您在这里所做的是，一旦有人将ServerRequest发布到您的应用程序中，Netty（服务器）将建立一个事件链，并且在此事件链中，应用程序将自行订阅。

在这里，链是由订阅它的应用程序完成的。因此，该应用程序是其自己的客户端。

示例2：

public Mono<ServerResponse> add(ServerRequest request) {
    logger.debug("DemoPOJOHandler.add( ServerRequest )");

    request.bodyToMono(DemoPOJO.class).doOnSuccess(demoPOJO -> System.out.println("DEMO -> " + demoPOJO.toString()));
    return  ServerResponse.ok().build();
}

在这里，我们与示例3相同，只是事件链建立后，请求被映射到DTO，然后我们在doOnSuccess中进行操作，但是链断开了。 doOnSuccess表示已完成，但之后没有任何监听。

因此，这里的事件链坏了，它是不完整的。在您订阅之前，什么都不会发生，但是由于链条已断开，没有人可以subscribe，因此什么也不会发生。

示例1：

public Mono<ServerResponse> add(ServerRequest request) {
    logger.debug("DemoPOJOHandler.add( ServerRequest )");

    return request.bodyToMono(DemoPOJO.class).doOnSuccess(demoPOJO -> service.add(demoPOJO))
                                             .then(ServerResponse.ok().build())
                                             .switchIfEmpty(ServerResponse.badRequest()
                                                                          .contentType(MediaType.APPLICATION_JSON)
                                                                          .build());
}

这里链条完整。某事物在发出信号，即发出某种信号，当某事物完成时，下一个事物将触发，然后是下一个，下一个和下一个。

主叫客户端发布数据，服务器建立事件链，链完成，以便客户端订阅客户端订阅，然后事件链启动并触发所有回调并返回数据。

Flux<T>和Mono<T>都是单子CompletableFuture<T>周围的包装器类。 Optional<T>和Stream<T>也是monad，并且monad来自函数世界，例如编程语言Haskell。了解它们的工作方式的一个好方法是了解有关monad的更多信息。

如果您想全面了解monads，我会无耻地插入我自己的文章：

Write a Monad, in Java, seriously?

我也很推荐Intro to reactive programming，我会仔细阅读所有示例。

在Spring Webflux中实现“有效”，但是我试图理解“为什么？”

1 个答案: