扩展 Flux/实现发布者并多次调用 s.onNext() 时，Spring 5 Reactive 失败

Question

我刚刚开始使用新的 Spring 5 响应式(Reactive)支持，并想模拟一些异步数据生成，注意到两个错误行为:

1) 多次调用 s.onNext( String ):

@GetMapping("/strings")
public Publisher<String> getStrings(){

    return new Publisher<String>() {

        @Override
        public void subscribe(Subscriber<? super String> s) {
            int i = 0;
            while(++i <= 5){
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                s.onNext("message");
            }
            s.onComplete();
        }
    };
}

在这种情况下，堆栈跟踪是:

2016-08-03 13:35:04.986 DEBUG 5136 --- [nio-8080-exec-1] s.w.r.r.m.a.RequestMappingHandlerMapping : Looking up handler method for path /strings
2016-08-03 13:35:04.994 DEBUG 5136 --- [nio-8080-exec-1] s.w.r.r.m.a.RequestMappingHandlerMapping : Returning handler method [public org.reactivestreams.Publisher<java.lang.String> com.codependent.spring5.playground.reactive.web.AccountsController.getStrings()]
2016-08-03 13:35:04.994 DEBUG 5136 --- [nio-8080-exec-1] o.s.b.f.s.DefaultListableBeanFactory     : Returning cached instance of singleton bean 'accountsController'
2016-08-03 13:35:07.120 DEBUG 5136 --- [nio-8080-exec-1] o.s.w.s.h.ExceptionHandlingWebHandler    : Could not complete request

java.lang.IllegalStateException: RECEIVED
    at org.springframework.http.server.reactive.AbstractResponseBodyProcessor$State.onNext(AbstractResponseBodyProcessor.java:316) ~[spring-web-5.0.0.M1.jar:5.0.0.M1]
    at org.springframework.http.server.reactive.AbstractResponseBodyProcessor.onNext(AbstractResponseBodyProcessor.java:77) ~[spring-web-5.0.0.M1.jar:5.0.0.M1]
    at org.springframework.http.server.reactive.AbstractResponseBodyProcessor.onNext(AbstractResponseBodyProcessor.java:47) ~[spring-web-5.0.0.M1.jar:5.0.0.M1]
    at org.springframework.http.server.reactive.ChannelSendOperator$WriteWithBarrier.doNext(ChannelSendOperator.java:97) ~[spring-web-5.0.0.M1.jar:5.0.0.M1]
    at reactor.core.publisher.OperatorAdapter.onNext(OperatorAdapter.java:88) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:123) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at com.codependent.spring5.playground.reactive.web.AccountsController$4.subscribe(AccountsController.java:107) [classes/:na]
    at reactor.core.publisher.FluxSource.subscribe(FluxSource.java:59) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxMap.subscribe(FluxMap.java:73) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at org.springframework.http.server.reactive.ChannelSendOperator.subscribe(ChannelSendOperator.java:54) [spring-web-5.0.0.M1.jar:5.0.0.M1]
    at reactor.core.publisher.MonoOtherwise.subscribe(MonoOtherwise.java:47) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply$MonoThenApplyManager.onNext(MonoThenApply.java:133) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.Operators$DeferredScalarSubscriber.complete(Operators.java:797) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply$MonoThenApplyManager$SecondSubscriber.onNext(MonoThenApply.java:203) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxResume$ResumeSubscriber.onNext(FluxResume.java:75) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:130) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:1293) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:186) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:1010) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxResume$ResumeSubscriber.onSubscribe(FluxResume.java:70) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onSubscribe(FluxMapFuseable.java:100) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxFlatMap.trySubscribeScalarMap(FluxFlatMap.java:169) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply.subscribe(MonoThenApply.java:51) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoMapFuseable.subscribe(MonoMapFuseable.java:69) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoOtherwise.subscribe(MonoOtherwise.java:47) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply$MonoThenApplyManager.onNext(MonoThenApply.java:133) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:71) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.drain(FluxConcatMap.java:383) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.onSubscribe(FluxConcatMap.java:192) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:96) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:60) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxConcatMap.subscribe(FluxConcatMap.java:116) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoNext.subscribe(MonoNext.java:45) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoOtherwiseIfEmpty.subscribe(MonoOtherwiseIfEmpty.java:47) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply.subscribe(MonoThenApply.java:58) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply.subscribe(MonoThenApply.java:58) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoOtherwise.subscribe(MonoOtherwise.java:47) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoOtherwise.subscribe(MonoOtherwise.java:47) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoOtherwise.subscribe(MonoOtherwise.java:47) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenSupply$MonoConcatIgnoreManager.drain(MonoThenSupply.java:167) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenSupply.subscribe(MonoThenSupply.java:55) [reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at org.springframework.http.server.reactive.ServletHttpHandlerAdapter.service(ServletHttpHandlerAdapter.java:93) [spring-web-5.0.0.M1.jar:5.0.0.M1]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:522) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:1110) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:785) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1425) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_45]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_45]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_45]

2016-08-03 13:35:07.121 DEBUG 5136 --- [nio-8080-exec-1] o.s.h.s.r.ServletServerHttpResponse      : Can't set the status 500 because the HTTP response has already been committed
2016-08-03 13:35:08.127 ERROR 5136 --- [nio-8080-exec-1] a.c.c.C.[.[.0.0.0.[.[httpHandlerServlet] : Servlet.service() for servlet [httpHandlerServlet] in context with path [] threw exception

reactor.core.Exceptions$BubblingException: java.lang.IllegalStateException: RECEIVED
    at reactor.core.Exceptions.bubble(Exceptions.java:97) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.Exceptions.onErrorDropped(Exceptions.java:263) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply$MonoThenApplyManager$SecondSubscriber.onError(MonoThenApply.java:209) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxResume$ResumeSubscriber.onError(FluxResume.java:105) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.OperatorAdapter.doOnSubscriberError(OperatorAdapter.java:113) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.OperatorAdapter.onNext(OperatorAdapter.java:91) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxMap$MapSubscriber.onNext(FluxMap.java:123) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at com.codependent.spring5.playground.reactive.web.AccountsController$4.subscribe(AccountsController.java:107) ~[classes/:na]
    at reactor.core.publisher.FluxSource.subscribe(FluxSource.java:59) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxMap.subscribe(FluxMap.java:73) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at org.springframework.http.server.reactive.ChannelSendOperator.subscribe(ChannelSendOperator.java:54) ~[spring-web-5.0.0.M1.jar:5.0.0.M1]
    at reactor.core.publisher.MonoOtherwise.subscribe(MonoOtherwise.java:47) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply$MonoThenApplyManager.onNext(MonoThenApply.java:133) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.Operators$DeferredScalarSubscriber.complete(Operators.java:797) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply$MonoThenApplyManager$SecondSubscriber.onNext(MonoThenApply.java:203) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxResume$ResumeSubscriber.onNext(FluxResume.java:75) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:130) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:1293) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.request(FluxMapFuseable.java:186) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:1010) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxResume$ResumeSubscriber.onSubscribe(FluxResume.java:70) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onSubscribe(FluxMapFuseable.java:100) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxFlatMap.trySubscribeScalarMap(FluxFlatMap.java:169) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply.subscribe(MonoThenApply.java:51) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoMapFuseable.subscribe(MonoMapFuseable.java:69) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoOtherwise.subscribe(MonoOtherwise.java:47) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply$MonoThenApplyManager.onNext(MonoThenApply.java:133) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:71) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:82) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.drain(FluxConcatMap.java:383) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.onSubscribe(FluxConcatMap.java:192) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:96) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:60) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.FluxConcatMap.subscribe(FluxConcatMap.java:116) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoNext.subscribe(MonoNext.java:45) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoOtherwiseIfEmpty.subscribe(MonoOtherwiseIfEmpty.java:47) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply.subscribe(MonoThenApply.java:58) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenApply.subscribe(MonoThenApply.java:58) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoOtherwise.subscribe(MonoOtherwise.java:47) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoOtherwise.subscribe(MonoOtherwise.java:47) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoOtherwise.subscribe(MonoOtherwise.java:47) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenSupply$MonoConcatIgnoreManager.drain(MonoThenSupply.java:167) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at reactor.core.publisher.MonoThenSupply.subscribe(MonoThenSupply.java:55) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    at org.springframework.http.server.reactive.ServletHttpHandlerAdapter.service(ServletHttpHandlerAdapter.java:93) ~[spring-web-5.0.0.M1.jar:5.0.0.M1]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) ~[tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) ~[tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:522) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:1110) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:785) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1425) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_45]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_45]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.4.jar:8.5.4]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_45]
Caused by: java.lang.IllegalStateException: RECEIVED
    at org.springframework.http.server.reactive.AbstractResponseBodyProcessor$State.onNext(AbstractResponseBodyProcessor.java:316) ~[spring-web-5.0.0.M1.jar:5.0.0.M1]
    at org.springframework.http.server.reactive.AbstractResponseBodyProcessor.onNext(AbstractResponseBodyProcessor.java:77) ~[spring-web-5.0.0.M1.jar:5.0.0.M1]
    at org.springframework.http.server.reactive.AbstractResponseBodyProcessor.onNext(AbstractResponseBodyProcessor.java:47) ~[spring-web-5.0.0.M1.jar:5.0.0.M1]
    at org.springframework.http.server.reactive.ChannelSendOperator$WriteWithBarrier.doNext(ChannelSendOperator.java:97) ~[spring-web-5.0.0.M1.jar:5.0.0.M1]
    at reactor.core.publisher.OperatorAdapter.onNext(OperatorAdapter.java:88) ~[reactor-core-3.0.0.BUILD-SNAPSHOT.jar:na]
    ... 57 common frames omitted

2) 多次调用 s.onNext( Alert.class -any DTO- ):

@GetMapping("/alerts")
public Publisher<Alert> getAlerts(){

    return new Publisher<Alert>() {

        @Override
        public void subscribe(Subscriber<? super Alert> s) {
            int i = 0;
            while(++i <= 5){
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                s.onNext(new Alert((long)1, "ms"));
            }
            s.onComplete();
        }
    };
}

现在它没有在日志上显示任何错误，但是 调用者获得 500 响应代码和内容 '[' .

日志:

2016-08-03 13:37:11.834 DEBUG 5136 --- [nio-8080-exec-3] o.s.web.reactive.DispatcherHandler       : Processing GET request for [http://localhost:8080/alerts]
2016-08-03 13:37:11.835 DEBUG 5136 --- [nio-8080-exec-3] s.w.r.r.m.a.RequestMappingHandlerMapping : Looking up handler method for path /alerts
2016-08-03 13:37:11.836 DEBUG 5136 --- [nio-8080-exec-3] s.w.r.r.m.a.RequestMappingHandlerMapping : Returning handler method [public org.reactivestreams.Publisher<com.codependent.spring5.playground.reactive.dto.Alert> com.codependent.spring5.playground.reactive.web.AccountsController.getAlerts()]
2016-08-03 13:37:11.836 DEBUG 5136 --- [nio-8080-exec-3] o.s.b.f.s.DefaultListableBeanFactory     : Returning cached instance of singleton bean 'accountsController'

为什么我们不能多次调用 onNext() ？我们怎么能那样做？

注意:我只要打电话 onNext一旦它工作正常:

@Override
public void subscribe(Subscriber<? super String> s) {
    s.onNext("my message" + Math.random());
    s.onComplete();
}

或者

@Override
public void subscribe(Subscriber<? super Alert> s) {
    s.onNext(new Alert((long)1, "ms"));
    s.onComplete();
}

Answer 1

我的 Publisher 实现没有遵循响应式(Reactive)流规范，这是我修复它的方式:

@GetMapping(value="/strings", produces="text/event-stream")
public Publisher<String> getStrings(){
    return new Publisher<String>() {

        private int loops = 5;

        @Override
        public void subscribe(Subscriber<? super String> s) {

            s.onSubscribe(new Subscription() {
                @Override
                public void request(long n) {
                    for (int i = 0; i < n; i++) {
                        if(loops-- > 0){
                            try {
                                Thread.sleep(1000);
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                            s.onNext("message"+Math.random());                          
                        }else{
                            s.onComplete();
                        }
                    }
                }
                @Override
                public void cancel() {
                    loops = 0;
                }
            });
        }
    };
}

如果您想了解更多相关信息，请查看 issue I opened in Spring's JIRA以及我得到的有用评论。