Java 异常：org.springframework.messaging.MessageDeliveryException:调度程序没有通道的订户

我有一个沙箱来探索SpringCloudStream中新添加的函数，但我在一个SpringCloudStream应用程序中使用函数和供应商时遇到了一个问题

在代码中，我使用了中描述的示例

首先，我在

application.yml

中添加了相应的

spring.cloud.stream.bindings

和

spring.cloud.stream.Function.definition

属性，以添加到项目

Function

。一切正常，我将消息发布到

my fun in

Kafka主题，应用程序执行函数并将结果发送到

my fun out

主题

然后我将

Supplier

添加到同一个项目中，并使用相应的

spring.cloud.stream.bindings

将

spring.cloud.stream.function.definition

值更新到

fun；sup

。奇怪的事情开始发生了。当我尝试启动应用程序时，收到以下错误：

2020-01-15 01:45:16.608 ERROR 10128 --- [oundedElastic-1] o.s.integration.handler.LoggingHandler   : org.springframework.messaging.MessageDeliveryException: Dispatcher has no subscribers for channel 'application.sup-out-0'.; nested exception is org.springframework.integration.MessageDispatchingException: Dispatcher has no subscribers, failedMessage=GenericMessage [payload=byte[20], headers={contentType=application/json, id=89301e00-b285-56e0-cb4d-8133555c8905, timestamp=1579045516603}], failedMessage=GenericMessage [payload=byte[20], headers={contentType=application/json, id=89301e00-b285-56e0-cb4d-8133555c8905, timestamp=1579045516603}]
    at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:77)
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:453)
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:403)
    at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:187)
    at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:166)
    at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:47)
    at org.springframework.messaging.core.AbstractMessageSendingTemplate.send(AbstractMessageSendingTemplate.java:109)
    at org.springframework.integration.router.AbstractMessageRouter.doSend(AbstractMessageRouter.java:206)
    at org.springframework.integration.router.AbstractMessageRouter.handleMessageInternal(AbstractMessageRouter.java:188)
    at org.springframework.integration.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:170)
    at org.springframework.integration.handler.AbstractMessageHandler.onNext(AbstractMessageHandler.java:219)
    at org.springframework.integration.handler.AbstractMessageHandler.onNext(AbstractMessageHandler.java:57)
    at org.springframework.integration.endpoint.ReactiveStreamsConsumer$DelegatingSubscriber.hookOnNext(ReactiveStreamsConsumer.java:165)
    at org.springframework.integration.endpoint.ReactiveStreamsConsumer$DelegatingSubscriber.hookOnNext(ReactiveStreamsConsumer.java:148)
    at reactor.core.publisher.BaseSubscriber.onNext(BaseSubscriber.java:160)
    at reactor.core.publisher.FluxDoFinally$DoFinallySubscriber.onNext(FluxDoFinally.java:123)
    at reactor.core.publisher.EmitterProcessor.drain(EmitterProcessor.java:426)
    at reactor.core.publisher.EmitterProcessor.onNext(EmitterProcessor.java:268)
    at reactor.core.publisher.FluxCreate$BufferAsyncSink.drain(FluxCreate.java:793)
    at reactor.core.publisher.FluxCreate$BufferAsyncSink.next(FluxCreate.java:718)
    at reactor.core.publisher.FluxCreate$SerializedSink.next(FluxCreate.java:153)
    at org.springframework.integration.channel.FluxMessageChannel.doSend(FluxMessageChannel.java:63)
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:453)
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:403)
    at org.springframework.integration.channel.FluxMessageChannel.lambda$subscribeTo$2(FluxMessageChannel.java:83)
    at reactor.core.publisher.FluxPeekFuseable$PeekFuseableSubscriber.onNext(FluxPeekFuseable.java:189)
    at reactor.core.publisher.FluxPublishOn$PublishOnSubscriber.runAsync(FluxPublishOn.java:398)
    at reactor.core.publisher.FluxPublishOn$PublishOnSubscriber.run(FluxPublishOn.java:484)
    at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:84)
    at reactor.core.scheduler.WorkerTask.call(WorkerTask.java:37)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: org.springframework.integration.MessageDispatchingException: Dispatcher has no subscribers, failedMessage=GenericMessage [payload=byte[20], headers={contentType=application/json, id=89301e00-b285-56e0-cb4d-8133555c8905, timestamp=1579045516603}]
    at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:139)
    at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:106)
    at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:73)
    ... 34 more

之后，我尝试了几件事：

将

spring.cloud.stream.function.definition

还原为

fun

（禁用

sup

bean绑定到外部目标）。应用程序启动，功能正常，供应商不工作。一切如期而至

将

spring.cloud.stream.function.definition

更改为

sup

（禁用

fun

bean绑定到外部目标）。应用程序启动，功能不工作，供应商工作（每秒向

my sup out

topic发送一条消息）。一切都如预期的那样

更新了

spring.cloud.stream.function.definition

value到

fun；sup

。应用程序未启动，收到相同的MessageDeliveryException

将

spring.cloud.stream.function.definition

值交换为

sup；乐趣

。应用程序已启动，供应商已工作，但功能不工作（未向

我的乐趣

主题发送消息）

最后一个问题比错误更让我困惑），所以现在我需要有人帮我解决问题

我是否在配置中遗漏了什么？为什么更改由

分隔的bean顺序spring.cloud.stream.function.definition中的code>导致不同的结果？

完整项目已上载到并添加到以下位置：

StreamApplication.java：

build.gradle.kts：

插件{
JAVA
}
group=“com.kaine”
version=“1.0-SNAPSHOT”
存储库{
mavenCentral（）
}
依赖关系{
实现（平台（“org.springframework.cloud:springcloud依赖项：Hoxton.SR1”））
实现（“org.springframework.cloud:springcloudstarterstreamkafka”）
实现（平台（“org.springframework.boot:springboot依赖项：2.2.2.RELEASE”））
}
配置{
sourceCompatibility=JavaVersion.VERSION\u 11
}

事实上，这是我们的文档中的一个问题，因为我相信我们为他的案例提供了一个反应性供应商的坏例子。问题是您的供应商处于无限阻塞循环中。它基本上永远不会回来。 因此，请将其更改为：

@Bean
public Supplier<Flux<String>> sup() {
    return () -> Flux.fromStream(Stream.generate(new Supplier<String>() {

        @Override
        public String get() {
            try {
                Thread.sleep(1000);
                return "Hello from Supplier";
            } catch (Exception e) {
                // ignore
            }
        }

    })).subscribeOn(Schedulers.elastic()).share();
}

@Bean
公共供应商支持（）{
return（）->Flux.fromStream（Stream.generate（newsupplier）（）{
@凌驾
公共字符串get（）{
试一试{
睡眠（1000）；
返回“供应商您好”；
}捕获（例外e）{
//忽略
}
}
})).subscribeOn（Schedulers.elastic（））.share（）；
}

Oleg，我试过你的代码片段，它真的解决了我的问题。谢谢你的建议）P.S.小提示：get方法需要

返回
在
try
/
catch
之后，否则编译器会大喊“缺少返回语句”@Oleg你能解释一下qestion中的代码被阻塞的原因吗？谢谢
spring:
  cloud:
    stream:
      function:
        definition: fun;sup
      bindings:
        fun-in-0:
          destination: my-fun-in
        fun-out-0:
          destination: my-fun-out
        sup-out-0:
          destination: my-sup-out

plugins {
    java
}

group = "com.kaine"
version = "1.0-SNAPSHOT"

repositories {
    mavenCentral()
}

dependencies {
        implementation(platform("org.springframework.cloud:spring-cloud-dependencies:Hoxton.SR1"))
        implementation("org.springframework.cloud:spring-cloud-starter-stream-kafka")

        implementation(platform("org.springframework.boot:spring-boot-dependencies:2.2.2.RELEASE"))
}

configure<JavaPluginConvention> {
    sourceCompatibility = JavaVersion.VERSION_11
}

@Bean
public Supplier<Flux<String>> sup() {
    return () -> Flux.fromStream(Stream.generate(new Supplier<String>() {

        @Override
        public String get() {
            try {
                Thread.sleep(1000);
                return "Hello from Supplier";
            } catch (Exception e) {
                // ignore
            }
        }

    })).subscribeOn(Schedulers.elastic()).share();
}