Spring 集成 "Publish Subscribe Channel" 与 Spring DSL

Question

我正在尝试构建一个简单的流程，我的流程开始于通过 HTTP 入站通道适配器接收 HTTP Post 请求并将其发布到 'SubscribableChannel'。可能有 'N' 数量的消费者订阅了该频道。下图为流程。

我正在尝试使用 Spring DSL 来配置此流程，但一直无法使其正常工作。下面是我的代码。

@Bean
public IntegrationFlow receiveHttpPost() {
    return IntegrationFlows.from(Http.inboundChannelAdapter("/receive")
            .mappedRequestHeaders("*")
            .requestChannel(httpInAdapterPubSubChannel()))
            .transform(new ObjectToStringTransformer())
            .get();
}

@Bean
public SubscribableChannel  httpInAdapterPubSubChannel()
{
    return MessageChannels.publishSubscribe("httpInAdapterPubSubChannel")
    .get();
}

@Bean
public IntegrationFlow subscriber1() {
    return IntegrationFlows.from(httpInAdapterPubSubChannel())
            .handle( message -> System.out.println("Enrich Headers based on Payload...."))
            .get();
}

@Bean
public IntegrationFlow subscriber2() {
     return IntegrationFlows.from(httpInAdapterPubSubChannel())
                .handle( message -> System.out.println("Save Payload to Audit Table..."))
                .get();
}

当我运行这个流程时，我得到 "Failed to handle Message; nested exception is org.springframework.messaging.core.DestinationResolutionException: no output-channel or replyChannel header available".

o.s.i.channel.PublishSubscribeChannel    : preSend on channel 'httpInAdapterPubSubChannel', message: GenericMessage [payload=Test, headers={content-length=4, http_requestMethod=POST, accept-language=en-US,en;q=0.8, accept=*/*, host=localhost:8080, http_requestUrl=http://localhost:8080/receive, connection=keep-alive, content-type=text/plain;charset=UTF-8, id=2c6ee729-96ee-1ae5-be31-a9bc56092758, cache-control=no-cache, accept-encoding=gzip, deflate, br, user-agent=Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36, timestamp=1484457726393}]
o.s.i.t.MessageTransformingHandler       : org.springframework.integration.transformer.MessageTransformingHandler#0 received message: GenericMessage [payload=Test, headers={content-length=4, http_requestMethod=POST, accept-language=en-US,en;q=0.8, accept=*/*, host=localhost:8080, http_requestUrl=http://localhost:8080/receive, connection=keep-alive, content-type=text/plain;charset=UTF-8, id=2c6ee729-96ee-1ae5-be31-a9bc56092758, cache-control=no-cache, accept-encoding=gzip, deflate, br, user-agent=Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36, timestamp=1484457726393}]
o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.messaging.MessagingException: Failed to handle Message; nested exception is org.springframework.messaging.core.DestinationResolutionException: no output-channel or replyChannel header available] with root cause

org.springframework.messaging.core.DestinationResolutionException: no output-channel or replyChannel header available
    at org.springframework.integration.handler.AbstractMessageProducingHandler.sendOutput(AbstractMessageProducingHandler.java:287) ~[spring-integration-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.integration.handler.AbstractMessageProducingHandler.produceOutput(AbstractMessageProducingHandler.java:212) ~[spring-integration-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.integration.handler.AbstractMessageProducingHandler.sendOutputs(AbstractMessageProducingHandler.java:129) ~[spring-integration-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.integration.handler.AbstractReplyProducingMessageHandler.handleMessageInternal(AbstractReplyProducingMessageHandler.java:115) ~[spring-integration-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.integration.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:127) ~[spring-integration-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.integration.dispatcher.BroadcastingDispatcher.invokeHandler(BroadcastingDispatcher.java:236) ~[spring-integration-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.integration.dispatcher.BroadcastingDispatcher.dispatch(BroadcastingDispatcher.java:185) ~[spring-integration-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:89) ~[spring-integration-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:423) ~[spring-integration-core-4.3.6.RELEASE.jar:4.3.6.RELEASE]
    at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:115) ~[spring-messaging-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:45) ~[spring-messaging-4.3.5.RELEASE.jar:4.3.5.RELEASE]

很明显我在这里做错了。我试图找到显示 "Publish Subscribe Channel" VIA Spring Integration DSL 或 Java Configuration 的示例。不幸的是，我找不到任何 :-/。如果有人能给我提供一个例子并帮助我找出我的流程有什么问题，我将不胜感激。

我的另一个观察结果是，"When I removed the Subscribers 'subscriber1' and 'subscriber2'"，我仍然遇到同样的错误。所以这意味着，我在配置 y HttpInboundAdapter 时做错了。

此外，如果我将 'httpInAdapterPubSubChannel' 切换为直接，并且只有一个路由流（没有分支），一切正常。

Answer 1

.transform(new ObjectToStringTransformer()) 正在尝试将结果发送到某个地方，但它不知道在哪里 - 入站适配器不期望回复并且转换器无处发送数据。

也许你的意思是这样的...

@Bean
public IntegrationFlow receiveHttpPost() {
    return IntegrationFlows.from(Http.inboundChannelAdapter("/receive")
        .mappedRequestHeaders("*"))
        .transform(new ObjectToStringTransformer())
        .channel(httpInAdapterPubSubChannel())
        .get();
}

即将转换器的结果发送到 pub/sub 通道。

DSL 参考有几个示例； here and here 例如。

Spring 集成 "Publish Subscribe Channel" 与 Spring DSL

Spring Integration "Publish Subscribe Channel" with Spring DSL

spring

spring-integration

publish-subscribe

spring-dsl