How to pass payload using HttpOutboundAdapter in Spring-Integration - https

Question

We are trying to pass a payload to a POST call that is being made using HttpOutboundGateway. A file is read and the content is stored in the channel. In order to retrieve the content of the channel, we are setting the extractPayload to true. We are using Spring-Integration along with DSL and not the XML approach. Any guidance would be appreciated.
return IntegrationFlows.from("FileContentChannel")
.channel("FileContentChannel")
.enrichHeaders(h -> h.header("xxx", "xxx")
.header("xxx", "xxx"))
.handle(Http.outboundGateway("http://payment/gateway")
.charset("UTF-8")
.httpMethod(HttpMethod.POST)
.extractPayload(true)
.mappedRequestHeaders("pay*")
.headerMapper(headerMapper())
.expectedResponseType(String.class))
.channel(MessageChannels.queue("paymentResponseChannel"))
.get();
Error log :
2016-10-26 16:34:22.343 ERROR 1584 --- [ask-scheduler-6] o.s.integration.handler.LoggingHandler : org.springframework.messaging.MessageHandlingException: HTTP request execution failed for URI [http://payment/gateway]; nested exception is org.springframework.web.client.HttpClientErrorException: 404 Not Found
at org.springframework.integration.http.outbound.HttpRequestExecutingMessageHandler.handleRequestMessage(HttpRequestExecutingMessageHandler.java:409)
at org.springframework.integration.handler.AbstractReplyProducingMessageHandler.handleMessageInternal(AbstractReplyProducingMessageHandler.java:109)
at org.springframework.integration.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:127)
at org.springframework.integration.dispatcher.AbstractDispatcher.tryOptimizedDispatch(AbstractDispatcher.java:116)
at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:148)
at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:121)
at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:77)
at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:423)
at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:373)
at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:115)
at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:45)
at org.springframework.messaging.core.AbstractMessageSendingTemplate.send(AbstractMessageSendingTemplate.java:105)
at org.springframework.integration.handler.AbstractMessageProducingHandler.sendOutput(AbstractMessageProducingHandler.java:292)
at org.springframework.integration.handler.AbstractMessageProducingHandler.produceOutput(AbstractMessageProducingHandler.java:212)
at org.springframework.integration.handler.AbstractMessageProducingHandler.sendOutputs(AbstractMessageProducingHandler.java:129)
at org.springframework.integration.handler.AbstractReplyProducingMessageHandler.handleMessageInternal(AbstractReplyProducingMessageHandler.java:115)
at org.springframework.integration.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:127)
at org.springframework.integration.endpoint.PollingConsumer.handleMessage(PollingConsumer.java:129)
at org.springframework.integration.endpoint.AbstractPollingEndpoint.doPoll(AbstractPollingEndpoint.java:272)
at org.springframework.integration.endpoint.AbstractPollingEndpoint.access$000(AbstractPollingEndpoint.java:58)
at org.springframework.integration.endpoint.AbstractPollingEndpoint$1.call(AbstractPollingEndpoint.java:190)
at org.springframework.integration.endpoint.AbstractPollingEndpoint$1.call(AbstractPollingEndpoint.java:186)
at org.springframework.integration.endpoint.AbstractPollingEndpoint$Poller$1.run(AbstractPollingEndpoint.java:353)
at org.springframework.integration.util.ErrorHandlingTaskExecutor$1.run(ErrorHandlingTaskExecutor.java:55)
at org.springframework.core.task.SyncTaskExecutor.execute(SyncTaskExecutor.java:50)
at org.springframework.integration.util.ErrorHandlingTaskExecutor.execute(ErrorHandlingTaskExecutor.java:51)
at org.springframework.integration.endpoint.AbstractPollingEndpoint$Poller.run(AbstractPollingEndpoint.java:344)
at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54)
at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:81)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(Unknown Source)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: org.springframework.web.client.HttpClientErrorException: 404 Not Found
at org.springframework.web.client.DefaultResponseErrorHandler.handleError(DefaultResponseErrorHandler.java:91)
at org.springframework.web.client.RestTemplate.handleResponse(RestTemplate.java:667)
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:620)
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:595)
at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:516)
at org.springframework.integration.http.outbound.HttpRequestExecutingMessageHandler.handleRequestMessage(HttpRequestExecutingMessageHandler.java:382)
... 35 more

Answer 1

The .handle() is for Service Activator EI pattern. And exactly its responsibility to deliver payload from the input channel to the target service. In your case it is RestTemplate underneath and an HTTP body is built from the payload.
Your configuration looks fully correct. I don't understand where is the problem...
EDIT
Caused by: org.springframework.web.client.HttpClientErrorException: 404 Not Found
Not, sure what makes you think that there is something wrong with payload. Looks like you are missing some HTTP header or use them with wrong value.
You should consult with the server to determine what should be done else.
There is no any clue in your StackTrace that there is something wrong with payload.
OTOH, since we get 404 Not Found that means that the payload is passed from the channel to the Http.outboundGateway().