从服务异常中检索Spring Integration中的消息

Question

I am developing a Restful API using Spring Integration and I am stuck retrieving messages when an exception raises from one of my services.

This is my app-context:

<int-http:inbound-gateway   id="v1.getEvent.inbound.gateway"
                            path="/ptgapi/{apiVersion}/clients/{clientId}/events/{eventId}"
                            supported-methods="GET"
                            request-channel="v1.getEvent.channel.input"
                            reply-channel="v1.getEvent.channel.output"
                            error-channel="v1.getEvent.channel.error"
                            convert-exceptions="true"
                            mapped-request-headers="HTTP_REQUEST_HEADERS,X-ptg-client-token,X-ptg-user-id,X-ptg-user-token,X-ptg-channel"
                            request-timeout="50000"
                            reply-timeout="50000">

    <int-http:header name="apiVersion" expression="#pathVariables.apiVersion"/>
    <int-http:header name="clientId" expression="#pathVariables.clientId"/>
    <int-http:header name="eventId" expression="#pathVariables.eventId"/>

</int-http:inbound-gateway>

<int:chain input-channel="v1.getEvent.channel.input" output-channel="v1.getEvent.channel.output" send-timeout="50000">

    <int:header-enricher>
        <int:error-channel ref="v1.getEvent.channel.error" />
    </int:header-enricher>

    <int:service-activator ref="v1.validation.service" method="validateRequest"/>
    <int:service-activator ref="v1.getEvent.service" method="getEvent"/>    
    <int:object-to-json-transformer/>

</int:chain>

<int:chain input-channel="v1.getEvent.channel.error" output-channel="v1.getEvent.channel.output">
    <int:transformer ref="errorUnwrapper" method="manageError" />
</int:chain>

My errorUnwrapper transformer is:

@MessageEndpoint public class ErrorUnwrapper {

@Transformer
public Message<?> manageError(Message<?> errorMessage) {

    Message<?> failedMessage = ((MessagingException) errorMessage.getPayload())
                                .getFailedMessage();

    Message<?> messageOut = MessageBuilder
                                .withPayload("")
                                .copyHeadersIfAbsent(failedMessage.getHeaders())
                                .setHeaderIfAbsent(HttpHeaders.STATUS_CODE, HttpStatus.ALREADY_REPORTED)
                                .build();
    return failedMessage;
}

}

The idea is assign the status error code in the transformer to inform the user but the info never reaches the client although I can confirm the return statements is reached in debug mode...

What's could be the problem here?

Thanks!

Answer 1

The problem is you are replying to the defunct replyChannel header from the failedMessage ; the gateway is waiting for a reply on the replyChannel header in the errorMessage.

You can simply use the errorMessage or, if you need other headers from the failedMessage, use copyHeaders(errorMessage.getHeaders()).copyHeadersIfAbsent(failedMessge.getHeaders()) .

This will retain the correct replyChannel.

In 3.0 (currently at milestone 2), we have added enhanced diagnostics to report this fairly common mistake (where a reply is sent to a defunct reply channel).