I'm calling a Spring Data Rest URL using Spring Integration with an <int-http:outbound-gateway>.
My invocation is a simple HTTP GET towards a known resource URL (in my case, "examples").
This is the configuration of the <int-http:outbound-gateway>:
<int-http:outbound-gateway id="internalGW" request-channel="dataRestChannel"
encode-uri="true" url-expression="payload"
http-method="GET" extract-request-payload="true"
header-mapper="headerMapper">
</int-http:outbound-gateway>
In the logs I can see this message:
The 'extractPayload' attribute has no relevance for the current request since the HTTP Method is 'GET', and no request body will be sent for that method.
I suppose that is refered to the http-method="GET" extract-request-payload="true" configuration, but I don't know if this warning is relevant for the question.
This is the invocation of that outbound channel with a message that contains the REST url to be invoked:
public Object invokeUrl(String url){
MessagingChannel messagingChannel = (MessagingChannel)ApplicationContextResolver.getApplicationContext().getBean("requestChannelBean");
MessageChannel dataRestChannel = messagingChannel.getDataRestChannel();
MessagingTemplate messagingTemplate = new MessagingTemplate();
Message<?> requestMessage = MessageBuilder.withPayload(url).build();
Message<?> response = messagingTemplate.sendAndReceive(dataRestChannel, requestMessage);
return response.getPayload();
}
The invocation is fine, I have an HTTP status code 200; this is the response.getPayload():
<200 OK,
{
Server=[Apache-Coyote/1.1],
Cache-Control=[no-cache,no-store,max-age=0,must-revalidate],
Pragma=[no-cache],
Expires=[0],
X-XSS-Protection=[1; mode=block],
X-Frame-Options=[DENY,DENY],
X-Content-Type-Options=[nosniff,nosniff],
Transfer-Encoding=[chunked],
Date=[Fri,22 Jul 2016 13:03:22 GMT],
Content-Type=[application/hal+json],
Content-Length=[0]
}>
However, I don't understand why the "payload body" is empty, as you can see in the Content-Length header.
response GenericMessage<T> (id=219)
headers MessageHeaders (id=221)
payload ResponseEntity<T> (id=222)
body null
headers HttpHeaders (id=224)
statusCode HttpStatus (id=159)
If I go directly to that URL with a GET on the browser, this is the response that I receive:
{
"_embedded": {
"examples": []
},
"_links": {
"self": {
"href": "http://localhost:8080/restapp/api/examples"
},
"profile": {
"href": "http://localhost:8080/restapp/api/profile/examples"
}
}
}
I would expected this as the response payload, not an empty payload.
It seems that the ResponseEntity.body that I receive is empty.
Is there any way to get the same JSON result of the HTTP get with the outbound-gateway?
Thanks in advance.
UPDATE
As from Gary suggestion, I have monitored the traffic.
Here there are the details of the requests:
Spring Integration Request:
GET http://localhost:8080/restapp/api/examples HTTP/1.1
Host: localhost:8080
Connection: keep-alive
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Encoding: gzip, deflate, sdch
Accept-Language: it-IT,it;q=0.8,en-US;q=0.6,en;q=0.4
Browser Request:
GET http://localhost:8080/restapp/api/examples HTTP/1.1
Host: localhost:8080
Connection: keep-alive
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Encoding: gzip, deflate, sdch
Accept-Language: it-IT,it;q=0.8,en-US;q=0.6,en;q=0.4
Cookie: JSESSIONID=C966FB7DB6B172D530D7C1F4DC57C6B8
The requests seems to be the same, except for one header (the Cookie JSESSIONID, there is absent in Integration context).
UPDATE 2
Maybe I have found the reason of the empty payload on the response.
The "extractData" method of org.springframework.web.client.RestTemplate has the object instance this.delegate setted to a null value.
So, in return there is a ResponseEntity object without the body.
@Override
public ResponseEntity<T> extractData(ClientHttpResponse response) throws IOException {
if (this.delegate != null) { // this.delegate is null
T body = this.delegate.extractData(response);
return new ResponseEntity<T>(body, response.getHeaders(), response.getStatusCode());
}
else {
return new ResponseEntity<T>(response.getHeaders(), response.getStatusCode()); // <- it's executed this one
}
}
It would be interesting to discover why this.delegate is setted to null.
