int-http:inbound-gateway do not sets content-type header [INT-3697]

[spring-operator]

Alexei Osipov opened INT-3697 and commented

Almost same issue as in #7474.

Default behavior of int-http:inbound-gateway does not recognizes integration header "contentType" and tries to look up "Content-type".

So DefaultHttpHeaderMapper.inboundMapper().fromHeaders(...) just skips MessageHeaders.CONTENT_TYPE header.

---

Affects: 4.1.2, 4.1.3

Referenced from: pull request #1419

[spring-operator]

Alexei Osipov commented

Test case:

@Test
    public void testFromHeaders() {
        Map<String, Object> map = new HashMap<>();
        map.put(MessageHeaders.CONTENT_TYPE, "abc");
        MessageHeaders messageHeaders = new MessageHeaders(map);
        HttpHeaders httpHeaders = new HttpHeaders();
        
        DefaultHttpHeaderMapper.inboundMapper().fromHeaders(messageHeaders, httpHeaders);
        
        Assert.assertTrue(httpHeaders.containsKey("Content-Type"));
    }

[spring-operator]

Artem Bilan commented

Alexei,

DefaultHttpHeaderMapper.inboundMapper() is for inbound HTTP Requests, so it isn't intended to get deal with non-standard HTTP headers.

If you mean the response part, then we rely there on the Accept request HTTP header.
And there is a code on the matter:

if (CollectionUtils.isEmpty(acceptTypes)) {
	acceptTypes = Collections.singletonList(MediaType.ALL);
}
for (HttpMessageConverter converter : this.getMessageConverters()) {
	for (MediaType acceptType : acceptTypes) {
		if (converter.canWrite(content.getClass(), acceptType)) {
			converter.write(content, acceptType, response);
			return;
		}
	}
}

Where the appropriate HttpMessageConverter populates correct Content-Type response header.

Please, share your specific case, where you really need the contentType from integration flow and when HttpMessageConverter logic isn't fit for you.

Thank you!

[spring-operator]

Alexei Osipov commented

Yes, I mean processing of response for an inbound HTTP request.

Case:
We use a pair of int-http:inbound-gateway and int-http:outbound-gateway to proxy incoming requests to an external system. So we want to transfer a Content-Type from a reply of external service as is to a requesting service.

Flow:

1. request comes to inbound-gateway
2. inbound-gateway converts headers with DefaultHttpHeaderMapper#toHeaders(...) (Content-Type -> contentType)
3. outbound-gateway converts headers back with DefaultHttpHeaderMapper#fromHeaders(...) (contentType -> Content-Type)
4. outbound-gateway sends HTTP request to external service
5. external service processes request and generates response
6. outbound-gateway gets HTTP response from external service
7. outbound-gateway converts response headers with DefaultHttpHeaderMapper#toHeaders(...) (Content-Type -> contentType)
8. inbound-gateway converts response headers with DefaultHttpHeaderMapper#fromHeaders(...) (Expected: contentType -> Content-Type. Actual: header is lost)
9. inbound-gateway sends response to client

I agree that it's not really common case but the actual behavior is quite confusing for me.

[spring-operator]

Gary Russell commented

Merged to master.

Alexei_Osipov Unfortunately, we can't apply this change to the 4.1.x branch because it represents a behavior change. Although it's a bug, we can't afford the potential breakage of applications that expect the existing behavior.

With 4.2, we will be able to cover the behavior change in the 4.1 to 4.2 migration guide.

For 4.1, the work-around is to add a <header-enricher/> to copy the header as content-type.

[spring-operator]

Alexei Osipov commented

Artem, Gary, thank you!