Accept header handling is inconsistent [SPR-16750]

[spring-projects-issues]

Petar Cvitanusic opened SPR-16750 and commented

The fix for #20798 is breaking a bunch of our tests. I do agree with the fix in #20798 that Spring returns a 200 when the base is the same. For example Accepting "application/json" but returning "application/msword" is totally valid.

We have a controller method that returns attachments that can be different content types. In some cases spring throws a 406, in others it produces a 200.

The controller method does not specify what it produces, rather we specify the Content-Type header for the ResponseEntity:

@RequestMapping(method = RequestMethod.GET, value = "...")
public ResponseEntity<...> getAttachment(HttpServletRequest request) {
    
}

 

Scenario:

1. Accept header is "application/json"
2. Content type returned is "image/png"
3. Spring throws a 406. This is correct.

 

1. Accept header is "application/json"
2. Content type returned is "image/jpeg"
3. Spring returns a 200. This seems wrong to me.

---

Affects: 5.0.3, 5.0.4, 5.0.5

Reference URL: #20798

[spring-projects-issues]

Brian Clozel commented

Hi Petar Cvitanusic

The fix in #20798 can be summarized like this: adding consumes/produces attribute to the mapping annotation means you wish Spring MVC to assist you wit content negotiation. If nothing is provided there, it means the developers decide to take full control and Spring MVC should not be in the business of overriding the choice made there. If a Content-Type is provided in the response entity, we should use that information to select the right message converter, but we should not override the decision made by the controller.

Given the use case you're describing, you should probably ask Spring MVC for the media types in the Accept header and decide yourself how your endpoint should behave. The MediaType class offers a lot of facilities for that, and you can throw HttpMediaTypeNotAcceptableException manually when it is required by your application.

If anything, it seems you're disagreeing with #20720 (and not #20798 which is about a side-effect of that first fix). If this is the case, I'm afraid this change has been done on purpose and this behavior is now by design. Let me know if I've missed anything in my analysis.

[spring-projects-issues]

Petar Cvitanusic commented

Thanks for the explanation Brian,

It does look like we missed a MediaType in one of our custom message converters handling attachments which explains the discrepancy I mentioned above between jpeg vs png.

The explanation makes sense to me, I think we can close this bug.

[spring-projects-issues]

Brian Clozel commented

Alright Petar Cvitanusic, thanks for your feedback!