HATEOAS: ResponseEntity<Resource> from @ExceptionHandler method not converted to HAL

[mvitz]

Given a controller like https://github.com/mvitz/spring-boot-hateoas-autoconfiguration-bug/blob/master/src/main/java/de/mvitz/spring/hateoas/server/ExceptionController.java with a @ExceptionHandler annotated method the response is not converted to valid HAL, see:

curl -i localhost:8080/exception -HAccept:application/hal+json
HTTP/1.1 400
Content-Type: application/hal+json;charset=UTF-8
Transfer-Encoding: chunked
Date: Thu, 02 Feb 2017 00:05:02 GMT
Connection: close

{"links":[{"rel":"self","href":"http://google.de"}],"message":"Foo"}

Maybe I am (again) missing some little thing here but I think given the example controller I should expect to receive a response with valid HAL.

Issue occurs with Spring-Boot 1.4.4.RELEASE and 1.5.1.RELEASE as well.

[bclozel]

I'm not sure this is supported by Spring HATOAS in the first, nor that representing an exception instance as a HAL resource makes sense. As far as I know, Boot does nothing special in that area.

Could you open this issue against the original project? (actually, is this a duplicate?)
Thanks!

[snicoll]

@mvitz I second that, please consider creating an issue in the original project first unless you have a strong indication that this is auto-configuration related.

[mvitz]

@snicoll for me (and I would consider myself as an advanced spring user) it's not always obvious which component is responsible for such stuff.

As a user I would expect that if I use the HATEOAS auto configuration and HAL is working from controller methods it works in an exception handler method as well. I never expected that this issue would be outside of configuration.

Using HATEOAS without Boot requires me to Annotate some Configuration with @EnableHypermedia and after that everything works. How am I supposed to not think this has something to do with auto configuration.

@blcozel
I had the same thought "does it make sense" but I think that should be the decision of the applications developer

I'm sorry if I cause additional work for this team but I think you should see this as a positive thing. I'm trying to help and improve your work and do not stop using it silently. Additionally I would like to thank you for all the good work.

[snicoll]

We obviously see your (and any report in genral) as a positive thing. But it isn't obvious from your report that this is working without Spring Boot. Actually you've done all that work but you didn't mention it!

[bclozel]

@mvitz

Using HATEOAS without Boot requires me to Annotate some Configuration with @EnableHypermedia and after that everything works.

Do you mean that you got this very use case to work when using the @EnableHypermedia annotation? In that case, @snicoll is right, this could be indeed a Spring Boot issue.

[mvitz]

Yes. If I add @EnableHypermedia this use case works. After some digging it this works because with the annotation the main Jackson object mapper is changed. With only the autoconfiguration present an additional mapper is created.

[wilkinsona]

I've reproduced the problem, and also reproduced it working when adding @EnableHypermedia. Thanks for the sample, @mvitz.