Precondition failed for PUT methods on ResponseEntity return types [SPR-15780]

[spring-projects-issues]

Danny Hamrick opened SPR-15780 and commented

We have an app that has recently been converted from Spring Boot 1.3.8 to 1.5.2. We are managing the ETag and LastModified headers. Our code worked fine with 1.3.8 but now causes a 412 Precondition Failed return code. We traced the return code to ServletWebRequest.validateIfUnmodifiedSince(). It is checking the flag after we set the new value. The functional change is from #18168. I'm not sure how we are suppoed to manage these headers now.

We put together an example of what we are doing. Hopefully you can advise us on the proper way to proceed.

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Backported to: 4.3.15

[spring-projects-issues]

Brian Clozel commented

Hi Danny Hamrick

First, I really apologize for not paying attention to that issue for so long; I should have raised its priority but didn't realize it could be considered as a regression, and not just a request for an opinion.

I've just fixed this and it should be available in 4.3.15.BUILD-SNAPSHOT and 5.0.5.BUILD-SNAPSHOT shortly. The preconditions checks when processing the returned ResponseEntity won't be triggered for HTTP methods other than "GET" and "HEAD".

I've also taken a look at the sample you provided. As a workaround and/or an improvement in your codebase - you could definitely leverage the ServletWebRequest::checkNotModified methods and return the response body as an object (check the reference documentation on HTTP caching at the controller level for more on that). This will delegate the task of dealing with the HTTP caching spec to Spring Framework (checking conditional requests and setting response headers accordingly).

I'd be also happy to provide guidance on specific samples.

Thanks for your report!