Make it easier to control how the keys in the basic error controller's response are formatted

[x80486]

I have a Spring Boot 2.3.2.RELEASE WebFlux application. In the application.yml I have these settings:

spring:
  jackson:
    property-naming-strategy: SNAKE_CASE
    serialization:
      write-date-timestamps-as-nanoseconds: false
      write-dates-as-timestamps: true

Indeed, almost any JSON response is sent back to the user-agents correctly: in snake case format, except for the auto-generated ones:

This is a usual GET response from the application:

{
  "port_code": "blah",
  "firm_code": "foo",
  "type": "THE_TYPE",
  "status": "BAR",
}

...this is a custom (intercepted within a @RestControllerAdvice) response for a ConstraintViolationException:

{
    "timestamp": 1597344667156,
    "path": "/path/to/resources/null",
    "status": 400,
    "error": "Bad Request",
    "message": [
        {
            "field": "id",
            "code": "field.id.Range",
            "message": "Identifier must be a number within the expected range"
        }
    ],
    "request_id": "10c4978f-3"
}

...and finally this is how Spring Boot auto-generates an HTTP 404 from a controller (based on a ResponseStatusException, that's what I meant by auto-generated ones 😇):

{
  "timestamp": 1597344662823,
  "path": "/path/to/resources/312297273",
  "status": 404,
  "error": "Not Found",
  "message": null,
  "requestId": "10c4978f-2"     <== NOTICE HERE requestId INSTEAD OF request_id ...what the hell?!
}

This is how I'm triggering that in the controller:

return service.findById(id).switchIfEmpty(Mono.error(new ResponseStatusException(HttpStatus.NOT_FOUND)));

If Jackson is configured in such way, wouldn't that apply across the entire application? Looks like there are parts of it not honouring those settings.

Probably, I missed a configuration setting somewhere, but I can't find anything else, so I decided to file a bug report here — and this is the corresponding StackOverflow question.

[wilkinsona]

To avoid people duplicating effort, I'm going to close this in favour of the question on Stack Overflow. We can re-open it if it turns out that a change in Spring Boot is necessary.

[wilkinsona]

It looks like there is some room for improvement here. The response from BasicErrorController is unaffected by Jackson's property naming strategy as it's a Map<String, Object> and the property naming strategy only applies to JavaBean-style properties when a POJO is being serialised. The format of a map's keys can be controlled with a custom StringKeySerializer but it would be nice to make it easier. Returning a POJO from the BasicErrorController may work, but it would be a breaking change and we'd need to be careful that it worked not just with Jackson but with GSON and any other JSON serialisation library that we support.