Inconsistent Pageable Sort serialization between openfeign and spring mvc

[philippeu]

• spring boot version: 2.6.3
• spring cloud version: 2021.0.0 (spring cloud openfeign 3.1.0)

spring serializes Sort as an object

"sort": { "empty": true, "sorted": false, "unsorted": true }

when SortJacksonModule is enabled (feign.autoconfiguration.jackson.enabled: true) Sort is serialize as an array by SortJsonComponent.SortSerializer.

"sort": []

since SortJacksonModule is in the spring context the controller response includes the Sort array creating inconsistency between the controller response with and without SortJacksonModule

[OlgaMaciaszek]

Hello @philippeu, thanks for reporting this. I was able to reproduce the issue. Will work on it.

[OlgaMaciaszek]

@philippeu Have looked into this further. Actually, the data that comes from the sort json of this kind: { "empty": true, "sorted": false, "unsorted": true } is not enough to construct a viable Sort object. If you do not set feign.autoconfiguration.jackson.enabled: true, you will simply get an exception, cause it cannot be deserialised. That's probably why @cbezmen has opted for returning null in such a scenario. Could you provide some more details regarding your usecase?

[philippeu]

Hi Olga,

I have a service returning Pageable.
by default MappingJackson2HttpMessageConverter, serialize Sort object to (using PageImpl)

"sort": { "empty": true, "sorted": false, "unsorted": true }

This service is calling another one via a feign client which is also returning a Pageable

feign.autoconfiguration.jackson.enabled must be set to true in order for the feign client to deserialize the pagination.

once feign jackson is enabled, it registered the SortJacksonModule deserializer and it can read the paginated response.
this is good

the SortJacksonModule serializer is also registered in ObjectMapper of MappingJackson2HttpMessageConverter and then used to serialize the Sort object to

"sort": []

so services having feign jackson enabled do not provide the same response format (sort is serialized as an array) than the ones having feign jackson disabled (sort is serialized as an object).

I work around that by providing a CustomSortJacksonModule serializer and CustomSortJsonComponent.

[OlgaMaciaszek]

@philippeu Could you please provide the code of CustomSortJacksonModule serializer and CustomSortJsonComponent? It will be easier for us to understand your use-case then.