Allow `LocalDate` to be serialized/deserialized as number (epoch day)

[kewne]

The LocalDateSerializer only supports serializing LocalDate instances as strings or arrays, both of which suffer from localization issues ("is it year-month-day or year-day-month?").

An alternative would be to use LocalDate#toEpochDay() and LocalDate#ofEpochDay(long), thus allowing a (less human readable but) unambiguous format.

[cowtowncoder]

If there is indeed variant to convert to/from long, supporting @JsonFormat(shape=Shape.NUMBER) would make sense I think? Support should also require deserializer handling.

[kewne]

Yep, both serialization and deserialization should be supported, and using shape=Shape.Number too.

I've forked the repo to try to work on this myself but the build fails with missing poms, is there a specific layout that's needed for building?

[kevinjom]

@kewne in my experience, clone the jackson-bom repo, run mvn clean install and then go back to this repo, run whatever you want.

[kewne]

@kevinjom Got it working, thanks!

@cowtowncoder I'm looking through the code but I'm having difficulty understanding the rationale behind some of the formatting: some zeroes are added to the fractional part of the result "to avoid interpretation as integral number".
I've also found FasterXML/jackson-datatype-jsr310#67 which references something similar, what's the desired format?

[cowtowncoder]

@kewne excellent! I did not write this module originally, so some of the logic predates my changes. I don't recall part about additional zeroes, which should not be necessary to just differentiate between JSON integers vs floating-point numbers.

[cowtowncoder]

As per notes on PR, will merge as soon as we get CLA; will make it in 2.9(.0.pr3)