[#19921] Add RFC 3339 compatible Jackson module for java.time types

[beikov]

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@bbdouglas (2017/07) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09) @jeff9finger (2018/01) @karismann (2019/03) @Zomzog (2019/04) @lwlee2608 (2019/10) @martin-mfg (2023/08)

[cbornet]

I'm pretty sure Java implementations can already deserialize RFC3339 datetimes...

[cbornet]

The JavaTimeModule can already deserialize RFC3339 datetimes

[beikov]

I'm pretty sure Java implementations can already deserialize RFC3339 datetimes...

I can tell you, it does not. The JavaTime module uses com.fasterxml.jackson.datatype.jsr310.deser.InstantDeserializer for Instant, ZonedDateTime and OffsetDateTime types. This in turn, uses the DateTimeFormatter.ISO_INSTANT, DateTimeFormatter.ISO_OFFSET_DATE_TIME and DateTimeFormatter.ISO_ZONED_DATE_TIME formats respectively for parsing.
You can look into the javadocs of DateTimeFormatter and easily figure out that it implements ISO8601 which has T as the only valid separator between date and time, whereas RFC3339 also allows a space character.

If you don't believe me, try it out for yourself: https://onecompiler.com/jshell/42vrgfpy8

[cbornet]

As per its ABNF, RFC3339 doesn't support space as a separator.
But it's true that there's a note that says applications may choose to use space... I wouldn't recommend to use it though...
So maybe we could be lenient on deser and accept it 🤔
Do people really use RFC3339 with space separator ?

[beikov]

I integrated an application which uses this format, so clearly, there is precedent for this need. I doubt that application will change the representation.
I can't speak for other users, but if OpenAPI claims that RFC3339 format is supported, then the OpenAPI generator should respect that.

[martin-mfg]

Hi @beikov, thanks for the PR! Apart from the small topics I commented on separately, this PR looks good to me. I tested the changes locally and can confirm that the changes enable the parsing of additional timestamp formats.

[martin-mfg]

I guess this new line shouldn't be inside the {{#openApiNullable}} block, right?

[martin-mfg]

This super constructor is deprecated (see here). Could you please switch to a different one? I guess you could simply use the one recommended in the above link. And for the additional parameters required there, you could use the default values. (DEFAULT_NORMALIZE_ZONE_ID=true, DEFAULT_ALWAYS_ALLOW_STRINGIFIED_DATE_TIMESTAMPS=false)

[martin-mfg]

optional, not required for PR approval imo: Currently these supporting files are added even if the chosen library doesn't use them at all. You could introduce an additional if here to only add the files where they are actually supported.