For such a type, you would need to write a custom serialiser, not just whitelist the type.
However, may I ask why you want to use that type specifically? It’s more conventional to use java.time.Instant to record times on ledger when you need a time to machine precision, or the other types like java.time.LocalDateTime to record a time to human levels of precision (e.g. “8pm Tuesday” when no time zone is specified)
If you have data that’s starting from java.sql.Timestamp it’d be better to convert to an Instant, as that type has a much better design.