I wonder: is anyone using Arrow in a project with ...

# arrow

[Marcus Ilgner]

I wonder: is anyone using Arrow in a project with JPA? I'd prefer to model null values in the DB using Arrow's Option<T> instead of T?. But I guess that Hibernate probably wouldn't know how to deal with Option?

[raulraja]

Hi @Marcus Ilgner, I'm not aware of anyone using arrow and hibernate combined, normally it's exposed or other Kotlin ORM like libraries combined with Arrow. I suppose to use Option in Hibernate you would have to implement a AttributeConverter or similar interface to tell Hibernate how to serialize and deserialize the value:
Something like this, untested and assuming Hibernate would support polymorphic converters with generic type args:

import javax.persistence.AttributeConverter
import javax.persistence.Converter

@Converter
class OptionConverter<A> : AttributeConverter<Option<A>, A> {
  fun convertToDatabaseColumn(optionValue: Option<A>): A? =
    optionValue.getOrElse { null }

  fun convertToEntityAttribute(dbValue: A?): Option<A> =
    Option.fromNullable(dbValue)
}

[Marcus Ilgner]

I'll give it a try! Thank you! I'm sure I'll get it to work somehow, but wanted to check whether someone already had a solution. In case the attribute converter method doesn't work, I'll publish whatever alternative I come up with.

[Oliver Eisenbarth]

Probably too far from the initial question, but Spring Data JPA does support the following wrapper types

• java.util.Optional
• com.google.common.base.Optional
• scala.Option
• io.vavr.control.Option
My gut tells me, that things could work with Kotlin-Vavr, too.

Integration code doesn't seem much, you could do a PR for Arrow's Option<T>. 🤪