Is there a way to have a subclass serialized with ...

# serialization

[adk]

Is there a way to have a subclass serialized with the custom serializer of its superclass, without having to declare @Serializable(with= ... ) on every subclass?

[adk]

I'd like to write some generic serialization support for tiny types, such that they get serialized as their contained primitive value and not objects in their own right. e.g.

@Serializable(with=TinySerializer::class)
abstract class Tiny<out T> { abstract val value: T }

data class SortCode(override val value: String) : Tiny<String>()

val sortCode = SortCode("12-34-56")
assertEquals(Json.encodeToString(sortCode), "12-34-56")

[Javier]

Contextual + SerializerModule

[adk]

So, it seems that there are two possible approaches to this, both of which are mildly clunky:
1. @Serializable(with=...) requires a class literal, which forces a custom serializer for every tiny type, because deserialization requires it to construct an instance of the concrete tiny type.
2. Contextual + SerializerModule, as suggested by @Javier, which requires every field the has a tiny type to be annotated with @Contextual, plus listing the serializer in a SerializerModule and passing the module to the Json formatter. This approach does give the option of having just one generic custom serializer because we can call a method and pass parameters to customize the way it works.
Overall, I suspect option one is the least distasteful, as it keeps the boilerplate confined to the declaration of the tiny type. e.g.

@Serializable(with=SortCodeSerializer::class)
data class SortCode(override val value: String) : Tiny<String>()
object SortCodeSerializer: TinySerializer<String, SortCode>(::SortCode, serializer())

[adk]

Am I missing a smarter way of doing this?

[Javier]

if you are the class owner, you can define the serializer with the companion object so you havent to specific it

[Javier]

message has been deleted

[Javier]

Maybe this is the better approach for you to avoid boilerplate

[adk]

for larger types, perhaps so - the serializer is likely to be more unique

[Javier]

Yeah, really I don’t know if this approach let you can block external serializers too, I didn’t try it 🤔

[adk]

what I'm really aiming for is find a way of using tiny types (perhaps not quite going as far as inline classes) in objects that I want to serialize to json as part of an api that I have to call. The idea is to make lots of them, so the serialization has to be extremely low-effort.

[adk]

I'm in complete control of the code, but I don't want to make life too difficult for myself.

[adk]

I suspect three lines of code for each type is borderline acceptable - remembering that that is three lines more than I would need without tiny types and I have to do that for nearly every property. I think I'll give it go for a bit and see how it works.

[Javier]

if you go for that, create templates to automatically create the companion object with it, so you got the serializer in a few seconds

[adk]

ha - would you believe I am writing the intellij live template right at this moment! 😁