I have a sealed class `Event<P>`, and a bunch of objects that inherit from the class with a fe...

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[Andrew]

I have a sealed class Event<P>, and a bunch of objects that inherit from the class with a few different types for P. I receive some json that has a name field so that I can match it to one of the objects, and data field that I want to deserialize into an object of type P. Is there any way to do this without doing a case-by-case when for each event type?

[Jakub Pi]

What are you using for JSON serialization? I know that Jackson has capabilities for doing this.

[Andrew]

I am using gson but I don't really mind switching to jackson

[Dominaezzz]

Here's some extra motivation lol. https://kotlinlang.slack.com/archives/C0922A726/p1587240508410600?thread_ts=1587239522.408900&cid=C0922A726

[Dominaezzz]

kotlinx.serialization also supports polymorphism. (Although combining it with generics is a bit.... complicated)

[Jakub Pi]

Take a look at the docs for @JsonTypeInfo inside Jackson. There are a few ways to wire it in, but I've never used it with Generics.

[Jakub Pi]

Basically you'll want to annotate your Event class and then register the subtypes on your ObjectMapper (which is the main class for Jackson)

[Adam Powell]

Moshi is also a good choice if you're already using gson, it has a kotlin code generator to avoid reflection as well

[nkiesel]

@jw: We are internally converging on Jackson (and thus away from Gson among others), but is this "never use Gson" really an official (and quotable) statement from the Gson project? If yes, I might have arguments for accelerating that convergence.

[jw]

You'll get that statement from 2/3 maintainers. Is simple majority good enough?

[nkiesel]

Sure. An Moshi or Jackson are recommended replacements?

[jw]

Or kotlinx.serialization

[nkiesel]

Yeah. However, we also use YAML a lot and no multi-platform yet and still have legacy Java code and thus Jackson currently is the front-runner