How do I fail json deserialization if non nullable fields ar kotlinlang #announcements

Gson or Moshi don’t provide such feature out of the box (because they are target Java, where you don’t have nullable types, all non-primitive types are nullable). You need some adapter for that. For example for Kotlin Data classes there are Moshi adapters: Kotshi (code generation of adapters) and moshi-kotlin (based on kotlin-reflect). Not sure about Gson, but I used auto-value-gson to generate AutoValue adapters with such feature, but it doesn’t work with Data classes, only with AutoValue classes

Also, as an alternative (but experimental) solution you can take a look on kotlinx.serialization #serialization It supports Kotlin nullability out of the box

aeruhxi

02/12/2018, 9:13 AM

Is it a standalone thing that supports working with json?

Would it be safe to use this in production?

gildor

02/12/2018, 9:17 AM

standalone thing

What do you mean? Yes kotlinx.serialization supports Json out of the box. But it’s experimental and under active development.

aeruhxi

02/12/2018, 9:24 AM

I meant if it was supposed to work with other json lib like gson or has its own. Anyway. I got the answer. Thanks

gildor

02/12/2018, 9:25 AM

No, it’s completely separate tool that generates bytecode directly on compile time from your annotated data class

Also it’s multiplatform and will be an official multiplatform serialization tool for Kotlin

cedric

02/13/2018, 1:53 AM

@gildor @aeruhxi FYI in Klaxon, I just use default values in Kotlin to take care of that problem

gildor

02/13/2018, 1:54 AM

Gson also will use default value if class has default constructor

@cedric But what will happen If I have non-null value in data class and Json doesn’t contain this value?

cedric

02/13/2018, 2:10 AM

If you didn't specify a default value, Klaxon will throw an exception

gildor

02/13/2018, 2:12 AM

yeah, make sense

aeruhxi

02/13/2018, 3:03 AM

Thanks, I will consider Klaxon

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