Incremental annotation processor which helps to (de)serialize Kotlin polymorphic types with Gson in a simple way.
Consider such Kotlin sealed class:
sealed class Shape {
abstract val area: Double
data class Rectangle(override val area: Double) : Shape()
data class Circle(override val area: Double) : Shape()
}
By default Gson doesn't know how to deserialize Shape and such attempt would produce an error:
val shape = Shape.Circle(area = 3.8)
val shapeJson = gsonInstance.toJson(shape)
val deserializedShape = gsonInstance.fromJson(shapeJson, Shape::class.java) // error
println("Shape area is: ${deserializedShape.area}")
- Add few annotations to the sealed class hierarchy:
@Polymorphic
sealed class Shape {
abstract val area: Double
@Subtype
data class Rectangle(override val area: Double) : Shape()
@Subtype
data class Circle(override val area: Double) : Shape()
}
- Try to build your project and link generated code with your gson instance builder:
GsonBuilder().apply {
GeneratedRuntimeTypeAdapterFactories.registerIn(this)
}.create()
Wolla! Step 2 is required only once. For further problems just annotate your types like in step 1.
Library supports not only sealed classes but also other language-common polymorphic types hierarchies.
Annotation processor basically generates RuntimeTypeAdapterFactory objects (gson solution for polymorphic types serialization) and adds each of them into supplied GsonBuilder.
repositories {
maven { setUrl("https://jitpack.io") }
}
dependencies {
implementation("com.gediminaszukas.polyassistant:annotations:<version>")
kapt("com.gediminaszukas.polyassistant:processor:<version>")
}
Copyright (C) 2020 Gediminas Žukas
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
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