JsonDecodingException: Polymorphic serializer was not found for missing class discriminator ('null') #1382
Comments
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Deserialization works if I pass classDiscriminator into input json as: |
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Looks like Serialization/Deserialization works only through below steps:
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If you do not need polymorphism in this place you can deserialize like this |
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@shanshin I agree with that. But open polymorphism is the requirement. Is there any way where we can use the discriminator that is already available in Json. We already have a key "type" in core json structure (from Module class). Can you provide a way to use that core json key as discriminator instead of using built-in discriminator or custom classDiscriminator? I tried something like this: |
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I think that |
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@sandwwraith Yes I achieved it using |
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We can close this issue 👍 |
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@iChintanSoni hey, I follow your code and write this @Serializable(with = ItemSerializer::class)
sealed class Item {
abstract val type: String
@Serializable
data class A(val number: Int): Item() {
override val type: String = "A"
}
@Serializable
data class B(val number1: Int, val number2: Int): Item() {
override val type: String = "B"
}
}
object ItemSerializer: JsonContentPolymorphicSerializer<Item>(Item::class) {
override fun selectDeserializer(element: JsonElement): DeserializationStrategy<Item> {
return when (element.jsonObject["type"]?.jsonPrimitive?.content) {
"A" -> Item.A.serializer()
"B" -> Item.B.serializer()
else -> throw Exception("Unknown Item type")
}
}
}
class SealedClassSerializationTest {
@Test
fun testSerialization() {
val formatter = Json {
encodeDefaults = true
prettyPrint = true
}
val item = Item.A(1)
val s = Json.encodeToString(item)
println(s)
val result = Json.decodeFromString<Item>(s)
println(result)
}
}but I found that it is very strange, right ? |
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@nesteiner Try |
Describe the bug
Unable to deserialize json string. Upon performing decodeFromString() throws Exception:
To Reproduce
I wrote a test case for demonstrate this:
Expected behavior
It should deserialize.
Environment
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