it seems most json APIs expect the type to be known in order to read the value

Does anyone have an example of using an

expect typealias

as a member of a

data class

that can be serialized?

Hi! I have started a new multiplatform project in IDEA (kotlin version 1.3.61), added the classpath, added

id("kotlinx-serialization") version "1.3.61"

to the plugins block and

implementation(serialization("-common"))

dependency to commonMain. Then I try to annotate a data class with

@Serializable

and IDEA says it fine, but when running gradle build it says

Cannot access 'Serializable': it is internal in '<http://kotlin.io|kotlin.io>'

. It seems similar to this issue: https://github.com/Kotlin/kotlinx.serialization/issues/395 but here the solution was to add the plugin to the plugin block - which I have already done. Any suggestion what might cause this?

I'm working in a multiplatform project where we have a few

actual typealias MyClass = String

for some platforms, while using

actual data class MyClass(val someVal: String)

on other platforms. We also have an

expect val MyClassSerializer: KSerializer<MyClassSerializer>

which we set equal to either

StringSerializer

or the generated serializer for the data class. We declare

contextual(MyClass::class, MyClassSerializer)

in our common serialization context. On platforms where we typealias to Strings, we get a

SerializerAlreadyRegisteredException: Serializer for class String already registered in this module

, even though our

MyClassSerializer

points to the built-in

StringSerializer

. Is there a way to avoid this error? • I see the

overwriteWith

option, but it feels scary to use this since I'd be overwriting behavior for ALL Strings. It seems easy to declare a custom serializer for a type without realizing that this might change behavior for every String in your app. • My understanding is that using an inline class instead of typealias might help here, but I'm not sure about the state of inline classes in multiplatform. • Can I contextually register a serializer if-and-only-if there isn't already one registered for the type? • Is it possible for the contextual registration to do an equality check on the

KSerializer

and not throw an error if we're just redeclaring the preexisting association?

I have a data class in a module that is not dependent on kotlinx.serialization. Is there an easy way to make that class serializable in another module, without having to manually write the serializer?

Anyone know how I can resolve this StackOverflowError with the Kotlin compiler with Kotlinx.Serialization? I have an old multi-module project that I just upgraded to kotlin 1.3.61 from 1.3.30 and get this error when I try to build. I read it might have something to do with declaring a type alias in a different module from where it was originally declared, but not sure if that is relevant as it says this issue was fixed in 1.3.60.

I am attempting parse a complex JSON structure with a custom double serializer. Is there a simpler way to tell the parser to use a customer serializer instead of having to mark every property with

@Serializable(with = CustomDoubleSerializer::class)

since there are a large number of these formatted doubles. Thank you.

I am trying to serialize a sealed class contains Option and i am using following Custom Serializer https://github.com/sksamuel/avro4k/blob/master/avro4k-arrow/src/main/kotlin/com/sksamuel/avro4k/arrow/OptionSerializer.kt While i serialize Option<Pair> getting following error

class kotlin.Pair is not registered for polymorphic serialization in the scope of class kotlin.Any

Find my sample code here

@Serializable
    sealed class Fruit(@Serializable(OptionSerializer::class) var meta: Option<@Polymorphic Any>) {
        @Serializable
        data class Blueberry(@Serializable(OptionSerializer::class) val metaData: Option<Pair<String, String>> = Option.empty()) :
            Fruit(metaData)
    }

    @Serializable
    data class Basket(
        val blueberry: Fruit.Blueberry = Fruit.Blueberry()
    )

    @Test
    fun `Test Serialize Fruit`() {
        val basket = Basket(
            Fruit.Blueberry(Option.just(Pair("firstVal", "SecondVal")))
        )
        validateSerialize(basket, Basket.serializer())
    }

how would i do something like this? https://stackoverflow.com/questions/59331257/jackson-deserialization-with-no-type

@Serializable
data class RowBinMeta(val name: String, val coord: Array<Int>, val typ: /*an enum*/ TypeMemento)

val meta: List<RowBinMeta> =  RowBinMeta.RowBinMetaList(elements)
val out = Json(JsonConfiguration.Default).toJson( meta  )

Exception in thread "main" kotlinx.serialization.SerializationException: Can't locate argument-less serializer for class kotlin.collections.List. For generic classes, such as lists, please provide serializer explicitly. what am i missing?

I have a simple

@Serializable

class with lots of members like this:

@Serializable
    class TooManyMembers {
        val mem1: Int? = null
        val mem2: Int? = null
        .
        .
        .
        val mem248: Int? = null
    }

That's a class with 248 members. Instantiating this member with

val obj = TooManyMembers()

throws this error at runtime:

Too many arguments in method signature in class file SerializationTests$TooManyMembers
java.lang.ClassFormatError: Too many arguments in method signature in class file SerializationTests$TooManyMembers

If I remove just one member, no more of that error. Is that really a limit (247) with numbers of members one can have in a

@Serializable

class? What can I do if I have an object with more members? 247 seems way too low. This is with

0.14

and kotlin

1.3.61

Is there a way to deserialise JSON to a

Map

? I've tried just passing HashMap has a type but I'm just seeing

Can't locate argument-less serializer for class java.util.HashMap. For generic classes, such as lists, please provide serializer explicitly.

Did anyone struggle with

kotlinx-serialization

? I’m using

0.14.0

, and I’m gettin pretty randomly

java.lang.NoClassDefFoundError:

, some time it works, some time it doesn’t 🤷

Hey, I just ran into a weird issue with custom serializers. I have following code:

class InlineSerializerTest {
    @Test
    fun `simple TestClass serialization test`() {
        val json = "\"test\""
        val parsed = Json.parse(TestClass.Companion, json)
        assertEquals(
            TestClass("test"),
            parsed
        )
    }
}


@Serializable(with = TestClass.Companion::class)
data class TestClass(val a: String) {

    @Serializer(forClass = TestClass::class)
    companion object : TestSerializer {
        override val descriptor: SerialDescriptor = StringDescriptor

        // when removing this function the serialization crashes.
        override fun deserialize(decoder: Decoder): TestClass {
            return TestClass(decoder.decodeString())
        }

        override fun serialize(encoder: Encoder, obj: TestClass) = throw UnsupportedOperationException()
    }
}

interface TestSerializer: KSerializer<TestClass> {
    override fun deserialize(decoder: Decoder): TestClass {
        return TestClass(decoder.decodeString())
    }
}

As you can see in the companion object, I redefined the deserialize function with the same body as the extending interface. When removing this implementation the deserialization crashes:

Invalid JSON at 0: Expected '{, kind: CLASS'
kotlinx.serialization.json.JsonDecodingException: Invalid JSON at 0: Expected '{, kind: CLASS'
	at kotlinx.serialization.json.internal.JsonReader.fail(JsonReader.kt:293)
	at kotlinx.serialization.json.internal.StreamingJsonInput.beginStructure(StreamingJsonInput.kt:39)
	... // if needed I can provide the full stack later

Any idea how to resolve this? Whats really weird is that the error says that a

class

kind descriptor would be used, but String is definetly not a class kind type.

it looks like a lot of serialization internals are leaking into my project's API. is there a way to suppress that?

I'm trying to build a complicated JSON object. But the

JsonObjectBuilder

doesn't have any

suspend

functions. What would then be the recomended way of building a JSON object across multiple coroutines?

Does serialization not support generics? I am working on a multiplatform project (Targetting Android and JS) -

@Serializable
class BaseResponse<T> {

    val data: T? = null

    @SerialName("status")
    val isSuccess: Boolean = false

    @SerialName("session")
    val isSessionExpire: Boolean = false

    @SerialName("message")
    val message: String = ""
}

Can this be serialized -

BaseResponse<String>

? There is an error logged ->

java.lang.UnsupportedOperationException: The only generic classes supported for now are standard collections
got class class dto.BaseResponse (Kotlin reflection is not available)

I did read the documentation regarding requiring a custom serializer in case of generics but wasn't able to understand it. Any help would be much appreciated.

has anyone seen this error before: java.lang.NoClassDefFoundError: Failed resolution of: Lkotlinx/serialization/internal/GeneratedSerializer? it's happening when running connected tests on Android.

Is there any workaround for serializing inline classes (or UInt/UShort/UByte specifically). I know inline classes are not supported for serialization right now, but is there a way to make it work (no matter how verbose)?

there is no mpp stream abstraction (yet)

Hi! Did anyone faced this exception before?

UnknownFieldException: Unknown field for index -2

I'm getting this when I try to use Mapper.unmap(serializer, map) call. I made a minimal reproduction code snipet.

Hey all! I've got an event stream from JS (legacy library) into Kotlin. I've got data classes under sealed classes that I want to map from type names to serializers so that I can easily parse from an event to the correct object. Here are the classes:

sealed class ManyHandsData: JSAction() {
        @Serializable
        data class handError(val message: String, val errorCode: Int): ManyHandsData()

        @Serializable
        data class DATA_INPUT(val openSensorInput: Int, val closeSensorInput: Int): ManyHandsData()

        @Serializable
        data class currentGripDidChangeExtended(val currentGrip: Int, val buttonSelected: Int, val currentButtonIndex: Int): ManyHandsData()
    }

I've tried this:

internal val handDataActionSerializers = listOf(
    JSAction.ManyHandsData.handError.serializer(),
    JSAction.ManyHandsData.DATA_INPUT.serializer(),
    JSAction.ManyHandsData.currentGripDidChangeExtended.serializer()
).associateBy { it.descriptor.name}

which doesn't have the simple name. I was thinking maybe Delegates are the way to go (doing this for mapping js methods) but I'm struggling to think how to integrate that with data classes.. The goal would a mapping similar to above which allows me to retrieve a serializer by the string of an identifier (eg "DATA_INPUT")

Does anyone know if you can make AppCode see generated serializers? Or if there is an opened issue for that problem?

Also, @Transient does not seem to be working correctly on MPP expect/actual. I'm expecting a base class and adding extra transient field on one platform, however it still gets serialized

Hi! I am struggeling with some serialization and was hoping somebody could help.. I want to pass in a list of objects as a body to a (ktor) request. This is where I’m doing the serialization.

val userIds: List<MemberInput> = listOf(...)
val json: JsonElement = Json.nonstrict.toJson(MemberInput.serializer().list, userIds)
<http://client.post|client.post><HttpResponse> {
                header("Content-Type", "application/json")
                header("Accept", "*/*")
                body = json
}

This gives me an exception when setting it as the body to the request:

java.lang.ClassCastException: kotlinx.serialization.json.JsonObject cannot be cast to java.lang.String

. (I should be able to set the

userIds

as body out of the box, but for debugging purposes…) First; is this a kotlinx.serialization or a ktor issue? Secondly; what’s wrong? 🙂 I appreciate any help! 🙂

Is there any non-internal analog for

SerialClassDescImpl("MyClass")

in

0.14.0-1.3.70-eap-134

?

Is there any way to define a serializer for a top-level list as a contextual serializer in a

SerializersModule

?

Has anyone hooked up kotlinx serialization with Spring Boot?

Is it possible to handle polymorphic JSON structures (are JSON structures that change depending on what is sent as input) with KotlinX Serialization?

What is the reasoning behind using

fun serializer() =

instead of

val serializer get() =

/

val serializer =

? I’m working on a library which stands before a similar decision and would love to hear it :)