Hey friends! Looking for some help on keeping a subset of JSON in string-form I have JSON like

{
  "id": "file",
  "value": "File",
  "popup": {
    "menuitem": [
      {
        "value": "New",
        "onclick": "CreateDoc()"
      },
      {
        "value": "Open",
        "onclick": "OpenDoc()"
      },
      {
        "value": "Save",
        "onclick": "SaveDoc()"
      }
    ]
  }
}

I'd like to represent it with a

data class Menu(val id: String, val value: String, val popup: String)

where the

popup

subtree is stored as a String of valid JSON, instead of having to deserialize the whole nested

popup

structure. Happy to write a custom serializer for this because it doesn't happen too frequently in our codebase.

Hi, how can I configure kotlinx JSON serializer to not quote the key? Like this:

{noQuote: "foobar"}

Just a while ago it was working like a charm. Not sure why it's not working right now. Any idea?

Hello everyone, I have a class hierarchy like the following, and I have an API that return a list of

User

I can retrieved Users using two different end-points, The first one return

recent

users and the second one return

popular

users, for both popular and recent end-points the data returning by the API has the same structure except one thing The recent end-point return a json like this, that differ from the popular end-point at the recent field

{
  "data": {
    "recent": { ... } // Here the difference
   }
}

And the popular end-point return a json like this, that differ from the recent end-point at the popular field

{
  "data": {
    "popular": { ... } // Here the different 
   }
}

Here the class hierarchy

@Serializable
data class ApiResponse(
  @SerialName("data")
  val apiData: Data
)

@Serializable
data class Data(
  @SerialName("recent") // My problem is here
  val page: Page
)

@Serializable
data class Page(
  val currentPage: Int,
  val from: Int,
  val perPage: Int,
  val results: List<User>,
)

For the

Data

class, there is a way to customize the behavior of the

SerialName

annotation to deal both with recent and popular name as the

Page

class has the same structure for recent and popular end-point without having to duplicate stuff ??

Hi all, I get this error

Can't use arguments with defaults for serializable annotations yet

every time I use

@JsonNames

annotation Kotlin=1.5.21 Ktor=1.6.3 I'm not using the latest version of Kotlin because my project uses Jetpack Compose

The root cause java.lang.IllegalArgumentException was thrown at: org.jetbrains.kotlinx.serialization.compiler.backend.jvm.SerializerCodegenImpl.addSyntheticAnnotationsToDescriptor(SerializerCodegenImpl.kt:123)

📣 kotlinx.serialization

1.3.0-RC

has been released! It contains a lot of interesting features and improvements, such as: • Integration with Java streams; • Property-level control over defaults values encoding; • Per-hierarchy polymorphic class discriminators; • Excluding null values from JSON serialization. You're welcome to evaluate it and share your feedback. Full release notes here: https://github.com/Kotlin/kotlinx.serialization/releases/tag/v1.3.0-RC

Hi, I'm using serialization 1.5.30 and I'm having a weird issue when I try to parse a JSON :

Exception in thread "main" kotlinx.serialization.json.internal.JsonDecodingException: Unexpected JSON token at offset 0: Expected end of the object '}', but had '{' instead
JSON input: {"keywords":[],"softKeywords":[],"modifierKeywords":[],"specialIdentifiers":[],"operators":[]}
	at kotlinx.serialization.json.internal.JsonExceptionsKt.JsonDecodingException(JsonExceptions.kt:24)
	at kotlinx.serialization.json.internal.JsonExceptionsKt.JsonDecodingException(JsonExceptions.kt:32)
	at kotlinx.serialization.json.internal.JsonLexer.fail(JsonLexer.kt:493)
	at kotlinx.serialization.json.internal.JsonLexer.fail(JsonLexer.kt:215)

Hi.. I wanted to know how to serialize a json generic property whose type is known only at runtime. Eg:

"response":{
"value":5
}"

Value can be Int or string or a list of some other type.

Is java's

serialVersionUID

completely unnecessary when saving to disk using serialization and then deserializing to a potentially modified class type later?

I have some nested generic sealed hierarchies using

@Serializable

and getting the following (in thread) exception from compiler when building.. Is this a known issue? Is there something one must avoid to prevent this? Edit: Upgrading 1.2.1 -> 1.2.2 fixed it!

Trying to serialize generic data class having with default value produces empty JSON object

{}

Easiest way to reproduce this issue is to try official generic classes example, add

data

modifier to the class and have default value (eg. in thread) https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/basic-serialization.md#generic-classes I'm using kotlinx.serialization v1.2.2 and Kotlin v1.5.21 Update: All I had to do was read this section of doc 😅https://github.com/Kotlin/kotlinx.serialization/blob/master/docs/json.md#encoding-defaults

Very frustrating.. Small tweak in data classes and all of a sudden kotlinx.serialization causes compiler errors like this. Is there any known pitfalls to avoid getting problems like this?

org.jetbrains.kotlin.codegen.CompilationException: Back-end (JVM) Internal error: Couldn't transform method node:
write$Self (Ldev/kantis/Square;Lkotlinx/serialization/encoding/CompositeEncoder;Lkotlinx/serialization/descriptors/SerialDescriptor;Lkotlinx/serialization/KSerializer;Lkotlinx/serialization/KSerializer;)V:
  @Lkotlin/jvm/JvmStatic;()
    // annotable parameter count: 5 (visible)
    // annotable parameter count: 5 (invisible)
    @Lorg/jetbrains/annotations/NotNull;() // invisible, parameter 0
    @Lorg/jetbrains/annotations/NotNull;() // invisible, parameter 1
    @Lorg/jetbrains/annotations/NotNull;() // invisible, parameter 2
    @Lorg/jetbrains/annotations/NotNull;() // invisible, parameter 3
    @Lorg/jetbrains/annotations/NotNull;() // invisible, parameter 4

[Full error in thread]

What did I do wrong? Why

stars

is not encoded to json❓

Does kotlinx-serialization allow serialization/deserialization to html? or is there any useful library to do this?

Hi everybody. May be someone is familiar with changes around Kotlin's 'object' (and may be sealed classes) made between 1.3.50 and 1.4.30 ? I missed that and cannot find in changelog anything related. Following code works quite different on these versions:

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type")
sealed class A {
    @JsonTypeName("B")
    object B: A()
    @JsonTypeName("C")
    object C: A()
    @JsonTypeName("D")
    data class D(val i: Int): A()
}

class JsonTest {
    private val objectMapper = jacksonObjectMapper().apply(configureObjectMapper)
    private fun <T> parse(str: String, clazz: Class<T>): T = objectMapper.readValue(str, clazz)
    private fun <T> stringify(value: T): String = objectMapper.writeValueAsString(value)

    @Test
    fun testPatternMatching() {
        val x1 = A.B
        val x2 = parse(stringify(x1), A::class.java)
        val x3 = A.C

        listOf(x1,x2,x3).forEach {
            when(it) {
                A.B -> println("b ${it as Any}")
                A.C -> println("c ${it as Any}")
                is A.D -> println("d ${it as Any}")
                else -> println("? ${it as Any}")
            }
        }
        assertEquals(A.B, x1)
        assertEquals(A.B, x2) // <--- failed assertion in 1.4.30
        assertEquals(x1, x2)
    }
}

In 1.3.50 projects, it prints:

b com.example.A$B@184a254d
b com.example.A$B@184a254d
c com.example.A$C@41443428

In 1.4.30 (and 1.5.x) projects, it prints:

b com.example.A$B@12a1cc8d
  ? com.example.A$B@7b2edf94
  c com.example.A$C@73baae4e

and test fails with

expected:<com.example.A$B@12a1cc8d> but was:<com.example.A$B@7b2edf94>

As I can see - after serialization/deserialation I got 2nd A.B object (nonsense for a singleton). This code can be fixed by writting 'is A.B', in that case both instances (x1 and x2) will be matched. But who knows what is going on here and why it changed since 1.4.x ?

umm so I have this thing

@Serializable
data class ProjectIdWrapper(
	val id: ProjectId,
	val item: Project)

@Serializable
data class Project(
	val projectProperty1: String,
	val projectProperty2: String
)

but I want to have ProjectIdWrapper serialized/deserialized as

{
  "id": 12121,
  "projectProperty1": "AAA",
  "projectProperty2": "BBB"
}

Is this possible? Or even better, can the IdWrapper be made generic? 😊

Hello. I am trying to deserialize a json array of "unstructured" operation descriptions into an object. The format is similar to

["create", true, {more: "properties"]

. There are more types than just the

"create"

shown here. I have attempted many different approaches but none were successful so far. What would be the best approach for such an input?

I'm not sure what this error is trying to tell me. (Its trying to serialize "type")

Exception in thread "DefaultDispatcher-worker-10" kotlinx.serialization.json.internal.JsonDecodingException: Unexpected JSON token at offset 14: Expected beginning of the string, but got ,

JSON input: {"type":"rich","author":{"name":"author"}}

Ok, i made some progress by using

override val descriptor: SerialDescriptor = buildSerialDescriptor("Create", StructureKind.LIST) {
      element("target", serialDescriptor<String>())
      element("method", serialDescriptor<String>())
      element("properties", serialDescriptor<Map<String, Any>>())
    }

The remaining problem now is the Map<String, Any> part where i want to resolve the properties into a Map with properties and possible sublists. However there is not serializer for

Any

. Any advice on how to serialize the Any correctly within the properties map?

Hi all please tell me how can I represent this object as a given json? {'response': {'code':0, 'message':'msg'}}

@Serializable
data class ReportUserResponse(
    val message: String,
    val code: Int,
)

without having to create another class with a 'response' field ?

I would like to serialize this class:

@Serializable
data class RpcRequest(
  @SerialName("jsonrpc") val jsonrpc : String,
  @SerialName("id") val id : Int,
  @SerialName("method") val method : String,
  @SerialName("params") val params : List<@Contextual Any>?,
)

where

params

could be a list of any kind of object I currently get this error:

Serializer for class 'Any' is not found.

Mark the class as @Serializable or provide the serializer explicitly.

An example of RpcRequest object:

val req = RpcRequest("2.0",2342,"getData",listOf("erwrwee",{"encoding":"base64"}))

How can it be properly serialized?

may i add a general comment? kotlinx serialization is hard. anything but a direct conversion requires tremendous work. if it weren't for KMP i would stick with gson or moshi. Hope other json serialization libraries become KMP capable soon.

Where can I find the source code for this library's gradle and kotlin plugins?

Is current serialization compatible with 1.6-M1? I am willing to try EAP, but from experience I know that the serialization is frequently broken on EAPS.

📣 kotlinx.serialization

1.3.0

has been released! This release brings a lot of new features, such as preview of

<http://java.io|java.io>.*Stream

-based serialization, additional control over default and nullable properties, and more. Check out the blogpost and the changelog: https://blog.jetbrains.com/kotlin/2021/09/kotlinx-serialization-1-3-released/ https://github.com/Kotlin/kotlinx.serialization/blob/v1.3.0/CHANGELOG.md

Hi! I am trying to use

JsonContentPolymorphicSerializer

to manually select what de-serializer to use for my polymorphic class hierarchies, while using

JsonTransformingSerializer

to remove the

type

fields at serialization. I am doing this:

inline fun <reified T : Any> noDiscriminatorPolymorphic(crossinline serializerSelector: (element: JsonElement) -> DeserializationStrategy<out T>): KSerializer<T> {
    val serializer = object : JsonContentPolymorphicSerializer<T>(T::class) {
        override fun selectDeserializer(element: JsonElement): DeserializationStrategy<out T> {
            return serializerSelector(element)
        }
    }
    return NoDiscriminantSerializer(serializer)
}

class NoDiscriminantSerializer<T : Any>(serializer: KSerializer<T>) :
    JsonTransformingSerializer<T>(serializer) {
    override fun transformSerialize(element: JsonElement): JsonElement {
        val content =
            element.jsonObject.mapValues { (_, v) -> if (v is JsonObject) JsonObject(v.jsonObject - "type") else v } - "type"
        return super.transformSerialize(JsonObject(content))
    }
}

and then this:

val myFormat = Json {
    serializersModule = SerializersModule {
        contextual(noDiscriminatorPolymorphic { element ->
            when {
                "thisField" in element.jsonObject -> ThisClass.serializer()
                "thatField" in element.jsonObject -> ThatClass.serializer()
                else -> error("Unknown subclass")
            }
        })
    }
}

But the

type

fields are always serialized. Does anyone know what I am missing?

Hi, after updating to 1.3.0 and trying out 'explicitNulls = false' I get this:

Exception in thread "main" java.lang.NoSuchMethodError: 'void kotlinx.serialization.json.JsonBuilder.setExplicitNulls(boolean)'

at com.banktrade.sequoia.serialization.SerializationConfig$updateSerialFormat$1.invoke(SerializationConfig.kt:55)

at com.banktrade.sequoia.serialization.SerializationConfig$updateSerialFormat$1.invoke(SerializationConfig.kt:47)

at kotlinx.serialization.json.JsonKt.Json(Json.kt:137)

at kotlinx.serialization.json.JsonKt.Json$default(Json.kt:135)

Anyone else tried this one out already?

I have the following enum class that has a custom serializer

@Serializable(with = RepresentedAreaSerializer::class)
enum class RepresentedArea(override val value: String) : StringEnum {
  Alaska("AK"),
  Alabama("AL"),
  AmericanSamoa("AS")
  ...
}

object RepresentedAreaSerializer : StringEnumSerializer(RepresentedArea.values())

abstract class StringEnumSerializer<T>(
  enumValues: Array<out T>,
) : KSerializer<T> where T : StringEnum, T : Enum<T> {

  private val enumMap = enumValues.associateBy { it.value }

  override val descriptor get() = PrimitiveSerialDescriptor("StringEnumSerializer", PrimitiveKind.STRING)
  override fun serialize(encoder: Encoder, value: T) = encoder.encodeString(value.value)
  override fun deserialize(decoder: Decoder): T = checkNotNull(enumMap[decoder.decodeString()])
}

When I try to serialize this value with the following method, I get an error that

Serializer for class 'RepresentedArea' is not found.

@Test fun foo() {
    val json = Json { prettyPrint = true}
    assertEquals("VA", json.encodeToString(RepresentedArea.Virginia)) // runtime error
  }

The strange bit is that I can serialize it as a part of other object structures. For example, the following works for both serializing and deserializing.

@Serializable class GetLegislatorsByAddressRequest(
  val streetAddress: String,
  val city: String,
  val state: RepresentedArea,
  val postalCode: String,
)

I'm a bit stuck on this error. Does anyone have any ideas what I'm doing wrong?

I'm trying to convert a

JsonObject

to

Map<String, Any>

, but am stumped on

JsonPrimitive

. It stores all values as

String

, so it doesn't seem possible to get a float/boolean/etc. unless you know its type ahead of time. Is there a (simpler) way to accomplish this?