Hello all. I'm using the lib, 

jackson-module-kotlin,

 to serialize but I'm having an error:

Hi folks, apologies in advances for the not “kotlin specific” question. Does anyone knows if it is possible to set the mapper to write nested json as a string? For example, a map like

mapOf("key" to mapOf("innerKey" to "value"))

serialized as

{ "key": "{\"innerKey\": \"value\"}" }

instead of

{"key": {"innerKey": "value"}}

hello 👋 JSON fields can have 3 states ->

undefined

(field is omitted),

null

(field=null) and also can have a

value

(field=value). Within JVM we either have value or no-value (i.e.

null

) so we are trying to represent those 3 states using Kotlin sealed classes - something along the lines

sealed class OptionallyDefined<T> {
    object Undefined : OptionallyDefined<Nothing>()
    data class Defined<T>(val data: T) : OptionallyDefined<T>()
}

Unfortunately cannot get the deserialization to work. I tried using custom serializer (i.e.

@JsonDeserialize(using = NullAwareDeserializer::class)

) but cannot get it to work correctly. Any pointers would be greatly appreciated!

Hi all. I am trying to understand the equivalent for Mapping Nested Values with Jackson for example:

public class SimpleClass {

    private String path;

    @JsonProperty("somePath")
    private void unpackPath(Map<String, Object> somePath) {
        this.path = (String) somePath.get("toString");
    }
}

When I use the IDE convertor I am getting this:

class SimpleClass {
    private var path: String? = null
    @JsonProperty("somePath")
    private fun unpackPath(somePath: Map<String, Any>) {
        path = somePath["toString"] as String?
    }
}

Is that correct ?

Hello, I'm having a problem with deserializing object using delegate interface, any ideas?

Hello 👋 I got a requirement for my server to accept either a single JSON object or an array of those so I modeled it using a sealed class

sealed class MyServerRequest

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
data class SingleRequest(val request: String) : MyServerRequest()

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
class BatchRequest @JsonCreator constructor(@get:JsonValue val requests: List<SingleRequest>) : MyServerRequest()

Between those two there is no extra

type

field that I could use to detect correct type using

@JsonTypeInfo/@JsonSubTypes

. Instead, I parse the incoming requests to a

JsonNode

and check whether it is an array to determine appropriate target, i.e.

val jsonNode = rawRequest.bodyToMono(JsonNode::class.java).awaitFirst()
if (jsonNode.isArray) {
  objectMapper.treeToValue(jsonNode, BatchRequest::class.java)
} else {
  objectMapper.treeToValue(jsonNode, SingleRequest::class.java)
}

the above works fine but I'd like to simplify it and use custom deserializer to handle it, i.e.

@JsonDeserialize(using = MyRequestDeserializer::class)
sealed class MyServerRequest

class MyRequestDeserializer : JsonDeserializer<MyServerRequest>() {
    override fun deserialize(parser: JsonParser, ctxt: DeserializationContext): MyServerRequest {
        val codec = parser.codec
        val jsonNode = codec.readTree<JsonNode>(parser)
        return if (jsonNode.isArray) {
            codec.treeToValue(jsonNode, SingleRequest::class.java)
        } else {
            codec.treeToValue(jsonNode, BatchRequest::class.java)
        }
    }
}

this though fails with stackoverflow error as sealed class implementations look up the root deserializer... any ideas how to make it work?

This message was deleted.

I'm trying to construct an object from json, with some members injected via

@JacksonInject

. I've got it working like this:

class ClassToDeserialize {
    @JacksonInject
    private val dependency: ThirdPartyUndeserializableObject? = null
    @JsonPropery
    private val simpleValue: String
    /// ... etc 
}

To avoid nullability (and since I don't really have an instance of the dependency I can assign statically), I'd like to use constructor injection instead:

class ClassToDeserialize(
    @JacksonInject
    private val dependency: ThirdPartyUndeserializableObject
) {
    @JsonPropery
    private val simpleValue: String
    /// ... etc 
}

but doing so still results in jackson trying to manage the dependency prior to using the injected value (manifests as

Invalid definition for property

since the class isn't json deserializable due to conflicting setters within the third party class). Adding a

@JsonIgnore

doesn't appear to have any effect, either. Is there a way to do this?

Hi, I have an issue with Jackson, Spring Boot and Kotlin 1.5 when using value classes. The converted json key includes the “special” class name suffix generated by the kotlin compiler for value classes. E.g. for

data class Resource(
    val fooInterval: Milliseconds,
    val barInterval: Milliseconds?,
    …
)
@JvmInline
value class Milliseconds(val units: Int)

The generated json for

fooInterval

becomes

"fooInterval-kqdxTu8": 900,

And for the nullable property it becomes

"barInterval-OO-hnm0": {
        "units": 900
}

The suffix comes from the generated type (value class) but It looks like a bug that it is used as part of the parameter name. Any thoughts?

hello 👋 by any chance anyone tried conditional serialization of fields based on some condition? (I tried using custom filter as was suggested here -> https://www.baeldung.com/jackson-serialize-field-custom-criteria but with no luck). See thread for code

Does anyone know how to get Jackson CSV to honor @JsonPropertyOrder? It does need the JsonProperty attached to the getter or it'll use the field name. But it doesn't seem to honor the order despite following the technique mentioned in a few Java Stackoverflow posts....i.e., disable alphabetical ordering and use @JsonPropertyOrder. The order it's emitting is: Module,FilePath,Line,Offset,Severity,UniqueID,Category,Description,ComplexityTotal,CoverageTotal,NumBlockers,NumCriticals,NumMajors,NumMinors,NumInfos,FileCount,LinesOfCode Which bizarrely isn't alphabetical and also not the same as the definition of the data class and isn't in @JsonPropertyOrder either 🤔

Hey 👋 I had a weird behavior just now and wanted to understand it:

data class Example(@get:JsonProperty("element") val elements: List<Element> = listOf())

I remembered somehow that you need to add the get: part to a JsonProperty annotation such that it would be at the getter and not the field from Javas point of view, or else it woudn’t work right (which seems to be not the case after all), but this code above resulted in the following exception:

com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize value of type `int` from Array value (token `JsonToken.START_ARRAY`)

Now I strongly assume this is because List has a method

get

with parameter of type

Int

, but is this really how this annotation format should work? How would I even attach an annotation to the java getter in this case then? I fixed it now by removing the get:, just curious 🤔

Hello everyone, I think I had a solution for the following problem some time ago but I can’t think of one right now, so here I am: I have the following structure:

sealed class ApiResult {
    data class Error(val errors: List<ApiError>) : ApiResult() {
        data class ApiError(
            val propertyName: String,
            val errorMessage: String,
            val errorCode: String,
        )
    }
}

And I want to serialize some response json into 

ApiResult.Error

. The Json looks like that:

[
  {
    "propertyName": "...",
    "errorMessage": "...",
    "errorCode": "..."
  }
]

So I have an object with holds a list of elements. Instantiating the object manually would look like that:

ApiResult.Error(objectMapper.readValue(""))

But I want to serialize directly into

ApiResultError

. Usually I would do something along the lines of:

class ApiErrors: ArrayList<ApiErrors.ApiError>() {
        data class ApiError(
            val propertyName: String,
            val errorMessage: String,
            val errorCode: String,
        )

So, implementing the ArrayList. This does not work inside a sealed class. Any idea? Thanks in advance!

Disclaimer: This is not Kotlin specific but was hoping someone here might be able to chime in ---- Hello 👋 I have a code generator and I'm using custom Jackson serializers to support • optional serialization (so I can distinguish defined value, null value and no value cases, i.e. no value should not be serialized at all and field should be omitted) • custom object serializers/deserializers (e.g. ability to marshall/unmarshall

ULocale

object to/from basic

en_US

String) Above works fine when used in separation but now I'm trying to figure out a way to do both at the same time, i.e. conditionally serialize custom objects. Registering a module that configures custom serializer for given custom type seems to work but that also implies additional setup by the users of the library (i.e. auto generated code is used to communicate with server). Anyone has any ideas whether this setup could be automated? Or maybe there are alternatives that I could use without module registration? There is an SPI that could be used to auto register modules but its usage is supposedly discouraged....

How do I read XML lists properly from kotlin? Classes:

enum class Language {
    AmericanEnglish,
    BritishEnglish,
    Japanese,
    French,
    German,
    LatinAmericanSpanish,
    Spanish,
    Italian,
    Dutch,
    CanadianFrench,
    Russian,
    Korean,
    TraditionalChinese,
    SimplifiedChinese,
    Unknown
}

data class TitleName(
    val language: Language,
    val name: String,
    val publisher: String
)

data class NACP(
    val title: List<TitleName>,
    // TODO: Add more
)

XML (simplified):

<?xml version="1.0" encoding="utf-8"?>
<Application>
    <Title>
        <Language>AmericanEnglish</Language>
        <Name>Mario Party Superstars</Name>
        <Publisher>Nintendo</Publisher>
    </Title>
    <Title>
        <Language>BritishEnglish</Language>
        <Name>Mario Party Superstars</Name>
        <Publisher>Nintendo</Publisher>
    </Title>
    <Title>
        <Language>Japanese</Language>
        <Name>￣ﾃﾞ￣ﾃﾪ￣ﾂﾪ￣ﾃﾑ￣ﾃﾼ￣ﾃﾆ￣ﾂﾣ ￣ﾂﾹ￣ﾃﾼ￣ﾃﾑ￣ﾃﾼ￣ﾂﾹ￣ﾂ﾿￣ﾃﾼ￣ﾂﾺ</Name>
        <Publisher>Nintendo</Publisher>
    </Title>
</Application>

Code:

val parser = XmlMapper.builder()
    .addModule(
        KotlinModule.Builder()
            // Defaults
            .withReflectionCacheSize(512)
            .configure(KotlinFeature.NullToEmptyCollection, false)
            .configure(KotlinFeature.NullToEmptyMap, false)
            .configure(KotlinFeature.NullIsSameAsDefault, false)
            .configure(KotlinFeature.SingletonSupport, false)
            .configure(KotlinFeature.StrictNullChecks, false)
            .build()
    )
    // Defaults
    .configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true)
    .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
    .configure(DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES, false)
    .configure(DeserializationFeature.FAIL_ON_NUMBERS_FOR_ENUMS, false)
    .build()

parser.readValue<NACP>(xml)
// => com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `TitleName` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('AmericanEnglish')

hello 👋 has anyone tried

value class

with jackson?

fun main() {
  val string = ObjectMapper().findAndRegisterModules()
    .convertValue<Map<String, String>>(Value("any"))

  println(string)
}

@JvmInline
value class Value(val value: String)

prints

{value=any}

with jackson 2.12.5, but fails with jackson 2.13.0. error is

Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `java.util.LinkedHashMap` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('any')
 at [Source: UNKNOWN; byte offset: #UNKNOWN]

though https://github.com/FasterXML/jackson-module-kotlin/issues/464 makes me wonder if my expectation is wrong. my use case is the one marked as “broken”:

"broken": [ {"value":0}, {"value":0} ]

, though this is exactly what I want

I did some bechmarking comparing deserialization times between jackson kotlin module and marking all my data classes as @JvmRecord and using stock jackson without kotlin module. The jvm record path clearly is faster (will try to make a GH issue with more formal claims), but this is just a lazy way of putting that the kotlin module ought to be faster… any thoughts on how to approach the same speed?

👋 hey folks, does anyone have any suggestions how I'd go about debugging https://github.com/FasterXML/jackson-module-kotlin/issues/522 issue that I'm also running into? I've tried going the no-args plugin compiler route, but it still doesn't fix some of the json classes (it fixed some, but not all). The only thing that worked is turning build minification off, but now we are running into another issue where our APK is too large for Play Store. Any help/pointers are greatly appreciated

👋 Hi all, in my automated tests I’m using Jackson to deserialise responses from two different GraphQL schemas into data classes, this works fine with a separate class for each schema but I’m trying to get it working with a single class to simplify the code. The responses from both schemas have a “data” node with different fields under that, so I’ve tried applying

@JsonAlias("data")

to two fields in my class so that I can have separate data classes representing the underlying data, but this doesn’t work - the alias seems to apply to one field or the other. I’ve tried these two methods so far but neither work:

data class MyResponse(
    @JsonAlias("data")
    val dataOne: dataClassOne?,
    @JsonAlias("data")
    val dataTwo: dataClassTwo?
)

data class MyResponse(
    @JsonAlias("data")
    val dataOne: dataClassOne?, val dataTwo: dataClassTwo?
)

Is it possible to apply the alias to both fields so that the data will be deserialised to one or the other, or should I go back to using a separate class for each schema?

Hi, another question about deserialising with Jackson - is it possible to deserialise fields with unknown names? Here is an example which is part of a response which I want to deserialise:

"types": {
  "10003327": {
    "typeNumber": 11,
    "classNumber": 335,
    "display": 0,
    "max": "2000",
    "name": "My type"
  }
},

The number

10003327

could be different in each response. If I was to use the data classes below I think it would work only for this example, but in another response with a different number it wouldn’t work:

data class Response(
    val types: NumberType
)

data class NumberType(
    @JsonProperty("10003327") val typeField: Type
)

data class Type(
    val typeNumber: Int,
    val classNumber: Int,
    val display: Int,
    val max: String,
    val name: String
)

Is there a way to deserialise this completely when you don’t know what the number of the field will be, maybe with another annotation?

I'd like to have a data class parameter that gets a default value when creating a new instance from code but not when deserialising. What's the simplest way to do that? I'll add examples in the thread.

data classes annotated with @JvmRecord were deserializable in earlier jackson versions just through the plain java record support. But now it seems you need to register KotlinModule on the objectmapper. KotlinModule is slower than the plain java record deserializer so I would prefer to get that behavior back. How do I customize my objectmapper to use that deserializer?

Has anyone managed to make

@JsonValue

work when the property is nullable and the json has null as the value? Edit - I wrongly thought this was a Kotlin issue but I can't make it work in Java either so moving to https://gitter.im/FasterXML/jackson-databind?at=635675f89ee3ec22b4d9a239

Hi. We have a problem. we're serializing an IntRange from a server we want to upgrade to 1.7.20. This ads the field

end_exclusive

. We have clients which are not able to update kotlin as easily (apps in the wild). They now get the following error:

Unrecognized field "end_exclusive" (class kotlin.ranges.IntRange), not marked as ignorable (2 known properties: "start", "end"

Does anybody know of a nice work-around for this. we thought about implementing our own small dataclass on the serverside which adhers to the

IntRange

api of kotlin <= 1.7.10, but it's seems kinda hacky...

hi guys, in hope of stumping on someone already investigating the same issue, fyi I have started a thread here https://kotlinlang.slack.com/archives/C0AVAB92L/p1667582399032569 to move the inline classes support issue forward

is there a non-kotlin specific jackson channel somewhere?

can the kotlin module be configured via

application.yaml

? for example

spring:
  jackson:
    kotlin:
      null-to-empty-collection: true
      null-to-empty-map: true
      null-is-same-as-default: true

Cross Posting. If you know how replacing

kotlin-reflect

with

kotlinx-metadata-jvm

would benefit

jackson-module-kotlin

users on

Android

, please let me know. https://kotlinlang.slack.com/archives/C0B8M7BUY/p1674267151483919