So i want to deserialize a string into a `Data Single` but i

Question

So i want to deserialize a string into a `Data Single` but it fails ```sealed class Data lt T Any gt class Single lt T Any gt val single T Data lt T gt class ListOf lt T Any gt val list List lt T gt Data lt T gt ``` Could the reason for the mismatch be that the constructor parameter `single` is nullable The error message is com fasterxml jackson databind exc MismatchedInputException Cannot construct instance of `uk co whichdigital pricingengine Data$Single` although at least one Creator exists no String argument constructor factory method to deserialize from String value up and running Here is my current jsonMapper config ``` private val jsonMapper = ObjectMapper apply registerModule KotlinModule configure MapperFeature ACCEPT CASE INSENSITIVE PROPERTIES true configure DeserializationFeature FAIL ON UNKNOWN PROPERTIES false ``` UPDATE I changed the code to `Data Single` s generic parameter is nullable `class Single lt T gt val single T Data lt T gt ` but the error message didn t change

diesieben07 · Answer

With default configuration the representation for `Single` would be a JSON object ``` single lt value here gt ```

diesieben07 · Answer

If you just want the value you can use ` JsonCreator` on the constructor and ` JsonValue` on the property

Stephan Schroeder · Answer

give that this is the whole TypeDefiinition `class Single lt T gt val single T Data lt T gt ` I guess the constructor is implicit and so annotated version would be `class Single lt T gt JsonValue val single T Data lt T gt ` The error message didn t change no String argument constructor factory method to deserialize

diesieben07 · Answer

Well you haven t annotated the constructor `class Single lt T gt JsonCreator constructor JsonValue val single T Data lt T gt `

Stephan Schroeder · Answer

but now I did no change neutral face

diesieben07 · Answer

let me check this

diesieben07 · Answer

Seems like its a problem with jackson module kotlin

diesieben07 · Answer

Without that my solution works

Stephan Schroeder · Answer

without the Kotlin module i m running into problems with a data class confused ```InvalidDefinitionException Invalid type definition for type `uk co whichdigital pricingengine GraphQlResponse` Argument 0 has no property name is not Injectable can not use as Creator constructor for uk co whichdigital pricingengine GraphQlResponse annotations interface com fasterxml jackson annotation JsonCreator= com fasterxml jackson annotation JsonCreator mode=DEFAULT ``` with ```data class GraphQlResponse lt T D Data lt T gt gt JsonCreator constructor JsonValue val data Map lt String D gt JsonValue val errors List lt GraphQlError gt ```

diesieben07 · Answer

Yes seems like you need a custom deserializer to work around this

Stephan Schroeder · Answer

generic custom deserialisers fearful

Stephan Schroeder · Answer

I ll check making GraphQlResponse a normal class

diesieben07 · Answer

It s quite simple ``` class SingleDeserializer StdConverter lt String Data Single lt String gt gt override fun convert value String Data Single lt String gt return Data Single value JsonDeserialize converter = SingleDeserializer class class Single lt T Any gt JsonValue val single T Data lt T gt ```

Stephan Schroeder · Answer

actually the `data class` was fine I had to add ` JsonProperty` to the fields open mouth ` JsonProperty data val data Map lt String D gt `

Stephan Schroeder · Answer

The Data Single deserialisation works without the KotlinModule

Stephan Schroeder · Answer

So the simple case with String return value works now it d a good start Thx +1