:wave: hello hello. I'm having some trouble with ...

# http4k

[MrNiamh]

👋 hello hello. I'm having some trouble with a recursive class and generating the openapi definition. I have something like the below example:

data class FieldDTO(
    val name: String,
    val obj: ObjectField,
){
    companion object {
        val example = FieldDTO(
            name = "Field",
            obj = ObjectField.example
        )
    }
}

data class ObjectField(
    val name: String,
    val field: FieldDTO? = null,
){
    companion object {
        val example = ObjectField("obj", field = FieldDTO.example)
    }
}

The compiler obviously throws an error on the ObjectField example, but if I set the example to be ObjectField("obj", field = null) then I get an issue with NoFieldFound on generating the openapi as it doesn't like having nulls.

Tried to have a search but couldn't find much on what the best approach here is!

[Andrew O'Hara]

Can you share the code you use to configure the renderer in the contract builder?

[MrNiamh]

I'm just using the default, so like

renderer = OpenApi3(ApiInfo("Backend", "v1.0", "API"), CustomJackson())

However I was having a play around with passing in a new renderer but wasn't quite playing nicely. If you had any good examples that'd be great

[Andrew O'Hara]

The CustomJackson might be the issue. The default is OpenApiJackson which addresses the null serialization issue. You specifically need to add this to your custom jackson.

.setSerializationInclusion(NON_NULL)

[MrNiamh]

That's worked a treat, thank you very much!