Deserialize complex JSON in Kotlin - json

Question

I would like to deserialize the following JSON:
{
"participants": {
"0": {
"layout": "layout1"
}
},
"layouts": {
"layout1": {
"width": 100,
"height": 100
}
}
}
Into the following structure:
#Serializable
data class Layout(val width: Int, val height: Int)
#Serializable
data class Participant(val index: Int, val layout: Layout)
#Serializable
data class ViewData(val participants: MutableMap<Int, Participant>, val layouts: MutableMap<Int, Layout>)
What I'm particularly struggling with is how to create the correct relationship between participant's layout using the key "layout1" in the "layouts" hash.
Thanks!

Answer 1

You have to create the classes that matches the json string
data class Layout(
val width: Int,
val height: Int
)
data class Participant(
val layout: String
)
data class ViewData(
val participants: Map<String, Participant>,
val layouts: Map<String, Layout>
)
It is not possible (by default) to deserialize map<String, Any> to map<Int, Any> and it is not possible to add magical val index: Int
then create a function that will help you get layout by participant name
data class ViewData(
val participants: Map<String, Participant>,
val layouts: Map<String, Layout>
) {
fun getLayoutForParticipant(participantId: String): Layout? {
val layoutId = participants[participantId]?.layout
return layoutId?.let { layouts[it] }
}
}
val json: String = """
{
"participants": {
"0": {
"layout": "layout1"
}
},
"layouts": {
"layout1": {
"width": 100,
"height": 100
}
}
}
"""
val deserialized: ViewData = objectMapper.readValue(json, ViewData::class.java)
println(deserialized)
println(deserialized.getLayoutForParticipant("0"))
result:
ViewData(participants={0=Participant(layout=layout1)}, layouts={layout1=Layout(width=100, height=100)})
Layout(width=100, height=100)