JsonDeserializer

data class Student(
  var name: String? = null, 
  var address: String? = null) {
}
class StudentDeserializer : JsonDeserializer<Student> {

    override fun deserialize(json: JsonElement, typeOfT: Type, context:     JsonDeserializationContext): Student {
        json as JsonObject

        val name = json.get("name").asString
        val addressJson = json.get("address")
        val address = if (addressJson.isJsonObject) addressJson.asJsonObject.toString() else addressJson.asString

        return Student(name, address)
    }
}