Kotlin Gson parsing Json Object and Array - arrays

Question

I am pretty new to Kotlin and Json and on my work I use GSON to parse the Json.
I need to parse the following Json file into a Class by using GSON.
{
"apiKey": "blablabla",
"baseUrl": "blablabla",
"requestData": [
{
"lng": "6.971",
"lat": "50.942",
"rad": "1.5",
"type": [
"diesel",
"super"
]
},
{
"lng": "6.442",
"lat": "51.180",
"rad": "1.5",
"type": [
"diesel",
"super"
]
},{
"lng": "7.136",
"lat": "50.991",
"rad": "1.5",
"type": [
"diesel",
"super"
]
}
]
}
Now I tried to make a data class like this:
data class ApiParameterData(
var apiKey: String? = null,
var baseUrl: String? = null,
var requestData: String? = null) {
}
I also made another class to store the Json informations in it like this:
class Tankstelle: JsonDeserializer<ApiParameterData> {
override fun deserialize(json: JsonElement?, typeOfT: Type?, context: JsonDeserializationContext?
): ApiParameterData {
json as JsonObject
val apiKey = json.get("apiKey").asString
val baseUrl = json.get("baseUrl").asString
val requestDataJson = json.get("requestData")
val requestData = if (requestDataJson.isJsonObject) requestDataJson.asJsonObject.toString() else requestDataJson.toString()
return ApiParameterData(apiKey, baseUrl, requestData)
}
}
I tried to call it like that:
val gsonConfig = GsonBuilder().registerTypeAdapter(ApiParameterData::class.java, Tankstelle()).create()
val tanke = gsonConfig.fromJson(readJson, ApiParameterData::class.java)
println(tanke.requestData?.get(0))
But of course the output I get is "[" . I think because I get back a String or something and this is the first symbol of it?
I need to loop trough the requestData list and store it as a instance of a class and need to access each different value.
The thing is that I want to give the Json file different places and ranges it should look for gasstations. By reading the Json it should take all the pieces and create a link for each place I write in the requestData list. So in this case I would need 3 different links at the end. But this is another part I can do myself. I just don't know how to parse it so I can access and store every value in this Json.
Thank you already and have a great weekend!
If you need more informations just let me know

Answer 1

First you need to define two types that map to your JSON structure
class ApiParameterData(
val apiKey: String,
val baseUrl: String,
val requestData: List<RequestObject>
)
class RequestObject(
val lng: String,
val lat: String,
val rad: String,
val type: List<String>
)
Now simply parse it as
val apiData = Gson().fromJson(readJson, ApiParameterData::class.java) // No need to add TypeAdapter
// To get requestData
val requestData = apiData.requestData
requestData.forEach {
print("${it.lng}, ${it.lat}, ${it.rad}, ${it.type})
}