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How to make Retrofit deserialize response to null object when the returned type is not matching the expected?

Retrofit is not deserialising correctly. Because I don't have control over backend I need my code to adapt to it, I need Retrofit to deserialize response to null when it isn't the right type. Instead it creates the object but with null value members. So instead of returning null it returns DefaultResponseResult(success=null, action=null, res=null)
This is my method (I tried fixing it with ? at Call<DefaultResponseResult?>):
#PUT("/SOMETHING/fcmtoken/")
fun registerFCMToken(#Query("fcmToken") fcmToken: String, #Query("driverID") driverID: String, #Query("dtoken") dtoken: String): Call<DefaultResponseResult?>
and in client file:
fun <T> fetch(requestCall: Call<T?>, completion: ((Result<T, Exception>) -> Unit)) {
requestCall.enqueue(object: Callback<T?> {
override fun onResponse(call: Call<T?>, response: Response<T?>) {
val responseData = response.body()
var errorLog: ErrorLog? = response.errorBody()?.let { gson.fromJson(it.charStream(), ErrorLog::class.java) }
//FOR SOME REASON RESPONSE DATA IS NOT NULL BUT IT SHOULD BE
if (responseData == null) {
completion(Failure(APIError(internalError = "Unknown")))
return
}
//THIS PRINTS DefaultResponseResult(success=null, action=null, res=null) unfortunately
printLogs(responseData.toString())
completion(Success(responseData))
}
override fun onFailure(call: Call<T?>, t: Throwable) {
printLogs("Failure")
printLogs(call.request().toString())
printLogs(t.toString())
completion(Failure(APIError(internalError = "Failure")))
}
})
}
DefaultResponseResult:
data class DefaultResponseResult(
val success: String?,
val action: String?,
val res: String?
)
ErrorLog:
data class ErrorLog(
val error: ErrorLogBody
)
data class ErrorLogBody(
val authentication: String? = null
//...
)
Request returns raw response as:
{
"error": "SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry
'ecyNabqKQjSPx-zn6Oshpd:APA91bFS7fGpnmnO_CiYfkQoF0Oo52ODWGRt-M...' for
key 'PRIMARY'" }
And retrofit doesn't recognize it as error body because http code is 200 and that's something I can't change in the backend. I expect it to cast response.body() to null because data type is ErrorLog not DefaultResponseResult, instead it does this (from logcat console):
DefaultResponseResult(success=null, action=null, res=null)
How can I make it return null instead of DefaultResponseResult?

Consuming Polymorphic Jsons with Retrofit and Kotlin

My API sends me a polyphonic Json in with the variable addon_item can be either a String or an Array, I have spend days trying to make a CustomDezerializer for it without any success.
Here is the Json response:
({
"code": 1,
"msg": "OK",
"details": {
"merchant_id": "62",
"item_id": "1665",
"item_name": "Burrito",
"item_description": "Delicioso Burrito en base de tortilla de 30 cm",
"discount": "",
"photo": "http:\/\/www.asiderapido.cloud\/upload\/1568249379-KDKQ5789.jpg",
"item_cant": "-1",
"cooking_ref": false,
"cooking_ref_trans": "",
"addon_item": [{
"subcat_id": "144",
"subcat_name": "EXTRA",
"subcat_name_trans": "",
"multi_option": "multiple",
"multi_option_val": "",
"two_flavor_position": "",
"require_addons": "",
"sub_item": [{
"sub_item_id": "697",
"sub_item_name": "Queso cheddar",
"item_description": "Delicioso queso fundido",
"price": "36331.20",
"price_usd": null
}]
}]
}
})
Here is the Custom Dezerializer, which includes BodyConverter that removes two braces that encompassed the Json response:
'''
/**
* This class was created due to 2 issues with the current API responses:
* 1. The API JSON results where encapsulated by parenthesis
* 2. They had dynamic JSON variables, where the Details variable was coming as a String
* or as an Object depending on the error message (werer whe user and password wereh correct.
*
*/
class JsonConverter(private val gson: Gson) : Converter.Factory() {
override fun responseBodyConverter(
type: Type?, annotations: Array<Annotation>?,
retrofit: Retrofit?
): Converter<ResponseBody, *>? {
val adapter = gson.getAdapter(TypeToken.get(type!!))
return GsonResponseBodyConverter(gson, adapter)
}
override fun requestBodyConverter(
type: Type?,
parameterAnnotations: Array<Annotation>?,
methodAnnotations: Array<Annotation>?,
retrofit: Retrofit?
): Converter<*, RequestBody>? {
val adapter = gson.getAdapter(TypeToken.get(type!!))
return GsonRequestBodyConverter(gson, adapter)
}
internal inner class GsonRequestBodyConverter<T>(
private val gson: Gson,
private val adapter: TypeAdapter<T>
) : Converter<T, RequestBody> {
private val MEDIA_TYPE = MediaType.parse("application/json; charset=UTF-8")
private val UTF_8 = Charset.forName("UTF-8")
#Throws(IOException::class)
override fun convert(value: T): RequestBody {
val buffer = Buffer()
val writer = OutputStreamWriter(buffer.outputStream(), UTF_8)
val jsonWriter = gson.newJsonWriter(writer)
adapter.write(jsonWriter, value)
jsonWriter.close()
return RequestBody.create(MEDIA_TYPE, buffer.readByteString())
}
}
// Here we remove the parenthesis from the JSON response
internal inner class GsonResponseBodyConverter<T>(
gson: Gson,
private val adapter: TypeAdapter<T>
) : Converter<ResponseBody, T> {
#Throws(IOException::class)
override fun convert(value: ResponseBody): T? {
val dirty = value.string()
val clean = dirty.replace("(", "")
.replace(")", "")
try {
return adapter.fromJson(clean)
} finally {
value.close()
}
}
}
class DetalleDeProductoDeserializer : JsonDeserializer<DetallesDelItemWrapper2> {
override fun deserialize(
json: JsonElement,
typeOfT: Type,
context: JsonDeserializationContext
): DetallesDelItemWrapper2 {
if ((json as JsonObject).get("addon_item") is JsonObject) {
return Gson().fromJson<DetallesDelItemWrapper2>(json, ListaDetalleAddonItem::class.java)
} else {
return Gson().fromJson<DetallesDelItemWrapper2>(json, DetallesDelItemWrapper2.CookingRefItemBoolean::class.java)
}
}
}
companion object {
private val LOG_TAG = JsonConverter::class.java!!.getSimpleName()
fun create(detalleDeProductoDeserializer: DetalleDeProductoDeserializer): JsonConverter {
Log.e("Perfill Adapter = ", "Test5 " + "JsonConverter" )
return create(Gson())
}
fun create(): JsonConverter {
return create(Gson())
}
private fun create(gson: Gson?): JsonConverter {
if (gson == null) throw NullPointerException("gson == null")
return JsonConverter(gson)
}
}
}
Here is the RetrofitClient.class:
class RetrofitClient private constructor(name: String) {
private var retrofit: Retrofit? = null
fun getApi(): Api {
return retrofit!!.create(Api::class.java)
}
init {
if (name == "detalleDelItem") run {
retrofit = Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(JsonConverterJava.create(JsonConverterJava.DetallesDelItemDeserializer()))
// .addConverterFactory(GsonConverterFactory.create(percentDeserializer))
.client(unsafeOkHttpClient.build())
.build()
Log.e("RetrofitClient ", "Instace: " + "detalle " + name)
}
}
companion object {
//Remember this shit is https for the production server
private val BASE_URL = "http://www.asiderapido.cloud/mobileapp/api/"
private var mInstance: RetrofitClient? = null
#Synchronized
fun getInstance(name: String): RetrofitClient {
mInstance = RetrofitClient(name)
return mInstance!!
}
}
}
Finally my POJO:
open class DetallesDelItemWrapper2 {
#SerializedName("code")
val code: Int? = null
#Expose
#SerializedName("details")
var details: ItemDetails? = null
#SerializedName("msg")
val msg: String? = null
class ItemDetails {
#Expose
#SerializedName("addon_item")
val addonItem: Any? = null
#SerializedName("category_info")
val categoryInfo: CategoryInfo? = null
#SerializedName("cooking_ref")
val cookingRef: Any? = null
#SerializedName("cooking_ref_trans")
val cookingRefTrans: String? = null
}
class ListaDetalleAddonItem: DetallesDelItemWrapper2(){
#SerializedName("addon_item")
val detalleAddonItem: List<DetalleAddonItem>? = null
}
class StringDetalleAddonItem: DetallesDelItemWrapper2(){
#SerializedName("addon_item")
val detalleAddonItem: String? = null
}

I took a shot at this and came up with 2 possible ideas. I don't think they're the only way to achieve this, but I think I can share my thoughts.
First, I've reduced the problem to actually only parsing the items. So I've removed retrofit from the equation and use the following jsons:
val json = """{
"addon_item": [{
"subcat_id": "144",
"subcat_name": "EXTRA",
"subcat_name_trans": "",
"multi_option": "multiple",
"multi_option_val": "",
"two_flavor_position": "",
"require_addons": "",
"sub_item": [{
"sub_item_id": "697",
"sub_item_name": "Queso cheddar",
"item_description": "Delicioso queso fundido",
"price": "36331.20",
"price_usd": null
}]
}]
}
""".trimIndent()
(for when the addon_item is an array)
val jsonString = """{
"addon_item": "foo"
}
""".trimIndent()
(for when the addon_item is a string)
First approach
My first approach was to model addon_item as a generic JsonElement:
data class ItemDetails(
#Expose
#SerializedName("addon_item")
val addonItem: JsonElement? = null
)
(I'm using data classes because I find them more helpful, but you don't have too)
The idea here is to let gson deserialize it as a generic json element and you can then inspect it yourself. So if we add some convenience methods to the class:
data class ItemDetails(
#Expose
#SerializedName("addon_item")
val addonItem: JsonElement? = null
) {
fun isAddOnItemString() =
addonItem?.isJsonPrimitive == true && addonItem.asJsonPrimitive.isString
fun isAddOnItemArray() =
addonItem?.isJsonArray == true
fun addOnItemAsString() =
addonItem?.asString
fun addOnItemAsArray() =
addonItem?.asJsonArray
}
So as you can see, we check the addOnItem for what it contains and according to that, we can obtain its contents. Here's an example of how to use it:
fun main() {
val item = Gson().fromJson(jsonString, ItemDetails::class.java)
println(item.isAddOnItemArray())
println(item.isAddOnItemString())
println(item.addOnItemAsString())
}
I think the biggest advantage of this is that it's fairly simple and you don't require custom logic to deserialize. For me, the huge drawback is the type-safety loss.
You can get the add on as an array, but it will be an array of json elements that have to be "manually" deserialized. Hence, my 2nd approach tries to tackle this.
Second approach
The idea here is to use Kotlin's sealed classes and have 2 types of add ons:
sealed class AddOnItems {
data class StringAddOnItems(
val addOn: String
) : AddOnItems()
data class ArrayAddOnItems(
val addOns: List<SubCategory> = emptyList()
) : AddOnItems()
fun isArray() = this is ArrayAddOnItems
fun isString() = this is StringAddOnItems
}
The SubCategory class is just what was inside the list. Here's a simple version of it:
data class SubCategory(
#SerializedName("subcat_id")
val id: String
)
As you can see the AddOnItems is a sealed class that has the only 2 possible types for your use case.
Now we need a custom deserializer:
class AddOnItemsDeserializer : JsonDeserializer<AddOnItems> {
override fun deserialize(json: JsonElement?, typeOfT: Type?, context: JsonDeserializationContext?) =
when {
json?.isJsonArray == true -> {
AddOnItems.ArrayAddOnItems(context!!.deserialize(
json.asJsonArray,
TypeToken.getParameterized(List::class.java, SubCategory::class.java).type))
}
json?.isJsonPrimitive == true && json.asJsonPrimitive.isString ->
AddOnItems.StringAddOnItems(json.asJsonPrimitive.asString)
else -> throw IllegalStateException("Cannot parse $json as addonItems")
}
}
In a nutshell, this checks if add on is an array and creates the respective class and the same for string.
Here's how you can use it:
fun main() {
val item = GsonBuilder()
.registerTypeAdapter(AddOnItems::class.java, AddOnItemsDeserializer())
.create()
.fromJson(jsonString, ItemDetails::class.java)
println(item.addOnItems.isString())
println(item.addOnItemsAsString().addOn)
val item = GsonBuilder()
.registerTypeAdapter(AddOnItems::class.java, AddOnItemsDeserializer())
.create()
.fromJson(json, ItemDetails::class.java)
println(item.addOnItems.isArray())
println(item.addOnItemsAsArray().addOns[0])
}
I think the biggest advantage here is that you get to keep the types. However, you still need to check what it is before calling addOnItemsAs*.
Hope this helps

retrofit - kotlin - Parameter specified as non-null is null

I'm using mvvm , kotlin , retrofit and courtin in my app . I've done several request and all of them works fine but with this one , I get this error "Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter list"
this is my json
{
"roomslist": [
{
"id": "1"
}
]
}
these are my models
data class RoomsListModel(
#Json(name = "roomslist")
val roomsList: List<Rooms>
)
data class Rooms(
#Json(name = "id")
val id: String
}
this is my api interface :
#FormUrlEncoded
#POST("getPlaceRooms.php")
fun getPlaceRooms2(#Field("amlakid")id:String):Deferred<RoomsListModel>
this is my repository :
fun getRooms(
amlakId: String
): MutableLiveData<RoomsListModel> {
scope.launch {
val request = api.getPlaceRooms2(amlakId)
withContext(Dispatchers.Main) {
try {
val response = request.await()
roomsLiveData.value = response
} catch (e: HttpException) {
Log.v("this", e.message);
} catch (e: Throwable) {
Log.v("this", e.message);
}
}
}
return roomsLiveData;
}
when the app runs , it goes into e: Throwable and returns the error
my viewmodel
class PlacesDetailsViewModel : ViewModel() {
private val repository = PlaceDetailsRepository()
fun getRooms(amlakId: String):MutableLiveData<RoomsListModel> {
return repository.getRooms(amlakId)
}
}
and this my activity request :
viewModel.getRooms(amlakId).observe(this, Observer {
vf.frm_loading.visibility = View.GONE
it?.let {
adapter.updateList(it?.roomsList)
setNoItem(false)
}
})
I'm using moshi
I've tried to clean ,rebuild but it doesn't make any different
could you help me ?
what is going wrong with my code?

You should try adding ? to your Model parameters. Not sure if in your case is the String?. It will ensure that you can have null values on your String
val id: String?
Please double check, whatever value is missing or null in your case

Have you tried removing #Json annotation in your val id: String declaration?

How to properly make reusable class to catch response data using retrofit?

I am new in Android development, and I am trying to get data from server. the general JSON response structure will be like this
{
"success": "1",
"data": [
{
"customers_id": 4,
"customers_gender": "0",
"customers_firstname": "TES IOS",
"customers_lastname": "TES IOS",
"customers_dob": "2018-12-27",
"email": "TES002#email.com",
"user_name": "TES002",
"customers_default_address_id": 0,
"customers_telephone
},
"message": "Successfully get user data from server"
}
the "success" and "message" field will be the same (will always be string). but the "data" can be different for other request call. It can send user data, store data or product data, or even Array/List of Products.
so I want to make general reusable class to catch that JSON response. the class will be like this, I set the "data" to be Any, and then later it will be casted back to User object:
class ServerData(successStatus: Int, data: Any, message: String) {
val isSuccessfull : Boolean
val data : Any
val message : String
init {
isSuccessfull = successStatus != 0
this.data = data
this.message = message
}
}
the interface is like this:
interface LakuinAPI {
#FormUrlEncoded
#POST("processlogin")
fun performLogin(
#Field("kode_customer") outletCode: String,
#Field("password") password: String
): Call<ServerData>
}
and then I use it in the activity, like the code below:
private fun sendLoginDataToServer(outletCode: String, password: String) {
val call = lakuinAPI.performLogin(outletCode,password)
call.enqueue(object: Callback<ServerData> {
override fun onFailure(call: Call<ServerData>, t: Throwable) {
Toast.makeText(this#LoginActivity,t.localizedMessage,Toast.LENGTH_LONG).show()
}
override fun onResponse(call: Call<ServerData>, response: Response<ServerData>) {
if (!response.isSuccessful) {
Toast.makeText(this#LoginActivity,"Code: " + response.code(),Toast.LENGTH_LONG).show()
return
}
val lakuinServerData = response.body()
val userList = lakuinServerData?.data as List<User> // the error in here
val userData = userList.first() // the error in here
println(userData)
}
})
}
but I get error message:
java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap
cannot be cast to com.ssss.lakuinkotlin.Model.User
I give comment in the code above the location of the error. I don't why it happened.
to be honest, I am not if this is the correct way to catch user data from general response JSON like the the JSON above. is there a better way ?

You can use generics to achieve it
class Response<Data> constructor() : ResponseSimple() {
#SerializedName(FIELD_DATA)
var data: Data? = null
private constructor(data: Data) : this() {
this.data = data
}
companion object {
const val FIELD_SUCCESS = "success"
const val FIELD_ERROR = "error"
const val FIELD_DATA = "data"
const val FIELD_MESSAGE = "message"
#JvmStatic
fun <Data> create(data: Data): Response<Data> {
return Response(data)
}
}
}
And ResponseSimple is
open class ResponseSimple {
#SerializedName(Response.FIELD_ERROR)
var error: String = ""
#SerializedName(Response.FIELD_SUCCESS)
var succes: Boolean = false
#SerializedName(Response.FIELD_MESSAGE)
var message:String = ""
}
Then api response should be Call<Response<ServerData>>.
And about ClassCastException, you can't convert ServerData to User just using as.
You need to use Call<Response<ArrayList<User>>> or create class converter.

Try replacing this line :
val userList = lakuinServerData?.data as List<User>
with:
val userList = lakuinServerData?.data as new TypeToken<List<User>>(){}.getType()

How to get Json Response in Arraylist from List<Item> using RxJava and Kotlin

Facing Problem on getting Response in ArrayList.
I have following Respose on String value
var res_message: String = ""
res_message = "${result.vehicletypes} "
Getting below Value on this String
[VehicleType(_id=1, vehicleType=Hatchback, __v=0),
VehicleType(_id=2, vehicleType=Maruti, __v=0),
VehicleType(_id=3, vehicleType=Honda, __v=0),
VehicleType(_id=4, vehicleType=Bike, __v=0)]
Retrofit Result is
vehicletypes = {ArrayList#6055} size = 4
0 = {Model$VehicleType#6058} "VehicleType(_id=1,
vehicleType=Hatchback, __v=0)"
1 = {Model$VehicleType#6059} "VehicleType(_id=2,
vehicleType=Maruti, __v=0)"
2 = {Model$VehicleType#6060} "VehicleType(_id=3,
vehicleType=Honda, __v=0)"
3 = {Model$VehicleType#6061} "VehicleType(_id=4,
vehicleType=Bike, __v=0)"
Below Code snippest sending request to API.
disposable = apiServices.getVehicle(token)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(
{ result ->
res_message = "${result.vehicletypes} "
Log.d("Type==", res_message)
},
{ error ->
res_message = "${error.message}"
// validateToken()
}
)
Model Class
data class Vehicles(val success: Boolean, val vehicletypes: List<VehicleType>, val message: String)
data class VehicleType(val _id: String, val vehicleType: String, val __v: String)
I want to get this value on Arralist VehicleType List on below vehicleListArray
private var vehicleListArray: ArrayList<Model.VehicleType>? = null
How we can achieve this.
Thanks in advance.

Assuming that what you are trying to parse is a response from a service that is able to send you propper format for lists (eg Json) than
Retrofit can handle parsing lists with ease.
In your apiService definition:
fun getPeople(token: Whatever): Observable<List<VehicleType>>
And if you don't have it already:
Retrofit.Builder()
.addConverterFactory(GsonConverterFactory.create(gson))

I got solution I have to handle Respose as below code snippet.
private fun getVehicleType() {
disposable?.add(apiServices.getVehicle(token)
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
.subscribe(this::handleResponse, this::handleError))
}
private fun handleResponse(vehicles: Model.Vehicles) {
VehiclesArrayList = ArrayList(vehicles.vehicletypes)
Log.d("type==","n--"+VehiclesArrayList )
mAdapter = DataAdapter(VehiclesArrayList !!, this)
v_android_list.adapter = mAdapter
}
private fun handleError(error: Throwable) {
Log.d("type", error.localizedMessage)
Toast.makeText(context, "Error ${error.localizedMessage}", Toast.LENGTH_SHORT).show()
}