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Formatting the Nested JSON response from retrofit API in MVVM Architecture - Kotlin

I m new to kotlin and MVVM, I have been working around this issue for a week now, couldn't get any idea even after searching for some code on the internet.
I'm trying to edit or modify the retrofit response (to observe a specific type; say "sf") according to my need and neglecting other data which is not needed. I'm using mutable livedata to fetch and update the JSON data from the retrofit response to the recylerview.
Here is the link for the JSON data: http://www.nactem.ac.uk/software/acromine/dictionary.py?sf=HMM
3 Data classes based on JSON response:
data class sf(
#SerializedName("sf")
#Expose
val sf : String? = null,
#SerializedName("lfs")
#Expose
val lfs : List<lfs>? = null,
)
data class lfs(
#SerializedName("lf")
#Expose
var lf : String? = null,
#SerializedName("freq")
#Expose
var freq : Int? = null,
#SerializedName("since")
#Expose
var since : Int? = null,
#SerializedName("vars")
#Expose
var vars : List<vars>? = null,
) : Serializable
class vars (
#SerializedName("lf")
#Expose
var lf : String? = null,
#SerializedName("freq")
#Expose
var freq : Int? = null,
#SerializedName("since")
#Expose
var since : Int?
): Serializable
Code in Activity:
listUsers = mutableListOf()
adapter = WordAdapters(this, listUsers )
recyclerView.adapter = adapter
wordViewModel = ViewModelProviders.of(this,
WordViewModelFactory(this)).get(WordsViewModel::class.java)
wordViewModel!!.getData().observe(this, { t: ArrayList<sf>? ->
listUsers.clear()
t?.let { listUsers.addAll(it)
}
adapter.notifyDataSetChanged()
})
ViewModel:
class WordsViewModel ( context: Context) : ViewModel() {
private var listData = MutableLiveData<ArrayList<sf>>()
init {
val wordRepository: WordsRepository by lazy {
WordsRepository
}
//if (context.isInternetAvailable()) {
listData = wordRepository.getMutableLiveData(context)
// }
}
fun getData(): MutableLiveData<ArrayList<sf>> {
return listData
} }
Repository:
object WordsRepository {
var call: Call<MutableList<sf>>? = null
fun getMutableLiveData(context: Context) : MutableLiveData<ArrayList<sf>> {
val mutableLiveData = MutableLiveData<ArrayList<sf>>()
//context.showProgressBar()
call = NetworkApiClient.apiService.getWordsMatching("HMM")
call!!.enqueue(object : Callback<MutableList<sf>> {
override fun onFailure(call: Call<MutableList<sf>>, t: Throwable) {
//hideProgressBar()
Log.e("error", t.localizedMessage.toString())
}
override fun onResponse(call: Call<MutableList<sf>>, response:
Response<MutableList<sf>>)
{
//hideProgressBar()
if (!response.isSuccessful){
Log.e("Code " , response.code().toString());
return
}
val raw: okhttp3.Response = response.raw()
val usersResponse : MutableList<sf>? = response.body()
/* if (usersResponse != null) {
for( movie in usersResponse[0].lfs!!){
Log.v("MainActivity", movie.vars.toString())
}
}*/
Log.e("Output : ", usersResponse.toString())
usersResponse?.let { mutableLiveData.value = it as ArrayList<sf> }
}
})
return mutableLiveData
}
}
this is the base structure of JSON: here "sf" is a string, lfs is the array, according to this JSON response link provided I get 8 lfs arrays, but currently after parsing the recyclecount is 1 which is the same in the adapter itemcount method, so I get one row displayed in recylerview and rest are ignored.
JSON response:
[
{
"sf":"HMM",
"lfs":[
{
"lf":"heavy meromyosin",
"freq":267,
"since":1971,
"vars":[
{
"lf":"heavy meromyosin",
"freq":244,
"since":1971
},
{
"lf":"Heavy meromyosin",
"freq":12,
"since":1975
},
{
"lf":"H-meromyosin",
"freq":5,
"since":1975
},
{
"lf":"heavy-meromyosin",
"freq":4,
"since":1977
},
{
"lf":"heavy meromyosin",
"freq":1,
"since":1976
},
{
"lf":"H-Meromyosin",
"freq":1,
"since":1976
}
]
},
I want to ignore "sf" string after response and parse the ArrayList which is present under the "sf" which is "lfs", so based on "lfs" I need to display the data.
Mutable live data is not accepting any other type other than sf, since I placed the observer on it.

On the json you posted, there is only one parent item ( one sf ), but you are actually trying to pass the 8 lfs children. You have to perform such transformation somewhere, it could be on the network call directly, like this:
usersResponse?.let { mutableLiveData.value = it[0].lfs as ArrayList }
Take into account two things:
It could be better to check if "it" is not empty before going for the first item.
This only works if you will always have only one item on the parent array ( this sounds strange since if this is the case then the service should be returning an object, not a list, as the root of the json. If you will receive more than one object you will have to map the response into a single list of lfs. Something like (pseudo code since I'm from my phone):
It.map( item -> item.lfs)

How to convert similar Json objects to Json Arrays with Gson and Retrofit

Let's say I'm getting below response from API
{"success":true,
"base":"EUR",
"date":"2021-04-16",
"rates":
{"AED":4.393943,"AFN":92.83145,"ALL":123.125765,"AMD":621.059723}}
and I want the last rates object to be a List of Rate class i.e. Rate(code="AED", value="4.393943"). I am using Retrofit and Gson. I know I need a Deserializer or a Type Adapter. I just don't know how to write one.
Rate Class:
data class Rate(
val code:String,
val value:Float
)
Currency Class:
data class Currency(
#SerializedName("success")
val success: Boolean?,
#SerializedName("base")
val base: String?,
#SerializedName("date")
val date: Date?,
#SerializedName("rates")
val rates: List<Rate>?
)
This is the request:
val gson: Gson = GsonBuilder()
.registerTypeHierarchyAdapter(Rate::class.java, TypeAdapterOrDeserializer())
.create()
val retrofit = Retrofit.Builder()
.baseUrl("https://api.exchangerate.host")
.addConverterFactory(GsonConverterFactory.create(gson))
.build()
val jsonPlaceholderApi = retrofit.create(JsonPlaceholderApi::class.java)
val call = jsonPlaceholderApi.currency
When I request data from api it gives this error, I know why ;) as I have given List of Rates in Currency class but it is a json rate object.
com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT
Thank you for the help :)

The data for rates returned by the API is a JSON object, but in your data class you defined it as a List so Gson expects it to be a JSON array. You would need custom parsing for your Currency class in this case.
Use this deserializer:
class CurrencyDeserializer : JsonDeserializer<Currency> {
override fun deserialize(json: JsonElement?, typeOfT: Type?, context: JsonDeserializationContext?): Currency {
if (json == null || context == null) {
// handle error here
throw Exception("Error")
}
val obj = json.asJsonObject
// let Gson handle the other 3 properties
val success = context.deserialize<Boolean?>(obj.get("success"), Boolean::class.java)
val base = context.deserialize<String?>(obj.get("base"), String::class.java)
val date = context.deserialize<Date?>(obj.get("date"), Date::class.java)
// create List<Rate> from the rates JsonObject
val ratesSet = obj.get("rates").asJsonObject.entrySet()
val ratesList = ratesSet.map {
val code = it.key
val value = it.value.asFloat
Rate(code, value)
}
return Currency(success, base, date, ratesList)
}
}
Add it to Gson like this:
val gson: Gson = GsonBuilder()
.registerTypeAdapter(Currency::class.java, CurrencyDeserializer())
.create()

How do I include the DOCTYPE declaration when serializing to XML using Retrofit2 and SimpleXmlConverterFactory?

I'm trying to use SimpleXmlConverterFactory with Retrofit to create an XML request to a REST service. However, the service requires the DTD declaration in the request like so.
<!DOCTYPE paymentService PUBLIC "-//WorldPay//DTD WorldPay PaymentService v1//EN" "http://dtd.worldpay.com/paymentService_v1.dtd">
But when SimpleXmlConverterFactory serializes the data objects, it leaves off the DOCTYPE declaration:
<paymentService merchantCode="..." version="1.4">
<inquiry>
<shopperTokenRetrieval>
<authenticatedShopperID>...</authenticatedShopperID>
</shopperTokenRetrieval>
</inquiry>
</paymentService>
Creating the SimpleXmlConverterFactory isn't anything special:
val builder = Retrofit
.Builder()
.addConverterFactory(
SimpleXmlConverterFactory.create()
)
.baseUrl(BuildConfig.WORLDPAY_BASE_URL)
.build()
.create(WorldPayApiService::class.java)
And here is the annotated data object
#Root(name = "paymentService")
data class WorldPayXmlPaymentService(
#field:Attribute(name = "version")
var version: String = "",
#field:Attribute(name = "merchantCode")
var merchantCode: String = "",
#field:Element(name = "reply", required = false)
var reply: WorldPayXmlReply? = null,
#field:Element(name = "inquiry", required = false)
var inquiry: WorldPayXmlInquiry? = null
)

I added an override of a Persister as a parameter to the SimpleXmlConverterFactory.create method, like the following. It looks for the root element and then outputs the DOCTYPE before serializing the rest.
val persister = object : Persister() {
#Throws(Exception::class)
override fun write(source: Any, out: Writer) {
(source as? WorldPayXmlPaymentService)?.let {
val docType = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" +
"<!DOCTYPE paymentService PUBLIC \"-//WorldPay//DTD WorldPay PaymentService v1//EN\" \"http://dtd.worldpay.com/paymentService_v1.dtd\">"
out.write(docType)
super.write(source, out)
}
}
}
val builder = Retrofit
.Builder()
.addConverterFactory(
SimpleXmlConverterFactory.create(persister)
)
.baseUrl(BuildConfig.WORLDPAY_BASE_URL)
.build()
.create(WorldPayApiService::class.java)
where WorldPayXmlPaymentService is my root data object.
Thanks to #CommonsWare for the guidance.

How to get GSON & Retrofit to serialize and map an array from a JSON response into a String?

I am making an API request which returns some array values. I need to serialize these array values so that I can assign them to their corresponding class attributes (which are String types).
Now I know how to use GSON to serialize and deserialize lists, but with Retrofit the mapping is done automatically. This means that if my attribute is of type String, the API call returns the error "Expected a String but received an Array instead". How do I get around this so that I can receive them as arrays without failure, and them store them as strings subsequently?
My API Response:
{
"utterances": [{
"langs": ["eng", "afr", "xho", "zul"],
"utts": [
"Have you been here before?",
"Was u al hier gewees?",
"Ingaba wakhe weza apha ngaphambili?",
"Ingabe uke weza lapha ngaphambilini?"
],
"responses": [
["Yes", "No"],
["Ja", "Nee"],
["Ewe", "Hayi"],
["Yebo", "Cha"]
]
},
{
"langs": ["eng", "afr", "xho", "zul"],
"utts": [
"How are you?",
"Hoe gaan dit met jou?",
"unjani?",
"unjani?"
],
"responses": [
["Good", "Bad"],
["Goed", "sleg"],
["ezilungileyo", "ezimbi"],
["kuhle", "kubi"]
]
}
]
}
My UtteranceResponse class:
class UtteranceResponse {
#SerializedName("status")
var status: String? = null
#SerializedName("count")
var count: Int = 0
#SerializedName("utterances")
var utterances: ArrayList<Utterance>? = null
}
My Utterance class:
class Utterance: SugarRecord {
#SerializedName ("langs")
var langs: String? = null
#SerializedName ("utts")
var utterances_text: String? = null
var utterances_tts: String? = null
#SerializedName ("responses")
var responses_text: String? = null
constructor(){
}
}
And finally the calling function:
fun getUtterancesFromWebservice (){
val apiService = ApiInterface.create()
val call = apiService.getUtteranceDetails()
call.enqueue(object: Callback<UtteranceResponse> {
override fun onResponse(call: Call<UtteranceResponse>, response: retrofit2.Response<UtteranceResponse>?) {
if (response != null) {
if (response.body()?.utterances != null){
var list: List<Utterance> = response.body()?.utterances!!
val utterances: Utterance = list[0]
//storeUtterancesFromList(list)
} else {
Log.d ("Response:", response.body().toString())
}
}else{
Log.d ("responseResult", "NULL")
}
}
override fun onFailure(call: Call<UtteranceResponse>, t: Throwable) {
Log.e("SHIT", t.toString())
}
})
}
UPDATE
My API Interface as well:
#GET("bins/1ahazo")
abstract fun getUtteranceDetails():Call<UtteranceResponse>
companion object Factory {
const val BASE_URL = "https://api.myjson.com/"
fun create(): ApiInterface {
val gson = GsonBuilder().setPrettyPrinting().create()
val retrofit = Retrofit.Builder()
.baseUrl(BASE_URL)
.addConverterFactory(GsonConverterFactory.create())
.build()
return retrofit.create(ApiInterface::class.java)
}
}

You are returning single object not list. Change Call<UtteranceResponse> in ApiInterface to
Call<List<Utterance>>
and for converting list to string list to string and string to list
class Utterance: SugarRecord {
#SerializedName ("langs")
var langs: List<String?>? = null
#SerializedName ("utts")
var utterances_text: String? = null
var utterances_tts: List<String?>? = null
#SerializedName ("responses")
var responses_tex:List<List<String?>?>? = null;
constructor(){
}
}

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()
}