Convert JSON to Kotlin Model class Using GSON, in 5 seconds, Android | Kotlin

 As a Native android developer, it is very difficult to parse a complex JSON in our application. Normally the rest api json structure is much complex to parse it using functions as getObject(), getString(), getBoolean() etc.

So, In order to overcome this problem also for save time we use GSON. Many developers already know that, but here I give you a simple and short solution that, you can convert JSON to Kotlin Model class for any complex JSON within 5 seconds. So Just follow the guidelines-

Okay, First you can add the gradle dependency of GSON

implementation 'com.google.code.gson:gson:2.8.6'

Now I can take a sample JSON, which I make model class and then parse. Below I mentioned the sample json-

{
  "problems": [
    {
      "Diabetes": [
        {
          "medications": [
            {
              "medicationsClasses": [
                {
                  "className": [
                    {
                      "associatedDrug": [
                        {
                          "name": "asprin",
                          "dose": "",
                          "strength": "500 mg"
                        }
                      ],
                      "associatedDrug2": [
                        {
                          "name": "somethingElse",
                          "dose": "",
                          "strength": "500 mg"
                        }
                      ]
                    }
                  ],
                  "className2": [
                    {
                      "associatedDrug": [
                        {
                          "name": "asprin",
                          "dose": "",
                          "strength": "500 mg"
                        }
                      ],
                      "associatedDrug2": [
                        {
                          "name": "somethingElse",
                          "dose": "",
                          "strength": "500 mg"
                        }
                      ]
                    }
                  ]
                }
              ]
            }
          ],
          "labs": [
            {
              "missing_field": "missing_value"
            }
          ]
        }
      ],
      "Asthma": [
        {
          
        }
      ]
    }
  ]
}

Now, Open Android Studio and create a project. 

Now open File->Settings->Plugins and search "JSON to Kotlin Class". Install the plugin and restart your android studio.

Now Simply you can open your project and create a kotlin class, sat 'JsonResponse.kt'. Now open the class and use "Alt +K" and a popup is opened. Now you can paste your JSON in this Form and set name "Response"

Now click on "Advance" button and set the setting as per below screenshots

Setting Property

Setting Annotation

Setting Others

Setting Extensions

Now click on OK, and in first pop-up click "Generate". Now your Kotlin class is ready.

it is your generated class

package com.example.adaptermaker

import androidx.annotation.Keep

import com.google.gson.annotations.SerializedName


class JsonResponse {

    @Keep
    data class Response(
        @SerializedName("problems")
        val problems: List<Problem>
    )

    @Keep
    data class Problem(
        @SerializedName("Asthma")
        val asthma: List<Asthma>,
        @SerializedName("Diabetes")
        val diabetes: List<Diabete>
    )

    @Keep
    class Asthma

    @Keep
    data class Diabete(
        @SerializedName("labs")
        val labs: List<Lab>,
        @SerializedName("medications")
        val medications: List<Medication>
    )

    @Keep
    data class Lab(
        @SerializedName("missing_field")
        val missingField: String
    )

    @Keep
    data class Medication(
        @SerializedName("medicationsClasses")
        val medicationsClasses: List<MedicationsClasse>
    )

    @Keep
    data class MedicationsClasse(
        @SerializedName("className")
        val className: List<ClassName>,
        @SerializedName("className2")
        val className2: List<ClassName2>
    )

    @Keep
    data class ClassName(
        @SerializedName("associatedDrug")
        val associatedDrug: List<AssociatedDrug>,
        @SerializedName("associatedDrug2")
        val associatedDrug2: List<AssociatedDrug2>
    )

    @Keep
    data class ClassName2(
        @SerializedName("associatedDrug")
        val associatedDrug: List<AssociatedDrugX>,
        @SerializedName("associatedDrug2")
        val associatedDrug2: List<AssociatedDrug2X>
    )

    @Keep
    data class AssociatedDrug(
        @SerializedName("dose")
        val dose: String,
        @SerializedName("name")
        val name: String,
        @SerializedName("strength")
        val strength: String
    )

    @Keep
    data class AssociatedDrug2(
        @SerializedName("dose")
        val dose: String,
        @SerializedName("name")
        val name: String,
        @SerializedName("strength")
        val strength: String
    )

    @Keep
    data class AssociatedDrugX(
        @SerializedName("dose")
        val dose: String,
        @SerializedName("name")
        val name: String,
        @SerializedName("strength")
        val strength: String
    )

    @Keep
    data class AssociatedDrug2X(
        @SerializedName("dose")
        val dose: String,
        @SerializedName("name")
        val name: String,
        @SerializedName("strength")
        val strength: String
    )
}

Create a kotlin class, say MyJsonParser.kt and write the below code

package com.example.adaptermaker

import com.google.gson.Gson
import kotlin.reflect.KClass

class MyJsonParser {

    companion object {

        fun <T : Any> getObjectFromJson(jsonBody: String, classType: KClass<T>): T {
            return Gson().fromJson(jsonBody, classType.java)
        }

        fun Any?.convertJson() = Gson().toJson(this)

    }
}

mmmmmmmmmmmmmmmmmmmmmm

"getObjectFromJson" this function is used to convert JSON to Model Class and "convertJson" function is used it for reverse. i.e Model to JSON.

Finally, I show you my MainActivity that how to parse the json

MainActivity.kt

package com.example.adaptermaker

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import com.example.adaptermaker.MyJsonParser.Companion.convertJson
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {


    private val sampleJson =
        """{"problems":[{"Diabetes":[{"medications":[{"medicationsClasses":[{"className":[{"associatedDrug":[{"name":"asprin","dose":"","strength":"500 mg"}],"associatedDrug2":[{"name":"somethingElse","dose":"","strength":"500 mg"}]}],"className2":[{"associatedDrug":[{"name":"asprin","dose":"","strength":"500 mg"}],"associatedDrug2":[{"name":"somethingElse","dose":"","strength":"500 mg"}]}]}]}],"labs":[{"missing_field":"missing_value"}]}],"Asthma":[{}]}]}"""


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //Convert Json to Model
        val mResponse = MyJsonParser.getObjectFromJson(sampleJson, JsonResponse.Response::class)

        btnParseJson.setOnClickListener {

            //Convert Json to Model


            //As per my sample json, suppose I want to fetch
            //Diabetes->medications->medicationsClasses->className->associatedDrug->name
            val drugName =
                mResponse.problems[0].diabetes[0].medications[0].medicationsClasses[0].className[0].associatedDrug[0].name

            Toast.makeText(this, drugName, Toast.LENGTH_SHORT).show()
        }


        btnConvertJson.setOnClickListener {

            //Convert Model to JSON
            val mJson = mResponse.convertJson()

            Toast.makeText(this, mJson, Toast.LENGTH_SHORT).show()
        }


    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/btnParseJson"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Parse Json"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btnConvertJson"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="5dp"
        android:text="Convert Json"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btnParseJson" />

</androidx.constraintlayout.widget.ConstraintLayout>

Json to Model Class

Model class to Json Convert

You can download full source code here

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