Android Kotlin GSON FROM (JSON > Model)

In the previous tutorial we have seen json parsing manaully without using any library , when the length of json increase it becomes very diffcult to write parsing manaully and also cause boilerplate code to overcome this we will use GSON (JSON Parsing Library from google) .

GSON Library allows both way of parsing.

1. From JSON to Model/Data Class ( JSON > Model/Data )
2. Model/Data to JSON ( Model/Data > JSON )

Gradle

Add GSON dependency to app level build.gradle file

dependencies {
    ............
 ............
    implementation 'com.google.code.gson:gson:2.8.5'
}

1.a  Simple JSON

In this tutorial we are reading file from assets folder of android

private fun readFromAssets(fileName: String): String {

        val bufferReader = application.assets.open(fileName).bufferedReader()
        return bufferReader.use {
            it.readText()
        }
    }

file : app/src/main/assets/sample.json

{
  "name": "John",
  "age": 29
}

Model /Data Class

file : Model.kt

package com.tutorialsbuzz.androifromgson

import com.google.gson.annotations.SerializedName

data class Model(
    @SerializedName("name") val name: String,
    @SerializedName("age") val age: Int
) {}

Parsing

 private fun fromJSimpleSONToModel(): Unit {
        val response = readFromAssets("sample.json")

        val gson = Gson()
        val model: Model = gson.fromJson(response, Model::class.java)

        Log.d("fromJSimpleSONToModel: ", "${model.name},${model.age}")
    }

Log-cat :

 com.tutorialsbuzz.androifromgson D/fromJSimpleSONToModel:: John,29

1.b ArrayOfJSONObject

file : app/src/main/assets/country.json

[
  {
    "name": "India",
    "capital": "Delhi"
  },
  {
    "name": "United States of America",
    "capital": "Washington D C"
  },
  {
    "name": "United Kingdom",
    "capital": "London"
  },
  {
    "name": "Australia",
    "capital": "Canbera"
  },
  {
    "name": "France",
    "capital": "Paris"
  },
  {
    "name": "Germany",
    "capital": "Berlin"
  },
  {
    "name": "Russia",
    "capital": "Moscow"
  },
  {
    "name": "Brazil",
    "capital": "Brasilia"
  },
  {
    "name": "Ukraine",
    "capital": "Kyiv"
  },
  {
    "name": "Kenya",
    "capital": "Nairobi"
  },
  {
    "name": "Switzerland",
    "capital": "Bern"
  },
  {
    "name": "Sweden",
    "capital": "Stockholm"
  },
  {
    "name": "New Zealand",
    "capital": "Wellington"
  }
]

Model/Data Class

file : Country.kt

package com.tutorialsbuzz.androifromgson

import com.google.gson.annotations.SerializedName

data class Country(
    @SerializedName("name") val name: String,
    @SerializedName("capital") val capital: String
) {}

Parsing

 private fun fromArrayOfJSONToModel(): Unit {

        val response = readFromAssets("country.json");

        val gson = Gson()
        val countryList: List<Country> = gson.fromJson(response, Array<Country>::class.java).toList()

        for (country: Country in countryList) {
            Log.d("fromArrayOfJSONToModel", "${country.name} , ${country.capital} \n")
        }
    }

Log-cat:

 com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: India , Delhi
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: United States of America , Washington D C
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: United Kingdom , London
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: Australia , Canbera
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: France , Paris
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: Germany , Berlin
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: Russia , Moscow
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: Brazil , Brasilia
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: Ukraine , Kyiv
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: Kenya , Nairobi
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: Switzerland , Bern
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: Sweden , Stockholm
com.tutorialsbuzz.androifromgson D/fromArrayOfJSONToModel: New Zealand , Wellington

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