Kotlin convert json array to model list using GSON

Question

I am not able to convert a JSON Array into a GroupModel array. Below is the JSON I used:

[{
  "description":"My expense to others",
  "items":["aaa","bbb"],
  "name":"My Expense"
 },
 {
  "description":"My expense to others","
  items":["aaa","bbb"],
  "name":"My Expense"
 }]

and the GroupModel class is:

class GroupModel {
    var name: String? = null
    var description: String? = null
    var items: MutableList<String>? = null

    constructor(name: String, description: String, items: MutableList<String>) {
        this.name = name
        this.description = description
        this.items = items
    }
}

and trying the following code results in an Exception:

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2 path $

The code:

var model = gson.fromJson<Array<GroupModel>>(inputString, GroupModel::class.java)

BIS Tech · Accepted Answer · 2019-01-04 17:40:28Z

27

[{
  "description":"My expense to others",
  "items":["aaa","bbb"],
  "name":"My Expense"
 },
 {
  "description":"My expense to others","
  items":["aaa","bbb"],
  "name":"My Expense"
 }]

Kotlin Code

val gson = GsonBuilder().create()
val Model= gson.fromJson(body,Array<GroupModel>::class.java).toList()

Gradle

implementation 'com.google.code.gson:gson:2.8.5'

answered Jan 4, 2019 at 17:40

BIS Tech

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Comments

xarlymg89 · Accepted Answer · 2020-07-06 17:11:05Z

17

I have found a solution that is actually working on Android with Kotlin for parsing JSON arrays of a given class. The solution of @Aravindraj didn't really work for me.

val fileData = "your_json_string"
val gson = GsonBuilder().create()
val packagesArray = gson.fromJson(fileData , Array<YourClass>::class.java).toList()

So basically, you only need to provide a class (YourClass in the example) and the JSON string. GSON will figure out the rest.

The Gradle dependency is:

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

edited Jul 6, 2020 at 17:11

answered Oct 24, 2018 at 9:35

xarlymg89

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Comments

Jayson Minard · Accepted Answer · 2018-02-19 18:31:09Z

10

You need to use a TypeToken to capture the generic type of the array, and you need this to be the type that GSON sees as the target, instead of just GroupModel::class it is really a list of those. You can create a TypeToken and use it as follows:

Type groupListType = new TypeToken<ArrayList<GroupModel>>() {}.getType();
var model = gson.fromJson(inputString, groupListType);

edited Feb 19, 2018 at 18:31

Jayson Minard

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answered Feb 19, 2018 at 12:27

Aravindraj

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2 Comments

Himanshu Mori Over a year ago

what about this stackoverflow.com/questions/45603236/… ? ?

oiyio Over a year ago

This should not be the accepted answer. This answer does not work. The below 2 answer works correctly.

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