Kotlin Data Class from Json using GSON

I have Java POJO class like this:

class Topic {
    @SerializedName("id")
    long id;
    @SerializedName("name")
    String name;
}

and I have a Kotlin data class Like this

 data class Topic(val id: Long, val name: String)

How to provide the json key to any variables of the kotlin data class like the @SerializedName annotation in java variables ?

Data class:

data class Topic(
  @SerializedName("id") val id: Long, 
  @SerializedName("name") val name: String, 
  @SerializedName("image") val image: String,
  @SerializedName("description") val description: String
)

to JSON:

val gson = Gson()
val json = gson.toJson(topic)

from JSON:

val json = getJson()
val topic = gson.fromJson(json, Topic::class.java)

Based on answer of Anton Golovin

Details

• Gson version: 2.8.5
• Android Studio 3.1.4
• Kotlin version: 1.2.60

Solution

> Create any class data and inherit JSONConvertable interface

interface JSONConvertable {
     fun toJSON(): String = Gson().toJson(this)
}

inline fun <reified T: JSONConvertable> String.toObject(): T = Gson().fromJson(this, T::class.java)

Usage

Data class

data class User(
    @SerializedName("id") val id: Int,
    @SerializedName("email") val email: String,
    @SerializedName("authentication_token") val authenticationToken: String) : JSONConvertable

From JSON

val json = "..."
val object = json.toObject<User>()

To JSON

val json = object.toJSON()

You can use similar in Kotlin class

class InventoryMoveRequest {
    @SerializedName("userEntryStartDate")
    @Expose
    var userEntryStartDate: String? = null
    @SerializedName("userEntryEndDate")
    @Expose
    var userEntryEndDate: String? = null
    @SerializedName("location")
    @Expose
    var location: Location? = null
    @SerializedName("containers")
    @Expose
    var containers: Containers? = null
}

And also for nested class you can use same like if there is nested object. Just provide Serialize name for the Class.

@Entity(tableName = "location")
class Location {

    @SerializedName("rows")
    var rows: List<Row>? = null
    @SerializedName("totalRows")
    var totalRows: Long? = null

}

so if get response from the server each key will map with JOSN.

Alos, convert List to JSON:

val gson = Gson()
val json = gson.toJson(topic)

ndroid convert from JSON to Object:

val json = getJson()
val topic = gson.fromJson(json, Topic::class.java)