Parse a JSON String in Kotlin

This post will discuss how to parse a JSON String in Kotlin.

Kotlin doesn’t provide any support for converting a JSON string to an object. This post provides an overview of some of the available alternatives to accomplish this.

1. Using Gson

Google’s Gson library can be used to convert a JSON string to an equivalent Java object. You can use the Gson#fromJson() function to facilitate this conversion. The following code demonstrates this:

import com.google.gson.Gson

class Person {

var name: String? = null

var age: Int? = null

var student: Student? = null

override fun toString(): String {

return "Person(name=$name, age=$age, student=$student)"

}

class Student {

var studentId: String? = null

var subjects: List<String>? = null

override fun toString(): String {

return "Student(studentId=$studentId, subjects=$subjects)"

}

fun main() {

val jsonString = "{\"name\":\"Peter Parker\",\"age\":22," +

"\"student\":{\"studentId\":\"Jon_Snow_22\"," +

"\"subjects\":[\"Maths\",\"Science\"]}}"

println("JSON string is: $jsonString")

val person = Gson().fromJson(jsonString, Person::class.java)

println("Person object: $person")

}

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Output:
JSON string is: {"name":"Peter Parker","age":22,"student":{"studentId":"Jon_Snow_22","subjects":["Maths","Science"]}} Person object: Person(name=Peter Parker, age=22, student=Student(studentId=Jon_Snow_22, subjects=[Maths, Science]))

2. Using Jackson

If you prefer the Jackson library over Gson, you can use its ObjectMapper#readValue() function to convert the JSON string into the specified object. Here’s the sample code:

import org.codehaus.jackson.map.ObjectMapper

class Person {

var name: String? = null

var age: Int? = null

var student: Student? = null

override fun toString(): String {

return "Person(name=$name, age=$age, student=$student)"

}

class Student {

var studentId: String? = null

var subjects: List<String>? = null

override fun toString(): String {

return "Student(studentId=$studentId, subjects=$subjects)"

}

fun main() {

val jsonString = "{\"name\":\"Peter Parker\",\"age\":22," +

"\"student\":{\"studentId\":\"Jon_Snow_22\"," +

"\"subjects\":[\"Maths\",\"Science\"]}}"

println("JSON string is: $jsonString")

val person = ObjectMapper().readValue(jsonString, Person::class.java)

println("Person object: $person")

}

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That’s all about parsing a JSON String in Kotlin.

Parse a JSON String in Kotlin

1. Using Gson

2. Using Jackson

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