Pretty Printing JSON data in Kotlin

This post will discuss how to pretty print Json data in Kotlin.

1. Using GSON Library

To pretty-print a Json output with the Gson library, you can configure it for pretty-printing using the setPrettyPrinting() function. This is demonstrated below:

import com.google.gson.GsonBuilder

class Company(

var name: String,

var employees: Int,

var offices: List<String>

)

fun main() {

val jsonString = "{\"name\":\"Microsoft\",\"employees\":180000," +

"\"offices\":[\"Washington\",\"Virginia\",\"India\"]}"

val gson = GsonBuilder().setPrettyPrinting().create()

val company = gson.fromJson(jsonString, Company::class.java)

val prettyJsonString = gson.toJson(company)

println(prettyJsonString)

}

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Output:

{ "name": "Google", "employees": 180000, "offices": [ "Washington", "Virginia", "India" ] }

The fromJson function deserializes the specified Json into an object of the specified class. If the class information is not available, you can use JsonParser to parse Json into a parse tree of Json elements with either the parse() or parseString() function.

import com.google.gson.GsonBuilder

import com.google.gson.JsonParser

fun main() {

val jsonString = "{\"name\":\"Google\",\"employees\":180000," +

"\"offices\":[\"Washington\",\"Virginia\",\"India\"]}"

val jsonParser = JsonParser()

val jsonElement = jsonParser.parse(jsonString)

val gson = GsonBuilder().setPrettyPrinting().create()

val prettyJsonString = gson.toJson(jsonElement)

println(prettyJsonString)

}

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Output:

{ "name": "Google", "employees": 180000, "offices": [ "Washington", "Virginia", "India" ] }

2. Using Jackson Library

If you prefer the Jackson library, use the writerWithDefaultPrettyPrinter() function to output Json using the pretty printer for indentation. Here’s how the code would look like:

import com.fasterxml.jackson.databind.ObjectMapper

fun main() {

val jsonString = "{\"name\":\"Google\",\"employees\":180000," +

"\"offices\":[\"Washington\",\"Virginia\",\"India\"]}"

val mapper = ObjectMapper()

val prettyJsonString = mapper.writerWithDefaultPrettyPrinter()

.writeValueAsString(jsonString)

println(prettyJsonString)

}

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Output:

{ "employees": 180000, "name": "Google", "offices": [ "Washington", "Virginia", "India" ] }

3. Using Json for Java Library

The Json for Java library provides the JsonObject.toString() function to output a pretty-printed representation of the Json object. It can be used as follows:

import org.json.JsonException

import org.json.JsonObject

fun main() {

val jsonString = "{\"name\":\"Google\",\"employees\":180000," +

"\"offices\":[\"Washington\",\"Virginia\",\"India\"]}"

try {

val json = JsonObject(jsonString)

val prettyJsonString = json.toString(4)

println(prettyJsonString)

} catch (e: JsonException) {

e.printStackTrace()

}

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Output:

{ "employees": 180000, "name": "Google", "offices": [ "Washington", "Virginia", "India" ] }

That’s all about pretty printing Json data in Kotlin.