Scala Cookbook

15.1. Creating a JSON String from a Scala Object

Problem

You’re working outside of a specific framework, and want to create a JSON string from a Scala object.

Solution

If you’re using the Play Framework, you can use its library to work with JSON, as shown in Recipes 15.13 and 15.14, but if you’re using JSON outside of Play, you can use the best libraries that are available for Scala and Java:

• Lift-JSON

• The Google Gson library (Java)

• Json4s

• spray-json

This recipe demonstrates the Lift-JSON and Gson libraries. (Json4s is a port of Lift-JSON, so it shares the same API.)

Lift-JSON solution

To demonstrate the Lift-JSON library, create an empty SBT test project. With Scala 2.10 and SBT 0.12.x, configure your build.sbt file as follows:

name := "Basic Lift-JSON Demo"

version := "1.0"

scalaVersion := "2.10.0"

libraryDependencies += "net.liftweb" %% "lift-json" % "2.5+"

Next, in the root directory of your project, create a file named LiftJsonTest.scala:

import scala.collection.mutable._
import net.liftweb.json._
import net.liftweb.json.Serialization.write

case class Person(name: String, address: Address)
case class Address(city: String, state: String)

object LiftJsonTest extends App {

  val p = Person("Alvin Alexander", Address("Talkeetna", "AK"))

  // create a JSON string from the Person, then print it
  implicit val formats = DefaultFormats
  val jsonString = write(p)
  println(jsonString)

}

This code creates a JSON string from the Person instance, and prints it. When you run the project with the sbt run command, ...