Month: July 2017

This is something I’ve had to look up a few times, so I figured it’s time to write up something to ease the next time a bit.

First we need to include the Play JSON library itself to build.sbt

	name := """minimal-scala"""
	version := "1.0"
	scalaVersion := "2.11.7"
	libraryDependencies += "com.typesafe.play" %% "play-json" % "2.5.13"

view raw build.sbt hosted with by GitHub

Using case classes seems to be the most used method of holding data to be encoded in JSON. So the next step is to configure out case class InventoryItem for reading and writing (decoding / encoding) into JSON with a companion object.

	object InventoryItem {
	implicit val inventoryItemWrites: Writes[InventoryItem] = (
	(JsPath \ "name").write[String] and
	(JsPath \ "serialNumber").write[String] and
	(JsPath \ "value").write[Float]
	)(unlift(InventoryItem.unapply))
	implicit val inventoryItemReads: Reads[InventoryItem] = (
	(JsPath \ "name").read[String] and
	(JsPath \ "serialNumber").read[String] and
	(JsPath \ "value").read[Float]
	)(InventoryItem.apply _)
	}
	case class InventoryItem(name: String, serialNumber: String, value: Float) {}

view raw inventoryitem.scala hosted with by GitHub

I’m using an example where we write a list of InventoryItems into JSON. Play JSON knows how to handle Lists automatically so no configuration is needed for that.

	object WritingJson extends App {
	var inventory = List[InventoryItem]()
	inventory = inventory :+ InventoryItem("Name", "SR-001", 33.0)
	val json = Json.toJson(inventory)
	println(Json.stringify(json))
	}

view raw writingjson.scala hosted with by GitHub

List of IntentoryItems would like something like this in JSON.

	[
	{
	"name": "Item",
	"serialNumber": "asdsad",
	"value": 22
	},
	{
	"name": "Another Item",
	"serialNumber": "SRS-001",
	"value": 33
	}
	]

view raw result.json hosted with by GitHub

Reading JSON is from a string is a bit more involved than writing it.

	object ReadingJson extends App {
	var inventory: List[InventoryItem] = List()
	val itemJsonString = Source.fromFile("D:\\Path\\To\\My.json").mkString
	val json = Json.parse(itemJsonString)
	json.validate[List[InventoryItem]] match {
	case s: JsSuccess[List[InventoryItem]] => inventory = s.get
	case e: JsError => println("Oh dog, what done")
	}
	}

view raw readingjson.scala hosted with by GitHub