This is mainly a note to self on how to build inheritance hierarchies (e.g. Animal -> [Cat / Dog] ) with Play-JSON.
| import play.api.libs.json._ | |
| sealed trait Animal { | |
| val `type`: String | |
| } | |
| case class Cat(name: String) extends Animal { | |
| override val `type`: String = "cat" | |
| } | |
| case class Dog(name: String) extends Animal { | |
| override val `type`: String = "dog" | |
| } | |
| trait AnimalJsonSupport | |
| extends de.heikoseeberger.akkahttpplayjson.PlayJsonSupport { | |
| implicit val catReads: Reads[Cat] = | |
| (JsPath \ "name").read[String].map(Cat(_)) | |
| implicit val dogReads: Reads[Dog] = | |
| (JsPath \ "name").read[String].map(Dog(_)) | |
| implicit val catWrites: Writes[Cat] = e => | |
| JsObject(Seq("type" –> JsString("cat"), "name" –> JsString(e.name))) | |
| implicit val dogWrites: Writes[Dog] = e => | |
| JsObject(Seq("type" –> JsString("dog"), "name" –> JsString(e.name))) | |
| implicit val animalReads: Reads[Animal] = Reads[Animal](jsValue => { | |
| (jsValue \ "type").toEither | |
| .map( | |
| v => | |
| v.as[String] match { | |
| case "cat" => catReads.map(_.asInstanceOf[Animal]).reads(jsValue) | |
| case "dog" => dogReads.map(_.asInstanceOf[Animal]).reads(jsValue) | |
| case t => | |
| JsError((JsPath \ "type"), "unkown animal type $t") | |
| .asInstanceOf[JsResult[Animal]] | |
| } | |
| ) | |
| .fold(v => JsError(JsPath, v).asInstanceOf[JsResult[Animal]], v => v) | |
| }) | |
| implicit val animalWrites: Writes[Animal] = Json.writes[Animal] | |
| } |
| import org.scalatest.matchers.should.Matchers | |
| import org.scalatest.wordspec.AnyWordSpec | |
| import play.api.libs.json.Json | |
| class AnimalJsonSupportSpec | |
| extends AnyWordSpec | |
| with Matchers | |
| with AnimalJsonSupport | |
| { | |
| val catJsonString = | |
| """ | |
| |{ | |
| |"type":"cat", | |
| |"name":"test" | |
| |} | |
| |""".stripMargin.replace("\n", "") | |
| val dummyRequestResponse = Cat("test") | |
| "The AnimalJsonSupport" when { | |
| "handling the Cat-Type" should { | |
| "correctly serialize the response" in { | |
| Json.toJson(dummyRequestResponse).toString() should ===(catJsonString) | |
| } | |
| "correctly deserialize the cat response" in { | |
| val parseResult = Json.fromJson[Animal](Json.parse(catJsonString)) | |
| parseResult.get should ===(dummyRequestResponse) | |
| } | |
| } | |
| "handling the Dog-Type" should { | |
| "correctly deserialize the dog response" in { | |
| val json = | |
| """ | |
| |{ | |
| |"type":"dog", | |
| |"name":"test2" | |
| |} | |
| |""".stripMargin.replace("\n", "") | |
| val parseResult = Json.fromJson[Animal](Json.parse(json)) | |
| parseResult.get should ===(Dog("test2")) | |
| } | |
| } | |
| "handling other types" should { | |
| "fail trying to deserialize a unknown type" in { | |
| val json = """ | |
| |{ | |
| |"type":"unknown", | |
| |"name":"test" | |
| |} | |
| |""".stripMargin.replace("\n", "") | |
| val result = Json.fromJson[Animal](Json.parse(json)) | |
| result.isError shouldBe(true) | |
| } | |
| } | |
| } | |
| } |
Documentation can be found here: