An introduction to json mapping in play! covering reads, writes and path search

1. Json mapping in pLAY!
Fabian Gutierrez

2. Mandatory verbose java example
Jonathan
@JsonInclude(JsonInclude.Include.NON_NULL)
@Generated("org.jsonschema2pojo")
@JsonPropertyOrder({ "name", "age" })
public class Actor {
@JsonProperty("nombre") private String name;
@JsonProperty("age") private Integer age;
…
}

4. Seriously
● Building JsValues
● Reads
● Writes
● Paths

5. Play’s json mapper

6. Building a JsValue
Types
● JsString
● JsNumber
● JsBoolean
● JsObject
● JsArray
● JsNull
Json.parse("""
|{
| "name" : "Jennifer",
| "Age": 26
|}
""".stripMargin
)

7. The Reader

8. Reading Json
case class Actor(name: String, age: Int)
object Actor {
// or default values
implicit val actorReads = Json.reads[Actor]
// functional syntax
implicit val actorReads: Reads[Actor] = (
(JsPath "nombre").read[String] and
(JsPath "age").read[Int]
)(Actor.apply _)
}

9. The (ghost) writer

10. Writing Json
object Actor {
//default values
implicit val actorWrites = Json.writes[Actor]
//or total control
implicit val actorWrites = new Writes[Actor] {
def writes(actor: Actor) = Json.obj(
"name" -> actor.name,
"age" -> actor.age
)
}
//or functional syntax
implicit val actorWrites: Writes[Actor] = (
(JsPath "name").write[String] and
(JsPath "age").write[Int]
)(unlift(Actor.unapply))
}

12. Paths
// direct parsing
val jsPerson: JsObject = ...
(jsPerson "name").as[String]
(jsPerson "age").as[Int]
// as optionals
val jsPersonList: JsObject = ...
(jsPersonList "name").asOpt[List[String]]

13. https://github.com/fagossa/xke_play_json