Parse Json Sequence without keys in playframework

Question

I am trying to parse a Json object that consists only of an top level array without a key.

import play.api.libs.json._
import play.api.libs.functional.syntax._

case class Name(first: String, last: String)
case class Names(names: Seq[Name])

implicit val NameF = Json.format[Name]

val s = """[{"first": "A", "last": "B"},{"first": "C", "last": "D"},{"first": "E", "last": "F"}]"""

implicit val NF: Reads[Names] = (
    JsPath.read[Seq[Name]]
)(Names.apply _)

<console>:34: error: overloaded method value read with alternatives:
  (t: Seq[Name])play.api.libs.json.Reads[Seq[Name]] <and>
  (implicit r: play.api.libs.json.Reads[Seq[Name]])play.api.libs.json.Reads[Seq[Name]]
 cannot be applied to (Seq[Name] => Names)
            JsPath.read[Seq[Name]]

Ido Tamir · Accepted Answer · 2014-09-16 15:08:45Z

3

One possiblity is by creating an implicit Reads function:

  def readNames: Reads[Names] = new Reads[Names] {
    def reads(json: JsValue) = {
      json.validate[Seq[Name]].map(succ => Names(succ))
    }
  }

  implicit val NamesFormat = readNames

answered Sep 16, 2014 at 15:08

Ido Tamir

3,1672 gold badges21 silver badges31 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Michael Zajac Over a year ago

It seems rather ham-fisted to wrap Seq within another container, though.

Ido Tamir Over a year ago

Its necessary because I have a method query[T](qs: String)(implicit r: Read[T]): NonEmptyList[String] \/ T . and in the method it calls a web service and the response is parsed: Json.parse(s).validate[T]

Michael Zajac · Accepted Answer · 2014-09-15 13:06:23Z

2

You don't need to specify Reads for Seq[Name] if you already have one defined for Name.

case class Name(first: String, last: String)

implicit val NameF = Json.format[Name]

val s = """[{"first": "A", "last": "B"},{"first": "C", "last": "D"},{"first": "E", "last": "F"}]"""

scala> Json.parse(s).validate[Seq[Name]]
res2: play.api.libs.json.JsResult[Seq[Name]] = JsSuccess(List(Name(A,B), Name(C,D), Name(E,F)),)

answered Sep 15, 2014 at 13:06

Michael Zajac

55.7k7 gold badges120 silver badges143 bronze badges

3 Comments

Ido Tamir Over a year ago

But I would like to write Json.parse(s).validate[Names]. Is this possible?

Michael Zajac Over a year ago

Not without a key like you have it. But why duplicate the code when the above method works perfectly fine?

Ido Tamir Over a year ago

Its possible and I actually need it to abstract over Reads[T]

Collectives™ on Stack Overflow

Parse Json Sequence without keys in playframework

2 Answers 2

2 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related