Scala Play: How to map JSON array structure to Case Class

Question

I'm completely new to Scala and Play and i stumbled upon the following the problem:

Given the following JSON structure:

[
  {
    "name": "Adam",
    "age": 19
  },
  {
    "name": "Berta",
    "age": 22
  },
...
]

I would like to map this JSON to a case classes like this:

case class User(name: String, age: Int)
case class Users(users: Seq[User])

or at least something like Seq[User].

I don't know how to traverse the JsPath because there is no key.

I tried to define an implicit read but either he cannot resolve the symbol "read" or he cannot found an implicit for user.

object User {
  implicit val reads: Reads[User] = Json.reads[User]
}
object Users {
  implicit val usersReads: Reads[Users] = (
    (JsPath).read[Seq[User]]
  )(Users.apply _)
}

How can I map my JSON to a working model?

olzhas · Accepted Answer · 2020-01-28 19:31:12Z

3

Something like this will work

import play.api.libs.json._

case class User(name: String, age: Int)
case class Users(users: Seq[User])

object User {
  implicit val reads = Json.reads[User]
}

object Users {
  implicit val reads: Reads[Users] = Reads {
      _.validate[Seq[User]].map(Users(_))
    }
}

answered Jan 28, 2020 at 19:31

olzhas

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3 Comments

Lotus Over a year ago

It works but my IntelliJ told my that no implicits could be found for Seq[User]..however could you shortly explain what the map part does? Thx!

jrook Over a year ago

You don't even need the second implicit object. Json.parse(s).as[Seq[User]] works just fine too.

olzhas Over a year ago

its just .map(users => Users(users))

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