RichJsPath.scala

package controllers

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

object RichJs {
  implicit class RichJsPath(js: JsPath) extends JsPath {
    // Read T element or try to convert from String
    def readStringified[T](toT: String => T)(implicit r: Reads[T], rS: Reads[String]): Reads[T] =
      Reads.at[T](js)(r) orElse Reads.at[String](js)(rS).map(toT(_)) // There is certainly a way to use automatic conversion...
    // Read Int and fallback to String conversion
    def readStringifiedInt: Reads[Int] = readStringified[Int](_.toInt)
  }
}

case class Example(name: String, number: Int)

object Example {
  import RichJs._
  implicit val formater = (
    (__ \ 'name).format[String] and
    (__ \ 'number).format((__).readStringifiedInt)
  )(Example.apply _, unlift(Example.unapply _))
}
object Application extends Controller {

  def index = Action {
    val json1 = Json.obj("name" -> "Julien", "number" -> 1000).as[Example]
    val json2 = Json.obj("name" -> "Julien", "number" -> "1000").as[Example]
    Ok(Json.toJson(json2))
  }
}

Or this way https://gist.github.com/02dca6d1b77f0be6bf72/06bad5eeb1aa5218095f3a996f20b0413f42b5e9