build.sbt

libraryDependencies += "com.typesafe.play" %% "play-json" % "2.3.7"

resolvers += "typesafe" at "http://typesafe.artifactoryonline.com/typesafe/releases"

scalaVersion := "2.11.4"

EitherReadsExample.scala

import play.api.libs.json._

// https://groups.google.com/d/topic/play-framework/anYvYB-8GYs/discussion
object EitherReadsExample {

  implicit def eitherReads[A, B](implicit A: Reads[A], B: Reads[B]): Reads[Either[A, B]] =
    Reads[Either[A, B]] { json =>
      A.reads(json) match {
        case JsSuccess(value, path) => JsSuccess(Left(value), path)
        case JsError(e1) => B.reads(json) match {
          case JsSuccess(value, path) => JsSuccess(Right(value), path)
          case JsError(e2) => JsError(JsError.merge(e1, e2))
        }
      }
    }

  val json = Json.parse("""[
    {
      "id":2158488,
      "name":"LIVE",
      "screen_name":"live",
      "is_closed":0,
      "type":"page",
      "photo_50":"https://pp.vk.me/c623416/v623416604/10e29/AUwb4GWpbD4.jpg",
      "photo_100":"https://pp.vk.me/c623416/v623416604/10e28/DNSjabzHo70.jpg",
      "photo_200":"https://pp.vk.me/c623416/v623416604/10e26/UAWL2PWZ_wM.jpg"
    },
    {
      "id":11982368,
      "name":"Forbes",
      "screen_name":"forbes",
      "is_closed":0,
      "type":"page",
      "photo_50":"https://pp.vk.me/c621326/v621326364/46b3/PE8CH3wuGSU.jpg",
      "photo_100":"https://pp.vk.me/c621326/v621326364/46b2/_K_Pn8ayf08.jpg",
      "photo_200":"https://pp.vk.me/c621326/v621326364/46b1/U58-5jSTiHI.jpg"
    },
    {
      "type":"profile",
      "id":123456,
      "first_name":"John",
      "last_name":"Doe"
    }
  ]""")

  case class Page(id: Int, name: String, screen_name: String, is_closed: Int, photo_50: String, photo_100: String, photo_200: String)

  implicit val pageReads = Json.reads[Page]

  case class Profile(id: Int, first_name: String, last_name: String)

  implicit val profileReads = Json.reads[Profile]

  def main(args: Array[String]): Unit = {
    println(json.validate[Seq[Either[Profile, Page]]])
  }
}

@xuwei-k see my fork for a full Format implementation: https://gist.github.com/graingert/7b1c9d20fb5f4cb081dd5a640ca335f4#file-jseither-scala

if you have ambiguous Either's then it will default to Left:

case class Foo(
foo: Either[Float, Int]
}
Foo(Right(1)) // BEWARE: round trips to Foo(Left(1.0))