parse Json to Generic Java Map in Scala, similar to Jackson.

Json2JavaMap.scala

  import com.google.gson.Gson
  import java.util.{Map => JMap, LinkedHashMap}

  type GenericDecoder = String => JMap[String, Object]

  val decoder: GenericDecoder = {
    // Gson instances are apparently thread-safe, so curry...
    val gson: Gson = new Gson()
    // LinkedHashMap preserves ordering. use HashMap if not required.
    x => gson.fromJson(x, (new LinkedHashMap[String, Object]()).getClass)
  }

  val json = """
    |{
    | "hello": "world",
    | "foods": ["macaroni", "broccoli", {"foo": "bar"}]
    |}
    |""".stripMargin

  decode(json)  // woohoo!
  
  // validate roundtrip with Play Json
  import play.api.libs.json._
  Json.stringify(Json.parse(test)) == gson.toJson(decoder(test)) // true