为Play 2.1.1实现写入

Question

我是Play(和Scala)的新手.我正在尝试编写一个调用一些Java代码的简单Play应用程序.

我想将a转换scala.collection.mutable.Map[String,Array[String]]为JSON字符串.但这显然不起作用.

基于此,我假设我要实现写入.我当前的代码(显然不正确)如下所示:

implicit val myWrites = new Writes[scala.collection.mutable.Map[String,Array[String]]] {

def writes(res: scala.collection.mutable.Map[String,Array[String]]) = {

  val x  = res.foreach { kv => Json.obj(
      kv._1 -> ( kv._2.reduceLeft(_ + "," + _).mkString)

    ) }

    Json.toJson(x)

  }


}

任何有助于我取得进步的指针都将受到赞赏.

Answer 1

您不必编写任何Writes实现.您需要做的就是将可变映射转换为不可变映射,只需调用toMap方法即可:

scala> import play.api.libs.json._
import play.api.libs.json._

scala> import scala.collection.mutable
import scala.collection.mutable

scala> val im = Map("foo" -> Array("bar", "baz"))
im: scala.collection.immutable.Map[String,Array[String]] = Map(foo -> Array(bar, baz))

scala> Json.stringify(Json.toJson(im))
res8: String = {"foo":["bar","baz"]}

scala> val mm = mutable.Map("foo" -> Array("bar", "baz"))
mm: scala.collection.mutable.Map[String,Array[String]] = Map(foo -> Array(bar, baz))

scala> Json.stringify(Json.toJson(mm))
<console>:20: error: No Json deserializer found for type scala.collection.mutable.Map[String,Array[String]]. Try to implement an implicit Writes or Format for this type.
              Json.stringify(Json.toJson(mm))
                                        ^

scala> Json.stringify(Json.toJson(mm.toMap))
res10: String = {"foo":["bar","baz"]}