如何在Scala中使用GSON将RDD [String，String]转换为JSON

Question

我正在使用GSON转换RDD[String, String]，其中值（第二个字符串）可以是包含Maps和Lists的案例类。当我使用Gson.toJson时，它会像这样给空jsons：

 {"itemIds":{},"itemsNames":{}}

但我想：

{"itemIds":{"ABC" : 3,"123" : 33 },"itemsNames":{"ABC" : 3, "A" : 4}}

我试过GSON：

  val gson: Gson = new GsonBuilder().serializeNulls().create()
  def toJson(value: Any): String = {
     gson.toJson(value)
  }

 def getPersonRDD(result: DataFrame): RDD[(String, String)] = {

    val finalValue = result.rdd.map({
      r =>
        val customerId = r.getAs[String](CUSTOMER_ID)
        val itemId = r.getAs[Map[String, Int]](ITEM_ID)
        val itemName = r.getAs[Map[String, Int]](ITEM_NAME)


        val person = Person(itemId, itemName)

        val jsonString = toJson(person)

        (customerId, jsonString)

    })

    return finalValue
  }

  case class Person(itemId: Map[String, Int], itemNames: Map[String, Int]) extends Serializable

这给了我：

{"itemIds":{},"itemsNames":{}}

尝试了playJson，但收到了错误：

   trait JsonParser {
  def toJsonString(scenario: Person): String
}

     @SerialVersionUID(114L)
        class JsonParserImpl() extends JsonParser with Serializable {


          implicit val implicitPersonsWrites = new Writes[Person] {
            def writes(person: Person): JsValue = {
              Json.obj(
                "itemId" -> person.itemId,
                "itemNames" -> person.itemNames
              )
            }
          }

          def toJsonString(testDocument: Person): String = Json.toJson(testDocument).toString

        }

      def getPersonRDD(result: DataFrame): RDD[(String, String)] = {

            val jsonParserImpl = new JsonParserImpl
            val finalValue = result.rdd.map({
              r =>
                val customerId = r.getAs[String](CUSTOMER_ID)
                val itemId = r.getAs[Map[String, Int]](ITEM_ID)
                val itemName = r.getAs[Map[String, Int]](ITEM_NAME)


                val person = Person(itemId, itemName)

                val jsonString = jsonParserImpl.toJsonString(person)

                (customerId, jsonString)

            })

            return finalValue
          }

这给了我：

org.apache.spark.SparkException: Task not serializable
    [junit] java.lang.RuntimeException: org.apache.spark.SparkException: Task not serializable
    [junit]     at 
[

有人能告诉我这里做错了什么吗？我是scala / spark的新手。请告诉我如何实现这一目标。