是什么导致了scala中的类型转换

Question

有一个hashMap parsedRecord，类型是scala.collection.immutable.HashMap，我获取类型的方式是：

logger.info(s"parsedRecord: ${parsedRecord}")
logger.info(s"parsedRecord type: ${parsedRecord.getClass}")

我们会得到另一个地图，这是一个 spark streaming 作业，记录来自 kafka 集群，代码如下：

val finalRecord = (record: Map[String, Any]) => {

    record.get("operation").get.toString match {
      case "view" => parsedRecord + ("view" -> 1, "impression" -> 0, "click" -> 0)
      case "impression" => parsedRecord + ("view" -> 0, "impression" -> 1, "click" -> 0)
      case "click" => parsedRecord + ("view" -> 0, "impression" -> 0, "click" -> 1)
    }
  }

recordList += finalRecord.asInstanceOf[scala.collection.immutable.HashMap[String, Any]]

这些代码我会得到类型为map的finalRecord，但是有一个例外是这样的：

Caused by: java.lang.ClassCastException: com.shopee.mall.data.ParseOperation$$anonfun cannot be cast to scala.collection.immutable.HashMap
at com.shopee.mall.data.ParseOperation$.parseRecord(ParseOperation.scala:88)
at com.shopee.mall.data.ParseOperation$$anonfun.apply(ParseOperation.scala:14)
at com.shopee.mall.data.ParseOperation$$anonfun.apply(ParseOperation.scala:12)
at com.shopee.mall.data.ParseOperation$$anonfun.apply(ParseOperation.scala:105)
at com.shopee.mall.data.ParseOperation$$anonfun.apply(ParseOperation.scala:102)
at com.shopee.mall.data.OfficialMallTracker$$anonfun.apply(OfficialMallTracker.scala:70)
at com.shopee.mall.data.OfficialMallTracker$$anonfun.apply(OfficialMallTracker.scala:70)
at scala.collection.Iterator$$anon.nextCur(Iterator.scala:434)
at scala.collection.Iterator$$anon.hasNext(Iterator.scala:440)
at scala.collection.Iterator$class.foreach(Iterator.scala:893)
at scala.collection.AbstractIterator.foreach(Iterator.scala:1336)
at scala.collection.generic.Growable$class.$plus$plus$eq(Growable.scala:59)
at scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:104)
at scala.collection.mutable.ArrayBuffer.$plus$plus$eq(ArrayBuffer.scala:48)
at scala.collection.TraversableOnce$class.to(TraversableOnce.scala:310)
at scala.collection.AbstractIterator.to(Iterator.scala:1336)
at scala.collection.TraversableOnce$class.toBuffer(TraversableOnce.scala:302)
at scala.collection.AbstractIterator.toBuffer(Iterator.scala:1336)
at scala.collection.TraversableOnce$class.toArray(TraversableOnce.scala:289)
at scala.collection.AbstractIterator.toArray(Iterator.scala:1336)
at org.apache.spark.rdd.RDD$$anonfun$collect$$anonfun.apply(RDD.scala:936)
at org.apache.spark.rdd.RDD$$anonfun$collect$$anonfun.apply(RDD.scala:936)
at org.apache.spark.SparkContext$$anonfun$runJob.apply(SparkContext.scala:1951)
at org.apache.spark.SparkContext$$anonfun$runJob.apply(SparkContext.scala:1951)
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87)
at org.apache.spark.scheduler.Task.run(Task.scala:99)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:322)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

Answer 1

these code I would get the finalRecord whose type is map

不，您将 finalRecord 定义为接受和 returns 映射的函数。要获取地图，您需要将其应用于某些地图，例如

recordList += finalRecord(parsedRecord)

除非必要，否则您应该尽量避免asInstanceOf。例如。如果您需要它，因为 recordList 被定义为包含 HashMap，请考虑将其更改为包含 Map。

是什么导致了scala中的类型转换

what caused the type convertion in scala

scala

spark-streaming