如何在数据集中使用java.time.LocalDate(使用java.lang.UnsupportedOperationException失败:找不到编码器)？

Question

• Spark 2.1.1
• 斯卡拉2.11.8
• Java 8
• Linux Ubuntu 16.04 LTS

我想将我的RDD转换为数据集.对于这一点,我用的implicits方法toDS()是给我下面的错误:

Exception in thread "main" java.lang.UnsupportedOperationException: No Encoder found for java.time.LocalDate
- field (class: "java.time.LocalDate", name: "date")
- root class: "observatory.TemperatureRow"
    at org.apache.spark.sql.catalyst.ScalaReflection$.org$apache$spark$sql$catalyst$ScalaReflection$$serializerFor(ScalaReflection.scala:602)
    at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$9.apply(ScalaReflection.scala:596)
    at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$9.apply(ScalaReflection.scala:587)
    at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
    at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
    at scala.collection.immutable.List.foreach(List.scala:381)
    at scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:241)
    at scala.collection.immutable.List.flatMap(List.scala:344)

在我的情况下,我必须使用类型java.time.LocalDate,我不能使用java.sql.data.我已经读过我需要将informe Spark变换为Java类型转换为Sql类型,我这个方向,我构建了下面的2个implicits函数:

implicit def toSerialized(t: TemperatureRow): EncodedTemperatureRow = EncodedTemperatureRow(t.date.toString, t.location, t.temperature)
implicit def fromSerialized(t: EncodedTemperatureRow): TemperatureRow = TemperatureRow(LocalDate.parse(t.date), t.location, t.temperature)

---

下面,我的应用程序的一些代码:

case class Location(lat: Double, lon: Double)

case class TemperatureRow(
                             date: LocalDate,
                             location: Location,
                             temperature: Double
                         )

case class EncodedTemperatureRow(
                             date: String,
                             location: Location,
                             temperature: Double

val s = Seq[TemperatureRow](
                    TemperatureRow(LocalDate.parse("2017-01-01"), Location(1.4,5.1), 4.9),
                    TemperatureRow(LocalDate.parse("2014-04-05"), Location(1.5,2.5), 5.5)
                )

import spark.implicits._
val temps: RDD[TemperatureRow] = sc.parallelize(s)
val tempsDS = temps.toDS

我不知道为什么Spark搜索编码器java.time.LocalDate,我提供了隐含的转换TemperatureRow和EncodedTemperatureRow...

Answer 1

java.time.LocalDate不支持Spark 2.2(我一直试图Encoder为该类型编写一段时间而且失败了).

您必须转换java.time.LocalDate为其他一些受支持的类型,java.sql.Timestamp或者java.sql.Date是受支持的候选者.