scala.MatchError：[ABC空，CDE，3]（的類org.apache.spark.sql.catalyst.expressions.GenericRowWithSchema）在火花JSON與丟失的字段

Question

我具有如JSON輸入文件：

{"a": "abc", "b": "bcd", "d": 3}, 
{"a": "ezx", "b": "hdg", "c": "ssa"}, 
... 

每個對象的某些字段丟失，而不是放置null值。使用Scala的

在Apache中星火：

import SparkCommons.sparkSession.implicits._ 

private val inputJsonPath: String = "resources/input/input.json" 

private val schema = StructType(Array(
    StructField("a", StringType, nullable = false), 
    StructField("b", StringType, nullable = false), 
    StructField("c", StringType, nullable = true), 
    StructField("d", DoubleType, nullable = true) 
)) 

private val inputDF: DataFrame = SparkCommons.sparkSession 
    .read 
    .schema(schema) 
    .json(inputJsonPath) 
    .cache() 

inputDF.printSchema() 

val dataRdd = inputDF.rdd 
.map { 
    case Row(a: String, b: String, c: String, d: Double) => 
    MyCaseClass(a, b, c, d) 
} 

val dataMap = dataRdd.collectAsMap() 

的MyCaseClass代碼：

case class MyCaseClass(
       a: String, 
       b: String, 
       c: String = null, 
       d: Double = Predef.Double2double(null) 
) 

我得到下面的模式作爲輸出：

root 
|-- a: string (nullable = true) 
|-- b: string (nullable = true) 
|-- c: string (nullable = true) 
|-- d: double (nullable = true) 

程序編譯，但在運行時，一旦星火正在做的工作，我得到以下例外：

[error] - org.apache.spark.executor.Executor - Exception in task 3.0 in stage 4.0 (TID 21) 
scala.MatchError: [abc,bcd,null,3] (of class org.apache.spark.sql.catalyst.expressions.GenericRowWithSchema) 
at com.matteoguarnerio.spark.SparkOperations$$anonfun$1.apply(SparkOperations.scala:62) ~[classes/:na] 
at com.matteoguarnerio.spark.SparkOperations$$anonfun$1.apply(SparkOperations.scala:62) ~[classes/:na] 
at scala.collection.Iterator$$anon$11.next(Iterator.scala:410) ~[scala-library-2.11.11.jar:na] 
at scala.collection.Iterator$$anon$11.next(Iterator.scala:410) ~[scala-library-2.11.11.jar:na] 
at scala.collection.Iterator$$anon$11.next(Iterator.scala:410) ~[scala-library-2.11.11.jar:na] 
at org.apache.spark.util.random.SamplingUtils$.reservoirSampleAndCount(SamplingUtils.scala:42) ~[spark-core_2.11-2.0.2.jar:2.0.2] 
at org.apache.spark.RangePartitioner$$anonfun$9.apply(Partitioner.scala:261) ~[spark-core_2.11-2.0.2.jar:2.0.2] 
at org.apache.spark.RangePartitioner$$anonfun$9.apply(Partitioner.scala:259) ~[spark-core_2.11-2.0.2.jar:2.0.2] 
at org.apache.spark.rdd.RDD$$anonfun$mapPartitionsWithIndex$1$$anonfun$apply$25.apply(RDD.scala:820) ~[spark-core_2.11-2.0.2.jar:2.0.2] 
at org.apache.spark.rdd.RDD$$anonfun$mapPartitionsWithIndex$1$$anonfun$apply$25.apply(RDD.scala:820) ~[spark-core_2.11-2.0.2.jar:2.0.2] 
at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38) ~[spark-core_2.11-2.0.2.jar:2.0.2] 
at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:319) ~[spark-core_2.11-2.0.2.jar:2.0.2] 
at org.apache.spark.rdd.RDD.iterator(RDD.scala:283) ~[spark-core_2.11-2.0.2.jar:2.0.2] 
at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:70) ~[spark-core_2.11-2.0.2.jar:2.0.2] 
at org.apache.spark.scheduler.Task.run(Task.scala:86) ~[spark-core_2.11-2.0.2.jar:2.0.2] 
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:274) ~[spark-core_2.11-2.0.2.jar:2.0.2] 
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_144] 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_144] 
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_144] 

星火版本：2.0.2

斯卡拉版本：2.11.11

• 如何解決這個異常，並遍歷即使某些字段null或丟失的RDD匹配和創建對象？
• 爲什麼模式，即使我明確地定義了在某些字段上不可爲空並且爲空也是可以爲空的？

UPDATE

我只是用一種變通方法上dataRdd以避免該問題：

private val dataRdd = inputDF.rdd 
.map { 
    case r: GenericRowWithSchema => { 
     val a = r.getAs("a").asInstanceOf[String] 
     val b = r.getAs("b").asInstanceOf[String] 

     var c: Option[String] = None 
     var d: Option[Double] = None 

     try { 
     c = if (r.isNullAt(r.fieldIndex("c"))) None: Option[String] else Some(r.getAs("c").asInstanceOf[String]) 
     d = if (r.isNullAt(r.fieldIndex("d"))) None: Option[Double] else Some(r.getAs("d").asInstanceOf[Double]) 
     } catch { 
     case _: Throwable => None 
     } 

     MyCaseClass(a, b, c, d) 
    } 
} 

，並以這種方式改變MyCaseClass：

case class MyCaseClass(
       a: String, 
       b: String, 
       c: Option[String], 
       d: Option[Double] 
) 

Answer 1

問題是與input.json。它應該是這樣的：

{"a": "abc", "b": "bcd", "d": 3}, 
{"a": "ezx", "b": "hdg", "c": "ssa"}, 
... 

有了這個input.json您的代碼工作正常。