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

Question

我具有如JSON输入文件：

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

每个对象的某些字段丢失，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代码：

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

我得到下面的模式作为输出：

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

程序编译，但在运行时，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

• 如何解决这个异常，并遍历即使某些字段null或丢失的RDD匹配和创建对象？
• 为什么模式，即使我明确地定义了在某些字段上不可为空并且为空也是可以为空的？

UPDATE

我只是用一种变通方法上dataRdd以避免该问题：

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) 
    } 
} 

，并以这种方式改变MyCaseClass：

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

Answer 1

问题是与input.json。它应该是这样的：

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

有了这个input.json您的代码工作正常。