json4s parsing StructType

[cwang9208]

json4s version

All versions

scala version

2.12

jdk version

java 8

I'm trying to leverage json4s for parsing the StructType from Spark.

scala> import org.apache.spark.sql.types._

scala> case class Person(name: StructType)
defined class Person

scala> import org.json4s._
import org.json4s._

scala> import org.json4s.jackson.JsonMethods._
import org.json4s.jackson.JsonMethods._

scala> implicit val formats: Formats = DefaultFormats

scala> val json = parse("""  {"name": []} """)

scala> json.extract[Person]

org.json4s.package$MappingException: unknown error
  at org.json4s.Extraction$.extract(Extraction.scala:43)
  at org.json4s.ExtractableJsonAstNode.extract(ExtractableJsonAstNode.scala:21)
  ... 55 elided
Caused by: java.util.NoSuchElementException: head of empty list
  at scala.collection.immutable.Nil$.head(List.scala:431)
  at scala.collection.immutable.Nil$.head(List.scala:428)
  at org.json4s.Extraction$CollectionBuilder.<init>(Extraction.scala:407)
  at org.json4s.Extraction$$anonfun$extract$5.apply(Extraction.scala:382)
  at org.json4s.Extraction$$anonfun$extract$5.apply(Extraction.scala:382)
  at org.json4s.Extraction$.customOrElse(Extraction.scala:606)
  at org.json4s.Extraction$.extract(Extraction.scala:382)
  at org.json4s.Extraction$ClassInstanceBuilder.org$json4s$Extraction$ClassInstanceBuilder$$buildCtorArg(Extraction.scala:514)
  at org.json4s.Extraction$ClassInstanceBuilder$$anonfun$15.apply(Extraction.scala:546)
  at org.json4s.Extraction$ClassInstanceBuilder$$anonfun$15.apply(Extraction.scala:546)
  at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
  at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
  at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
  at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48)
  at scala.collection.TraversableLike$class.map(TraversableLike.scala:234)
  at scala.collection.AbstractTraversable.map(Traversable.scala:104)
  at org.json4s.Extraction$ClassInstanceBuilder.instantiate(Extraction.scala:546)
  at org.json4s.Extraction$ClassInstanceBuilder.result(Extraction.scala:597)
  at org.json4s.Extraction$$anonfun$extract$6.apply(Extraction.scala:400)
  at org.json4s.Extraction$$anonfun$extract$6.apply(Extraction.scala:392)
  at org.json4s.Extraction$.customOrElse(Extraction.scala:606)
  at org.json4s.Extraction$.extract(Extraction.scala:392)
  at org.json4s.Extraction$.extract(Extraction.scala:39)
  ... 56 more

StructType in Spark is actually a Spark case class with an array as parameter:

case class StructType(fields: Array[StructField]) extends DataType with Seq[StructField]

I just passed an empty list in json, I think that should work. Can any one help me fix this problem?