Scala Case Class serialization - scala

Question

I've been trying to binary serialize a composite case class object that kept throwing a weird exception. I don't really understand what is wrong with this example which throws the following exception. I used to get that exception for circular references which is not the case here. Some hints please?
java.lang.ClassCastException: cannot assign instance of scala.collection.immutable.List$SerializationProxy to field com.Table.rows of type scala.collection.immutable.List in instance of com.Table
java.lang.ClassCastException: cannot assign instance of scala.collection.immutable.List$SerializationProxy to field com.Table.rows of type scala.collection.immutable.List in instance of com.Table
at java.io.ObjectStreamClass$FieldReflector.setObjFieldValues(ObjectStreamClass.java:2133)
at java.io.ObjectStreamClass.setObjFieldValues(ObjectStreamClass.java:1305)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2024)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1942)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1808)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1353)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:373)
at com.TestSeri$.serializeBinDeserialise(TestSeri.scala:37)
at com.TestSeri$.main(TestSeri.scala:22)
at com.TestSeri.main(TestSeri.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
Here is the code
import java.io._
import scalax.file.Path
case class Row(name: String)
case class Table(rows: List[Row])
case class Cont(docs: Map[String, Table])
case object TestSeri {
def main(args: Array[String]) {
val cc = Cont(docs = List(
"1" -> Table(rows = List(Row("r1"), Row("r2"))),
"2" -> Table(rows = List(Row("r301"), Row("r31"), Row("r32")))
).toMap)
val tt = Table(rows = List(Row("r1"), Row("r2")))
val ttdes = serializeBinDeserialize(tt)
println(ttdes == tt)
val ccdes = serializeBinDeserialize(cc)
println(ccdes == cc)
}
def serializeBinDeserialize[T](payload: T): T = {
val bos = new ByteArrayOutputStream()
val out = new ObjectOutputStream(bos)
out.writeObject(payload)
val bis = new ByteArrayInputStream(bos.toByteArray)
val in = new ObjectInputStream(bis)
in.readObject().asInstanceOf[T]
}
}

Answer 1

Replacing List with Array which is immutable too, fixed the problem.
In my original problem I had a Map which I replaced with TreeMap.
I think is likely to be related to the proxy pattern implementation in generic immutable List and Map mentioned here:
https://issues.scala-lang.org/browse/SI-9237.
Can't believe I wasted a full day on this.