NotSerializableException for `Map[String, String]` alias

Question

I'm trying to send an object to a remote actor and I got this exception: ``` ERROR akka.remote.EndpointWriter - Transient association error (association remains live) java.io.NotSerializableException: scala.collection.immutable.MapLike$$anon$2 ``` The object being serialized is a case class: ``` case class LocationReport(idn: String, report: String, timestamp: Option[String], location: Attr, status: Attr, alarms: Attr, network: Attr, sensors: Attr) extends Message(idn) { val ts = timestamp getOrElse location("fix_timestamp") def json = (report -> ("TIME" -> ts) ~ ("location" -> location) ~ ("alarms" -> alarms) ~ ("network" -> network) ~ ("sensors" -> ((status ++ sensors) + ("CUSTOMCLOCK" -> Report.decodeTimestamp(ts))))) } ``` And `Attr` is a type re-definition: ``` type Attr = Map[String, String] ``` The `Message` class is pretty simple: ``` abstract class Message(idn: String) { def topic = idn def json(): JValue } ``` I'm wondering if the type alias/redefinition is confusing the ser…

Accepted Answer

The problem is that `Map.mapValues` produces an object that's not serializable. When alarms was created, it's run through something like `alarms.mapValues(hex2Int)`. The problem and workaround is described here:

https://issues.scala-lang.org/browse/SI-7005

In short, the solution is to do `alarms.mapValues(hex2Int).map(identity)`

NotSerializableException for `Map[String, String]` alias

Solution

Problem