java - De-/Serializing with readObject/writeObject -

i'm having bit of struggle these writeobject/readobject methods.

let's have a

trait abstractposition{     def file:path     def start:string     def end:string } 

with

class sourceposition(val: path, val start:string, val end:string)     extends abstractposition object sourceposition {   def apply(file: path, start: string, end: string) =     new sourceposition(file, start, some(end))    def unapply(sp: sourceposition) = some((sp.file, sp.start, sp.end)) } 

and have store such positions file. naive attempt fails because path objects not serializable:

java.io.notserializableexception: ... .sourceposition

so rewrite:

trait abstractposition extends serializable{     def file:path     def start:string     def end:string }  class sourceposition(@transient var filearg: path, val start:string, val end:string)     extends abstractposition{    private var filestring :string = null   override def file: path = this.filearg    @throws(classof[ioexception])   private def writeobject(out: objectoutputstream): unit = {     filestring = file.tostring     out.defaultwriteobject()   }    @throws(classof[ioexception])   private def readobject(in: objectinputstream): unit = {     in.defaultreadobject()     filearg = paths.get(filestring)   } object sourceposition {   def apply(file: path, start: string, end: string) =     new sourceposition(file, start, some(end))    def unapply(sp: sourceposition) = some((sp.file, sp.start, sp.end)) } 

but no avail:

java.io.notserializableexception: sun.nio.fs.windowspath$windowspathwithattributes

what doing wrong?

and how can achieve i'm trying do?

make sourceposition case class: it's perfect candidate it's immutable. case classes serializable default without writeobject/readobject stuff. bonus apply/unapply methods generated automatically scalac.