a scala remote actor exception - scala

Question

i with a scala code like this for echo service.
import scala.actors.Actor
import scala.actors.Actor._
import scala.actors.remote.RemoteActor._
class Echo extends Actor {
def act() {
alive(9010)
register('myName, self)
loop {
react {
case msg => println(msg)
}
}
}
}
object EchoServer {
def main(args: Array[String]): unit = {
val echo = new Echo
echo.start
println("Echo server started")
}
}
EchoServer.main(null)
but there has some exception.
java.lang.NoClassDefFoundError: Main$$anon$1$Echo$$anonfun$act$1
at Main$$anon$1$Echo.act((virtual file):16)
at scala.actors.Reaction.run(Reaction.scala:76)
at scala.actors.Actor$$anonfun$start$1.apply(Actor.scala:785)
at scala.actors.Actor$$anonfun$start$1.apply(Actor.scala:783)
at scala.actors.FJTaskScheduler2$$anon$1.run(FJTaskScheduler2.scala:160)
at scala.actors.FJTask$Wrap.run(Unknown Source)
at scala.actors.FJTaskRunner.scanWhileIdling(Unknown Source)
at scala.actors.FJTaskRunner.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException: Main$$anon$1$Echo$$anonfun$act$1
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
... 8 more
i don't konw how can cause it.
by the way .my scala version is 2.7.5

Answer 1

ClassNotFoundException indicates that something was probably not compiled, that should have been compiled. How did you compile it? Manually using scalac?
Try the following rm *.class scalac *.scala scala EchoServer.
The following works:
EchoServer.scala
import scala.actors.Actor
import scala.actors.Actor._
import scala.actors.remote.RemoteActor._
class Echo extends Actor {
def act() {
alive(9010)
register('myName, self)
loop {
react {
case msg => println(msg)
}
}
}
}
object EchoServer {
def main(args: Array[String]): unit = {
val echo = new Echo
echo.start
println("Echo server started")
}
}
Client.scala
import scala.actors.Actor._
import scala.actors.remote.Node
import scala.actors.remote.RemoteActor._
object Client extends Application {
override def main(args: Array[String]) {
if (args.length < 1) {
println("Usage: scala Client [msg]")
return
}
actor {
val remoteActor = select(Node("localhost", 9010), 'myName)
remoteActor !? args(0) match {
case msg => println( "Server's response is [" + msg + "]" )
}
}
}
}
Command line:
rm *.class && scalac *.scala && scala EchoServer
And in other terminal:
scala Client hello

Answer 2

You need to set the classloader on the remote actors.
Before the act() method, add the line:
RemoteActor.classLoader = getClass.getClassLoader
Why is setting the classloader necessary with Scala RemoteActors?