Making sure that ActorCell isn't serializable

akka-actor-tests/src/test/scala/akka/serialization/SerializeSpec.scala

@@ -7,10 +7,9 @@ package akka.serialization
 import akka.serialization.Serialization._
 import scala.reflect._
 import akka.testkit.AkkaSpec
-import akka.actor.{ ActorSystem, ActorSystemImpl }
-import java.io.{ ObjectInputStream, ByteArrayInputStream, ByteArrayOutputStream, ObjectOutputStream }
-import akka.actor.DeadLetterActorRef
 import com.typesafe.config.ConfigFactory
+import akka.actor._
+import java.io._
 
 object SerializeSpec {
 
@@ -94,6 +93,22 @@ class SerializeSpec extends AkkaSpec(SerializeSpec.serializationConf) {
       }
     }
 
+    "not serialize ActorCell" in {
+      val a = system.actorOf(Props(new Actor {
+        def receive = {
+          case o: ObjectOutputStream ⇒
+            try {
+              o.writeObject(this)
+            } catch {
+              case _: NotSerializableException ⇒ testActor ! "pass"
+            }
+        }
+      }))
+      a ! new ObjectOutputStream(new ByteArrayOutputStream())
+      expectMsg("pass")
+      a.stop
+    }
+
     "serialize DeadLetterActorRef" in {
       val outbuf = new ByteArrayOutputStream()
       val out = new ObjectOutputStream(outbuf)

akka-actor/src/main/scala/akka/actor/Actor.scala

@@ -206,7 +206,6 @@ trait Actor {
    * [[akka.actor.UntypedActorContext]], which is the Java API of the actor
    * context.
    */
-  @transient
   protected[akka] implicit val context: ActorContext = {
     val contextStack = ActorCell.contextStack.get
 

akka-actor/src/main/scala/akka/actor/ActorCell.scala

@@ -12,6 +12,7 @@ import java.util.concurrent.TimeUnit.MILLISECONDS
 import akka.event.Logging.{ Debug, Warning, Error }
 import akka.util.{ Duration, Helpers }
 import akka.japi.Procedure
+import java.io.{ NotSerializableException, ObjectOutputStream }
 
 /**
  * The actor context - the view of the actor cell from the actor.
@@ -602,4 +603,7 @@ private[akka] final class ActorCell(
       lookupAndSetField(a.getClass, a, "self", self)
     }
   }
+
+  final protected def writeObject(o: ObjectOutputStream): Unit =
+    throw new NotSerializableException("ActorCell/ActorContext is not serializable!")
 }