Question

I would like to use Akka actors in Java.

I downloaded the akka-1.0.zip and added akka-actor-1.0.jar to my “Build Path” in Eclipse.

Then I wrote this Actor class:

package com.example;

import akka.actor.UntypedActor;

public class MyActor extends UntypedActor {

    public void onReceive(Object message) throws IllegalArgumentException {
        if (message instanceof String) {
            System.out.println("Received: " + message);
        } else throw new IllegalArgumentException("Unknown message: " + message);
    }
}

But I get errors in Eclipse:

The type scala.Option cannot be resolved.
The type scala.Some cannot be resolved.
The type scala.PartialFunction cannot be resolved.
The type scala.ScalaObject cannot be resoled.

Do I need to add any more files to my “Build Path” or what am I doing wrong? I don’t find the documentation beeing that helpful.

Update: I added scala-library.jar to my Build Path and the above erros disappeared. But I get an error when I compile and run the application:

Exception in thread "main" java.lang.NoClassDefFoundError: net/lag/configgy/ConfigMap
    at akka.actor.Actors.actorOf(Actors.java:70)
    at com.example.ActorTest.main(ActorTest.java:9)
Caused by: java.lang.ClassNotFoundException: net.lag.configgy.ConfigMap
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 2 more

Here is the main class where I use my actor:

package com.example;

import akka.actor.ActorRef;
import akka.actor.Actors;

public class ActorTest {

    public static void main(String[] args) {
        ActorRef myActor = Actors.actorOf(MyActor.class);
        myActor.start();
        System.out.println("My Actor started");
    }

}

Answer 1

In your akka-1.0.zip file there is scala-library.jar. Try adding it to the build path.

Also, there is a lib_managed directory inside the zip, which contains further library files. Possibly aslo some of them will be needed.

To avoid this kind of situations you should try maven. There is a Akka repository: http://scalablesolutions.se/akka/repository/se/scalablesolutions/akka/