There is a discussion in the mailing-list (http://h.yandex.net/?http%3A%2F%2Fgroups.google.com%2Fgroup%2Fakka-user%2Fbrowse_thread%2Fthread%2F3eb02532e6b9a91a%29) and I've decided to create a ticket.

I use akka 1.1.2. There is an example of Supervisor Hierarchies configuration in Spring: http://akka.io/docs/akka-modules/1.1.2/modules/spring.html#supervisor-hierarchies. It is unclear from the example whether implementation attribute of the akka:untyped-actor is a required attribute. I have the following example configuration based on Spring beans:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns:akka="http://akka.io/schema/akka"
      xsi:schemaLocation="
      http://www.springframework.org/schema/beans
      http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
      http://akka.io/schema/akka
      http://akka.io/akka-1.0.xsd">
   <bean id="myActorBean"
         class="MyActor"
         scope="prototype">
       <constructor-arg value="Test"/>
   </bean>

   <akka:supervision id="supervisor">
       <akka:restart-strategy failover="AllForOne"
                              retries="3"
                              timerange="4000">
           <akka:trap-exits>
               <akka:trap-exit>java.io.IOException</akka:trap-exit>
               <akka:trap-exit>java.lang.NullPointerException</akka:trap-exit>
           </akka:trap-exits>
       </akka:restart-strategy>
       <akka:untyped-actors>
           <akka:untyped-actor id="myActor"
                               ref="myActorBean"
                               autostart="true"
                               lifecycle="temporary"/>
       </akka:untyped-actors>
   </akka:supervision>
</beans>

When I start the application I get the following error:

Jun 29, 2011 3:33:51 PM org.springframework.context.support.AbstractApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@207f5580: startup date [Wed Jun 29 15:33:51 MSD 2011]; root of context hierarchy
Jun 29, 2011 3:33:51 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [test.xml]
Jun 29, 2011 3:33:53 PM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@2d20dbf3: defining beans [myActorBean,supervisor]; root of factory hierarchy
Jun 29, 2011 3:33:53 PM org.springframework.beans.factory.support.DefaultSingletonBeanRegistry destroySingletons
INFO: Destroying singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@2d20dbf3: defining beans [myActorBean,supervisor]; root of factory hierarchy
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'supervisor': Invocation of init method failed; nested exception is java.lang.IllegalArgumentException: Class name can't be null or empty string [null]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1420)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:291)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:288)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:190)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:563)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:895)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:425)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
	at com.yandex.etl.EntryPoint$delayedInit$body.apply(EntryPoint.scala:17)
	at scala.Function0$class.apply$mcV$sp(Function0.scala:34)
	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
	at scala.App$$anonfun$main$1.apply(App.scala:60)
	at scala.App$$anonfun$main$1.apply(App.scala:60)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:30)
	at scala.App$class.main(App.scala:60)
	at com.yandex.etl.EntryPoint$.main(EntryPoint.scala:12)
	at com.yandex.etl.EntryPoint.main(EntryPoint.scala)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
Caused by: java.lang.IllegalArgumentException: Class name can't be null or empty string [null]
	at akka.spring.StringReflect.<init>(StringReflect.scala:20)
	at akka.spring.StringReflect$.string2StringReflect(StringReflect.scala:12)
	at akka.spring.SupervisionFactoryBean.createSupervise(SupervisionFactoryBean.scala:84)
	at akka.spring.SupervisionFactoryBean$$anonfun$1.apply(SupervisionFactoryBean.scala:48)
	at akka.spring.SupervisionFactoryBean$$anonfun$1.apply(SupervisionFactoryBean.scala:48)
	at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:194)
	at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:194)
	at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
	at scala.collection.immutable.List.foreach(List.scala:45)
	at scala.collection.TraversableLike$class.map(TraversableLike.scala:194)
	at scala.collection.immutable.List.map(List.scala:45)
	at akka.spring.SupervisionFactoryBean.createInstanceForUntypedActors(SupervisionFactoryBean.scala:48)
	at akka.spring.SupervisionFactoryBean.createInstance(SupervisionFactoryBean.scala:32)
	at org.springframework.beans.factory.config.AbstractFactoryBean.afterPropertiesSet(AbstractFactoryBean.java:130)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1477)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1417)
	... 27 more

MyActor class:

class MyActor(val name: String) extends Actor {
 def receive = {
   case msg => EventHandler.info(self, "Received message: %s" format msg)
 }
}

I'm not sure that it is a bug. Then is it possible to implement this feature? Precisely how am I supposed to instantiate and supervise actors having non-default constructor using Spring? May be there is some way to define a supervisor and after that declaratively link actors to it in Spring.