Akka/Scala example source code file (ActorSystemActivator.scala)

This example Akka source code file (ActorSystemActivator.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Akka and Scala source code examples by using tags.

All credit for the original source code belongs to akka.io; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Akka tags/keywords

actor, actorsystem, akka, bundleactivator, bundlecontext, cleanup, none, option, osgi, servicelistener, string, t, unit

The ActorSystemActivator.scala Akka example source code

/**
 * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
 */
package akka.osgi

import akka.actor.ActorSystem
import java.util.{ Dictionary, Properties }
import org.osgi.framework._
import org.osgi.service.log.LogService
import com.typesafe.config.{ ConfigFactory, Config }

/**
 * Abstract bundle activator implementation to bootstrap and configure an actor system in an
 * OSGi environment.  It also provides a convenience method to register the actor system in
 * the OSGi Service Registry for sharing it with other OSGi bundles.
 *
 * This convenience activator is mainly useful for setting up a single [[akka.actor.ActorSystem]] instance and sharing that
 * with other bundles in the OSGi Framework.  If you want to set up multiple systems in the same bundle context, look at
 * the [[akka.osgi.OsgiActorSystemFactory]] instead.
 */
abstract class ActorSystemActivator extends BundleActivator {

  private var system: Option[ActorSystem] = None
  private var registration: Option[ServiceRegistration[_]] = None

  /**
   * Implement this method to add your own actors to the ActorSystem.  If you want to share the actor
   * system with other bundles, call the `registerService(BundleContext, ActorSystem)` method from within
   * this method.
   *
   * @param context the bundle context
   * @param system the ActorSystem that was created by the activator
   */
  def configure(context: BundleContext, system: ActorSystem): Unit

  /**
   * Sets up a new ActorSystem
   *
   * @param context the BundleContext
   */
  def start(context: BundleContext): Unit = {
    system = Some(OsgiActorSystemFactory(context, getActorSystemConfiguration(context)).createActorSystem(Option(getActorSystemName(context))))
    system foreach (addLogServiceListener(context, _))
    system foreach (configure(context, _))
  }

  /**
   * Adds a LogService Listener that will advertise the ActorSystem on LogService registration and unregistration
   *
   * @param context  the BundleContext
   * @param  system  the ActorSystem to be advertised
   */
  def addLogServiceListener(context: BundleContext, system: ActorSystem) {
    val logServiceListner = new ServiceListener {
      def serviceChanged(event: ServiceEvent) {
        event.getType match {
          case ServiceEvent.REGISTERED ⇒
            system.eventStream.publish(serviceForReference[LogService](context, event.getServiceReference))
          case ServiceEvent.UNREGISTERING ⇒ system.eventStream.publish(UnregisteringLogService)
        }
      }
    }
    val filter = s"(objectclass=${classOf[LogService].getName})"
    context.addServiceListener(logServiceListner, filter)

    //Small trick to create an event if the service is registred before this start listing for
    Option(context.getServiceReference(classOf[LogService].getName)).foreach(x ⇒ {
      logServiceListner.serviceChanged(new ServiceEvent(ServiceEvent.REGISTERED, x))
    })
  }

  /**
   * Convenience method to find a service by its reference.
   */
  def serviceForReference[T](context: BundleContext, reference: ServiceReference[_]): T =
    context.getService(reference).asInstanceOf[T]

  /**
   * Shuts down the ActorSystem when the bundle is stopped and, if necessary, unregisters a service registration.
   *
   * @param context the BundleContext
   */
  def stop(context: BundleContext): Unit = {
    registration foreach (_.unregister())
    system foreach (_.shutdown())
  }

  /**
   * Register the actor system in the OSGi service registry.  The activator itself will ensure that this service
   * is unregistered again when the bundle is being stopped.
   *
   * Only one ActorSystem can be registered at a time, so any previous registration will be unregistered prior to registering the new.
   *
   * @param context the bundle context
   * @param system the actor system
   */
  def registerService(context: BundleContext, system: ActorSystem): Unit = {
    registration.foreach(_.unregister()) //Cleanup
    val properties = new Properties()
    properties.put("name", system.name)
    registration = Some(context.registerService(classOf[ActorSystem].getName, system,
      properties.asInstanceOf[Dictionary[String, Any]]))
  }

  /**
   * By default, the [[akka.actor.ActorSystem]] name will be set to `bundle-<bundle id>-ActorSystem`.  Override this
   * method to define another name for your [[akka.actor.ActorSystem]] instance.
   *
   * @param context the bundle context
   * @return the actor system name
   */
  def getActorSystemName(context: BundleContext): String = null

  /**
   * Override this method to define a configuration for your [[akka.actor.ActorSystem]] instance.
   * This configuration will be merged with fallback on
   *    the application.conf of your bundle
   *    the reference.conf of the akka bundles
   *    the System properties.
   *
   * @param context the bundle context
   * @return the actor system specific configuration, ConfigFactory.empty by default
   */
  def getActorSystemConfiguration(context: BundleContext): Config = ConfigFactory.empty

}