public interface Extension
ActorSystem.registerExtension(...)
or by
specifying the corresponding option in the configuration passed to
ActorSystem, which will then instantiate (without arguments) each FQCN and
register the result.
The extension itself can be created in any way desired and has full access to the ActorSystem implementation.
This trait is only a marker interface to signify an Akka Extension. This is how an extension is normally constructed.
Scala API:
object MyExt extends ExtensionId[Ext] with ExtensionIdProvider {
override def lookup = MyExt
override def createExtension(system: ExtendedActorSystem): Ext = new Ext(system)
// Java API: retrieve the extension for the given system.
override def get(system: ActorSystem): UdpExt = super.get(system)
}
class Ext(system: ExtendedActorSystem) extends Extension {
...
}
Java API:
public class MyExt extends AbstractExtensionId<MyExtImpl>
implements ExtensionIdProvider {
public final static MyExt MyExtProvider = new MyExt();
private MyExt() {}
public MyExt lookup() {
return MyExt.MyExtProvider;
}
public MyExtImpl createExtension(ExtendedActorSystem system) {
return new MyExtImpl();
}
}
public class MyExtImpl implements Extension {
...
}
See also ExtensionKey
for a concise way of formulating extensions.