Akka扩展有什么好处？

Question

我对Akka很新,并试图了解如何处理依赖注入.我遇到了这个考试,它引导我进入Akka扩展,现在我试图理解它与简单的静态方法调用有何不同.关于扩展的Akka教程部分有这样的例子:

public class CountExtensionImpl implements Extension {

    private final AtomicLong counter = new AtomicLong(0);

    public long increment() {
        return counter.incrementAndGet();
    }
}

public class CountExtension extends AbstractExtensionId<CountExtensionImpl> implements ExtensionIdProvider {

    public static final CountExtension EXTENSION = new CountExtension();

    private CountExtension() {

    }

    @Override
    public CountExtensionImpl createExtension(ExtendedActorSystem system) {
        return new CountExtensionImpl();
    }

    @Override
    public ExtensionId<? extends Extension> lookup() {
        return EXTENSION;
    }
}

public class MyActor extends UntypedActor{


    @Override
    public void onReceive(Object message) throws Exception {
        System.out.println(CountExtension.EXTENSION.get(getContext().system()).increment());

    }
}

但我无法理解简单的单例或静态方法有哪些优点？例如

public class MyActor extends UntypedActor{

    @Override
    public void onReceive(Object message) throws Exception {
        Counter.increment();

    }
}

Answer 1

Akka扩展绑定到ActorSystem,因此是每个系统的单例而不是全局单例.