在 akka scala actor 中使用单例
我有一个演员将调用委托给有状态的单例。单例是有状态的，因为它维护对象的映射。这个单例对象仅在参与者和类（不是参与者）中使用，我在其中检索此映射中的一个对象（因此只是线程安全读取）。
class MyActor extends Actor{
def receive()={
case ACase => singleton.amethod()
case BCase => singleton.bmethod()
}
}
val singleton = new MyActorLogic
class MyActorLogic{
val map:Map[String, Object] = Map()
def amethod()=//alter the map
def readMap(value:String) = map(value) }
会有任何副作用/问题吗？ 谢谢
I have an actor that is delegating calls to a stateful singleton. The singleton is stateful since it is maintaining a map of objects. This singleton object is used just in the actor and in a class (not actor) where I am retrieving one object in this map (so just thread safe read).
class MyActor extends Actor{
def receive()={
case ACase => singleton.amethod()
case BCase => singleton.bmethod()
}
}
val singleton = new MyActorLogic
class MyActorLogic{
val map:Map[String, Object] = Map()
def amethod()=//alter the map
def readMap(value:String) = map(value) }
Could there be any side effects/problems?
Thanks
如果你对这篇内容有疑问，欢迎到本站社区发帖提问 参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。
绑定邮箱获取回复消息
由于您还没有绑定你的真实邮箱，如果其他用户或者作者回复了您的评论，将不能在第一时间通知您！
发布评论
评论（2）
无论出于何种原因，都不要这样做。
相信我。
如果您需要这类东西，请使用 Agent，这就是它们的优点：
http: //doc.akka.io/docs/akka/2.0.4/scala/agents.html
Do not do that for any reason in the world.
Trust me.
If you need that sort of things use Agent instead, that's what they are good for:
http://doc.akka.io/docs/akka/2.0.4/scala/agents.html
理论上，从多个线程使用带有简单可变映射的 MyActorLogic 可能会导致并发修改异常（当一个线程正在遍历映射，而另一个线程正在修改它时）。
您可以执行以下操作来避免出现问题：
Akka中，您不直接使用Actor实例（而是通过代理 -ActorRef访问它）。在这种情况下，对映射的安全访问不仅由始终一次处理一条消息的参与者保证 - 其他线程即使通过反射也无法访问私有成员。MyActorLogic的更新/检索方法成为线程安全的（例如，使它们同步）。ConcurrentHashMapvar map:immutable.Map。因此，访问map的多个线程有时可能会处理过时的数据，但不会有并发修改（写时复制方法）。只是为了说明，真正的单例是：
In theory, using
MyActorLogic, armed with a simple mutable map, from multiple threads, may lead to concurrent modification exception (when one thread is traversing the map, whilst another's modifying it).You could do the following to avoid problems :
Akka, you're not working with theActorinstance directly (but rather accessing it through a proxy -ActorRef). In this case, safe access to the map will not only be guaranteed by the actor, that always processes one message at a time - other threads won't be able to access private members even through reflection.MyActorLogicthread-safe (e.g., making themsynchronized)ConcurrentHashMapval map:mutable.Mapyou can usevar map:immutable.Map. Thus, multiple threads accessingmapmay occasionally work with a stale data, but there will be no concurrent modifications (copy-on-write approach).Just for the note, true singleton would be: