Scala Akka事件采购如何将消息恢复到root？

Question

我目前努力阅读演员的状态，因此在这种情况下，我只想从我的州类中获取历史记录参数 - 例如，在调用端点时将其打印出来。

我已经成功地做到了吗？以前是运营商，但我从未尝试过使用事件采购。

到目前为止，我拥有的代码是：

object MyPersistentBehavior {
  sealed trait Command
  final case class Add(data: String) extends Command
  case object Clear extends Command

  sealed trait Event
  final case class Added(data: String) extends Event
  case object Cleared extends Event

  final case class State(history: List[String] = Nil)

  val commandHandler: (State, Command) => Effect[Event, State] = { (state, command) =>
    command match {
      case Add(data) => Effect.persist(Added(data))
      case Clear     => Effect.persist(Cleared)
    }
  }

  val eventHandler: (State, Event) => State = { (state, event) =>
    event match {
      case Added(data) => state.copy((data :: state.history).take(5))
      case Cleared     => State(Nil)
    }
  }

  def apply(id: String): Behavior[Command] =
    EventSourcedBehavior[Command, Event, State](
      persistenceId = PersistenceId.ofUniqueId(id),
      emptyState = State(Nil),
      commandHandler = commandHandler,
      eventHandler = eventHandler)
}

在我的主要方法中，我想打印状态：

val personActor: ActorSystem[MyPersistentBehavior.Command] = ActorSystem(MyPersistentBehavior("IDDD"), "AHA")
//personActor ? GetState <- something like this

谢谢！

Answer 1

我没有在Akka中与事件采购合作，而是在文档中快速查看，尽管我有帮助：

case class GetState(replyTo: ActorRef[StatusReply[AddPostDone]]) extends Command

// and in the match for commands:
...
    case GetState(replyTo) =>
      replyTo ! StatusReply.Success(state)

      // or if replyTo was of type ActorRef[State] => 
      replyTo ! state

还有此效果在Akka的事件采购文档中看起来很有趣：

def onCommand(subscriber: ActorRef[State], state: State, command: Command): Effect[Event, State] = {
  command match {
    case Add(data) =>
      Effect.persist(Added(data)).thenRun(newState => subscriber ! newState)
    case Clear =>
      Effect.persist(Cleared).thenRun((newState: State) => subscriber ! newState).thenStop()
  }
}

如您所见，非常易于使用。
您还可以在每次效果之后回复最新状态：

case class AddCommand(number: Int, replyTo: ActorRef[State]) extends Command

// in the command handler
    case add: AddCommand(num, replyTo) => 
      // your logic here
      Event.persist(Added(num)) thenRun { newState => 
        replyTo ! newState
      }

文档中还有很多其他选项，因此我强烈建议您查看： https://doc.akka.io/docs/akka/current/current/typed/persistence.html

Answer 2

好的，如果您需要一个完整的示例，请查看我的博客。

您将在博客和GitHub存储库中看到，在那里，您会看到所有演员向呼叫者报告他们的状态的通用“主持”命令。

    def commandHandler(context: ActorContext[CreditSMEvent], cmd: CreditSMEvent, state: State): ReplyEffect[PersistEvent, State] =
      cmd match {
        case onReport(useCaseKey, replyTo) =>
            Effect.reply(replyTo)( ReportResponse(state, java.util.Collections.unmodifiableMap(state.controlObject)))

        case _ =>
            commandHandlerInternal(context, cmd, state)
}

您可以在此点在博客中。

希望这对您有帮助。