akka actor 的request-response简单实现

注：本文章是看blog后的一个阶段小结，只作为个人笔记，原文链接：http://www.iteblog.com/archives/1154

官网地址贴上：http://doc.akka.io/docs/akka/snapshot/scala/actors.html

在上篇文章中，我们写明了向actor发送消息的原理，而actor接收到消息后，能够作出response，这个回应可以是发送给发送消息的actor，也可以是别的actor，这里将讨论前者，场景描述如下：

上图传达了我们此刻想表达的意思。为了简单，我没有在图中画出ActorSystem、Dispatcher 和Mailboxes。

　　1、DriverApp个StudentActor发送了一个InitSignal消息；
　　2、StudentActor对InitSignal消息作出反应，并且发送了QuoteRequest 消息给TeacherActor；
　　3、TeacherActor用QuoteResponse作出了响应；

　　4、StudentActor仅仅将QuoteResponse 作为日志打印到控制台/logger。

第一步：由DriverApp 发起，代码如下：

//Initialize the ActorSystem

val system = ActorSystem("UniversityMessageSystem")

//create the teacher actor
val teacherRef = system.actorOf(Props[TeacherActor], "teacherActor")

//create the Student Actor -
//用TeacherActor 作为StudentActor构造参数，并传入到ActorRef 中，这样StudentActor 将可以用ActorRef发送消息到TeacherActor
val studentRef = system.actorOf(Props(new StudentActor(teacherRef)), "studentActor")

//send InitSignalto student actor
studentRef ! InitSignal

第二步：StudentActor 接收来自 DriverApp 的 InitSignal 消息，然后给TeacherActor发送一个QuoteRequest

def receive = {
    case InitSignal=> {
          teacherActorRef!QuoteRequest
    }
    ...

...

第三步：TeacherActor 对 StudentActor 作出响应

class TeacherActor extends Actor with ActorLogging {

val quotes = List(
    "Moderation is for cowards",
    "Anything worth doing is worth overdoing",
    "The trouble is you think you have time",
    "You never gonna know if you never even try")
  def receive = {
    case QuoteRequest => {
      import util.Random
      //Get a random Quote from the list and construct a response
      val quoteResponse = QuoteResponse(quotes(Random.nextInt(quotes.size)))
      //respond back to the Student who is the original sender of QuoteRequest
      sender ! quoteResponse
    }
  }
}

第四步：StudentActor仅仅将QuoteResponse 作为日志打印到控制台/logger

class StudentActor (teacherActorRef:ActorRef) extends Actor with ActorLogging {
def receive = {
    case InitSignal=> {
      teacherActorRef!QuoteRequest
    }
    case QuoteResponse(quoteString) => {
      log.info ("Received QuoteResponse from Teacher")
      log.info(s"Printing from Student Actor $quoteString")
    }
  }
}