Akka并发编程——2、Actor模型(二）

摘要： 本节主要内容： Actor API解析 1. Actor API解析 Actor中的主要成员变量和方法定义如下： package akka.actor trait Actor extends scala.AnyRef { type Receive = akka.actor.Actor.Receive //context变量暴露当前Actor的上下文信息

本节主要内容：

Actor API解析

Actor API解析

Actor中的主要成员变量和方法定义如下： package akka.actor trait Actor extends scala.AnyRef { type Receive = akka.actor.Actor.Receive //context变量暴露当前Actor的上下文信息及当前消息 implicit val context : akka.actor.ActorContext = { /* compiled code */ } //self作为当前ActorRef的引用 implicit final val self : akka.actor.ActorRef = { /* compiled code */ } //当前Actor接收到最后一条消息对应的消息发送者(Actor） final def sender() : akka.actor.ActorRef = { /* compiled code */ } //receive方法，抽象方法，定义Actor的行为逻辑 def receive : akka.actor.Actor.Receive //内部使用API protected[akka] def aroundReceive(receive : akka.actor.Actor.Receive, msg : scala.Any) : scala.Unit = { /* compiled code */ } protected[akka] def aroundPreStart() : scala.Unit = { /* compiled code */ } protected[akka] def aroundPostStop() : scala.Unit = { /* compiled code */ } protected[akka] def aroundPreRestart(reason : scala.Throwable, message : scala.Option[scala.Any]) : scala.Unit = { /* compiled code */ } protected[akka] def aroundPostRestart(reason : scala.Throwable) : scala.Unit = { /* compiled code */ } //监督策略，用于Actor容错处理 def supervisorStrategy : akka.actor.SupervisorStrategy = { /* compiled code */ } //Hook方法，用于Actor生命周期监控 @scala.throws[T](classOf[scala.Exception]) def preStart() : scala.Unit = { /* compiled code */ } @scala.throws[T](classOf[scala.Exception]) def postStop() : scala.Unit = { /* compiled code */ } @scala.throws[T](classOf[scala.Exception]) def preRestart(reason : scala.Throwable, message : scala.Option[scala.Any]) : scala.Unit = { /* compiled code */ } @scala.throws[T](classOf[scala.Exception]) def postRestart(reason : scala.Throwable) : scala.Unit = { /* compiled code */ } //发送给Actor的消息，Actor没有定义相应的处理逻辑时，会调用此方法 def unhandled(message : scala.Any) : scala.Unit = { /* compiled code */ } } object Actor extends scala.AnyRef { type Receive = scala.PartialFunction[scala.Any, scala.Unit] //空的行为逻辑 @scala.SerialVersionUID(1) object emptyBehavior extends scala.AnyRef with akka.actor.Actor.Receive { def isDefinedAt(x : scala.Any) : scala.Boolean = { /* compiled code */ } def apply(x : scala.Any) : scala.Nothing = { /* compiled code */ } } //Sender为null @scala.SerialVersionUID(1) final val noSender : akka.actor.ActorRef = { /* compiled code */ } }

（1） Hook方法中，preStart()、postStop()方法的使用

上面代码可以看出：Hook方法中，有四个子方法。这里主要关注前两个。

/* *Actor API: Hook方法 */ object Example_05 extends App{ import akka.actor.Actor import akka.actor.ActorSystem import akka.actor.Props class FirstActor extends Actor with ActorLogging{ //通过context.actorOf方法创建Actor var child:ActorRef = _ //Hook方法，preStart()，Actor启动之前调用，用于完成初始化工作 override def preStart(): Unit ={ log.info("preStart() in FirstActor") //通过context上下文创建Actor child = context.actorOf(Props[MyActor], name = "myChild") } def receive = { //向MyActor发送消息 case x => child ! x;log.info("received "+x) } //Hook方法，postStop()，Actor停止之后调用 override def postStop(): Unit = { log.info("postStop() in FirstActor") } } class MyActor extends Actor with ActorLogging{ //Hook方法，preStart()，Actor启动之前调用，用于完成初始化工作 override def preStart(): Unit ={ log.info("preStart() in MyActor") } def receive = { case "test" => log.info("received test") case _ => log.info("received unknown message") } //Hook方法，postStop()，Actor停止之后调用 override def postStop(): Unit = { log.info("postStop() in MyActor") } } val system = ActorSystem("MyActorSystem") val systemLog=system.log //创建FirstActor对象 val myactor = system.actorOf(Props[FirstActor], name = "firstActor") systemLog.info("准备向myactor发送消息") //向myactor发送消息 myactor!"test" myactor! 123 Thread.sleep(5000) //关闭ActorSystem，停止程序的运行 system.shutdown() } 代码运行结果：

[INFO] [04/02/2016 17:04:49.607] [main] [ActorSystem(MyActorSystem)] 准备向myactor发送消息 [INFO] [04/02/2016 17:04:49.607] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor] preStart() in FirstActor [INFO] [04/02/2016 17:04:49.607] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor] received test [INFO] [04/02/2016 17:04:49.607] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor] received 123 [INFO] [04/02/2016 17:04:49.608] [MyActorSystem-akka.actor.default-dispatcher-2] [akka://MyActorSystem/user/firstActor/myChild] preStart() in MyActor [INFO] [04/02/2016 17:04:49.608] [MyActorSystem-akka.actor.default-dispatcher-2] [akka://MyActorSystem/user/firstActor/myChild] received test [INFO] [04/02/2016 17:04:49.608] [MyActorSystem-akka.actor.default-dispatcher-2] [akka://MyActorSystem/user/firstActor/myChild] received unknown message [INFO] [04/02/2016 17:04:54.616] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor/myChild] postStop() in MyActor [INFO] [04/02/2016 17:04:54.617] [MyActorSystem-akka.actor.default-dispatcher-3] [akka://MyActorSystem/user/firstActor] postStop() in FirstActor 其中 FirstActor为顶级Actor，MyActor为FirstActor的子进程：

class FirstActor extends Actor with ActorLogging{ //通过context.actorOf方法创建Actor var child:ActorRef = _ //Hook方法，preStart()，Actor启动之前调用，用于完成初始化工作 override def preStart(): Unit ={ log.info("preStart() in FirstActor") //通过context上下文创建Actor child = context.actorOf(Props[MyActor], name = "myChild") } def receive = { //向MyActor发送消息 case x => child ! x;log.info("received "+x) } //Hook方法，postStop()，Actor停止之后调用，用于完成初始化工作 override def postStop(): Unit = { log.info("postStop() in FirstActor") } } 对preStart()和postStop()方法进行了重写。 在preStart方法中通过代码:

child = context.actorOf(Props[MyActor], name = "myChild") 对成员变量child进行初始化，然后在postStop方法中使用

//通过context上下文停止MyActor的运行 context.stop(child) 来停止MyActor的运行。

此外，对创建FirstActor的时候：

//创建FirstActor对象 val myactor = system.actorOf(Props[FirstActor], name = "firstActor")会首先调用其preStart方法，而其preStart方法除了打印日志: " preStart() in FirstActor"外，还创建了其子Actor ：MyActor。

在创建MyActor的过程中，也调用其preStart方法。

注意，最后关闭的时候：

//关闭ActorSystem，停止程序的运行 system.shutdown() FirstActor作为MyActor的Supervisor，会先停止MyActor，再停止自身，因此先调用MyActor的postStop方法，再调用FirstActor的postStop方法。

（2） 成员变量self及成员方法sender方法的使用

/* *Actor API:成员变量self及sender()方法的使用 */ object Example_05 extends App{ import akka.actor.Actor import akka.actor.ActorSystem import akka.actor.Props class FirstActor extends Actor with ActorLogging{ //通过context.actorOf方法创建Actor var child:ActorRef = _ override def preStart(): Unit ={ log.info("preStart() in FirstActor") //通过context上下文创建Actor child = context.actorOf(Props[MyActor], name = "myActor") } def receive = { //向MyActor发送消息 case x => child ! x;log.info("received "+x) } } class MyActor extends Actor with ActorLogging{ self!"message from self reference" def receive = { case "test" => log.info("received test");sender()!"message from MyActor" case "message from self reference"=>log.info("message from self refrence") case _ => log.info("received unknown message"); } } val system = ActorSystem("MyActorSystem") val systemLog=system.log //创建FirstActor对象 val myactor = system.actorOf(Props[FirstActor], name = "firstActor") systemLog.info("准备向myactor发送消息") //向myactor发送消息 myactor!"test" myactor! 123 Thread.sleep(5000) //关闭ActorSystem，停止程序的运行 system.shutdown() } 运行结果：

[INFO] [04/02/2016 18:40:37.805] [main] [ActorSystem(MyActorSystem)] 准备向myactor发送消息 [INFO] [04/02/2016 18:40:37.805] [MyActorSystem-akka.actor.default-dispatcher-3] [akka://MyActorSystem/user/firstActor] preStart() in FirstActor [INFO] [04/02/2016 18:40:37.806] [MyActorSystem-akka.actor.default-dispatcher-3] [akka://MyActorSystem/user/firstActor] received test [INFO] [04/02/2016 18:40:37.806] [MyActorSystem-akka.actor.default-dispatcher-3] [akka://MyActorSystem/user/firstActor] received 123 [INFO] [04/02/2016 18:40:37.806] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor/myActor] received test [INFO] [04/02/2016 18:40:37.806] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor/myActor] message from self refrence [INFO] [04/02/2016 18:40:37.806] [MyActorSystem-akka.actor.default-dispatcher-3] [akka://MyActorSystem/user/firstActor] received message from MyActor [INFO] [04/02/2016 18:40:37.806] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor/myActor] received unknown message [INFO] [04/02/2016 18:40:37.806] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor/myActor] received unknown message 代码： class MyActor extends Actor with ActorLogging{ self!"message from self reference" def receive = { case "test" => log.info("received test");sender()!"message from MyActor" case "message from self reference"=>log.info("message from self refrence") case _ => log.info("received unknown message"); } } 中使用

self!"message from self reference"即向自己发送了一条消息，receive方法通过下面这条语句 对这条消息进行处理。

case "message from self reference"=>log.info("message from self refrence")而在处理

case "test" => log.info("received test");sender()!"message from MyActor" 的时候， sender()是FirstActor，即向FirstActor发送消息：“message from MyActor”。

注意：有的朋友可能会问，为什么最后会有两个received unknown message？

其中一个是myActor!123，还有一个是由sender()传给FirstActor的，即把由myActor传过来的“message from MyActor”经由FirstActor再次传递给MyActor。

（3） unhandled方法的使用

unhandled方法用于处理没有被receive方法处理的消息，下面的代码给出的是当不重写unhandled方法时的代码

这里不再赘述，详情请见：Akka阿里云