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.actortrait 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