Akka併發程式設計——第三節:Actor模型(二)
本節主要內容:
- Actor API解析
1. Actor API解析
Actor中的主要成員變數和方法定義如下:
package akka.actor
trait Actor extends scala.AnyRef {
type Receive = akka.actor.Actor.Receive
//context變數暴露當前Actor的上下文資訊及當前訊息
implicit val context : akka.actor.ActorContext = { /* compiled code */ }
//self作為當前ActorRef的引用
implicit final val self : akka.actor.ActorRef = { /* compiled code */ }
//當前Actor接收到最後一條訊息對應的訊息傳送者(Actor)
final def sender() : akka.actor.ActorRef = { /* compiled code */ }
//receive方法,抽象方法,定義Actor的行為邏輯
def receive : akka.actor.Actor.Receive
//內部使用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 */ }
//監督策略,用於Actor容錯處理
def supervisorStrategy : akka.actor.SupervisorStrategy = { /* compiled code */ }
//Hook方法,用於Actor生命週期監控
@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 */ }
//傳送給Actor的訊息,Actor沒有定義相應的處理邏輯時,會呼叫此方法
def unhandled(message : scala.Any) : scala.Unit = { /* compiled code */ }
}
object Actor extends scala.AnyRef {
type Receive = scala.PartialFunction[scala.Any, scala.Unit]
//空的行為邏輯
@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為null
@scala.SerialVersionUID(1)
final val noSender : akka.actor.ActorRef = { /* compiled code */ }
}
(1) Hook方法,preStart()、postStop()方法的使用
/*
*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{
//通過context.actorOf方法建立Actor
var child:ActorRef = _
//Hook方法,preStart(),Actor啟動之前呼叫,用於完成初始化工作
override def preStart(): Unit ={
log.info("preStart() in FirstActor")
//通過context上下文建立Actor
child = context.actorOf(Props[MyActor], name = "myChild")
}
def receive = {
//向MyActor傳送訊息
case x => child ! x;log.info("received "+x)
}
//Hook方法,postStop(),Actor停止之後呼叫
override def postStop(): Unit = {
log.info("postStop() in FirstActor")
}
}
class MyActor extends Actor with ActorLogging{
//Hook方法,preStart(),Actor啟動之前呼叫,用於完成初始化工作
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停止之後呼叫
override def postStop(): Unit = {
log.info("postStop() in MyActor")
}
}
val system = ActorSystem("MyActorSystem")
val systemLog=system.log
//建立FirstActor物件
val myactor = system.actorOf(Props[FirstActor], name = "firstActor")
systemLog.info("準備向myactor傳送訊息")
//向myactor傳送訊息
myactor!"test"
myactor! 123
Thread.sleep(5000)
//關閉ActorSystem,停止程式的執行
system.shutdown()
}
程式碼執行結果:
[INFO] [04/02/2016 17:04:49.607] [main] [ActorSystem(MyActorSystem)] 準備向myactor傳送訊息
[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
在程式碼
class FirstActor extends Actor with ActorLogging{
//通過context.actorOf方法建立Actor
var child:ActorRef = _
//Hook方法,preStart(),Actor啟動之前呼叫,用於完成初始化工作
override def preStart(): Unit ={
log.info("preStart() in FirstActor")
//通過context上下文建立Actor
child = context.actorOf(Props[MyActor], name = "myChild")
}
def receive = {
//向MyActor傳送訊息
case x => child ! x;log.info("received "+x)
}
//Hook方法,postStop(),Actor停止之後呼叫,用於完成初始化工作
override def postStop(): Unit = {
log.info("postStop() in FirstActor")
}
}
中分別對postStop、preStart方法進行了重寫,在preStart方法中通過程式碼
child = context.actorOf(Props[MyActor], name = "myChild")
對成員變數child進行初始化,然後在postStop方法中使用
//通過context上下文停止MyActor的執行
context.stop(child)
停止MyActor的執行。在使用程式碼
//建立FirstActor物件
val myactor = system.actorOf(Props[FirstActor], name = "firstActor")
建立FirstActor時,便會呼叫preStart方法完成MyActor的建立,因此首先會執行FirstActor中的preStart()方法
dispatcher-4] [akka://MyActorSystem/user/firstActor] preStart() in FirstActor
然後在建立MyActor時執行MyActor中定義的preStart方法
[INFO] [04/02/2016 17:04:49.608] [MyActorSystem-akka.actor.default-dispatcher-2] [akka://MyActorSystem/user/firstActor/myChild] preStart() in MyActor
在執行
//關閉ActorSystem,停止程式的執行
system.shutdown()
FirstActor作為MyActor的Supervisor,會先停止MyActor,再停止自身,因此先呼叫MyActor的postStop方法,再呼叫FirstActor的postStop方法。
(2) 成員變數self及成員方法sender方法的使用
整體程式碼如下:
/*
*Actor API:成員變數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{
//通過context.actorOf方法建立Actor
var child:ActorRef = _
override def preStart(): Unit ={
log.info("preStart() in FirstActor")
//通過context上下文建立Actor
child = context.actorOf(Props[MyActor], name = "myActor")
}
def receive = {
//向MyActor傳送訊息
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
//建立FirstActor物件
val myactor = system.actorOf(Props[FirstActor], name = "firstActor")
systemLog.info("準備向myactor傳送訊息")
//向myactor傳送訊息
myactor!"test"
myactor! 123
Thread.sleep(5000)
//關閉ActorSystem,停止程式的執行
system.shutdown()
}
執行結果:
[INFO] [04/02/2016 18:40:37.805] [main] [ActorSystem(MyActorSystem)] 準備向myactor傳送訊息
[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
程式碼:
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"
向自身傳送了一條訊息,receive方法通過
case "message from self reference"=>log.info("message from self refrence")
對這條訊息進行處理。receive方法在處理
def receive = {
case "test" => log.info("received test");sender()!"message from MyActor"
“test”訊息時,會呼叫
sender()!"message from MyActor"
向sender(本例中為FirstActor)傳送”message from MyActor”訊息,FirstActor使用
def receive = {
//向MyActor傳送訊息
case x => child ! x;log.info("received "+x)
}
處理訊息時又向MyActor回送該訊息,因此最終的輸出有兩個unknown message,分別對應123和”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
(3) unhandled方法的使用
unhandled方法用於處理沒有被receive方法處理的訊息,下面的程式碼給出的是當不重寫unhandled方法時的程式碼
/*
*Actor API:unhandled方法
*/
object Example_06 extends App{
import akka.actor.Actor
import akka.actor.ActorSystem
import akka.actor.Props
class FirstActor extends Actor with ActorLogging{
def receive = {
//向MyActor傳送訊息
case "test" => log.info("received test")
}
}
val system = ActorSystem("MyActorSystem")
val systemLog=system.log
//建立FirstActor物件
val myactor = system.actorOf(Props[FirstActor], name = "firstActor")
systemLog.info("準備向myactor傳送訊息")
//向myactor傳送訊息
myactor!"test"
myactor! 123
Thread.sleep(5000)
//關閉ActorSystem,停止程式的執行
system.shutdown()
}
程式碼輸出:
[INFO] [04/02/2016 19:14:11.992] [main] [ActorSystem(MyActorSystem)] 準備向myactor傳送訊息
[INFO] [04/02/2016 19:14:11.992] [MyActorSystem-akka.actor.default-dispatcher-3] [akka://MyActorSystem/user/firstActor] received test
不難看出,對於
myactor! 123
傳送的這條訊息沒有被處理,沒有任何的處理邏輯。在實際開發過程中,可能會對不能被處理的訊息增加一些應對邏輯,此時可以重寫unhandled方法,程式碼如下:
/*
*Actor API:unhandled方法的使用
*/
object Example_06 extends App{
import akka.actor.Actor
import akka.actor.ActorSystem
import akka.actor.Props
class FirstActor extends Actor with ActorLogging{
def receive = {
//向MyActor傳送訊息
case "test" => log.info("received test")
}
//重寫unhandled方法
override def unhandled(message: Any): Unit = {
log.info("unhandled message is {}",message)
}
}
val system = ActorSystem("MyActorSystem")
val systemLog=system.log
//建立FirstActor物件
val myactor = system.actorOf(Props[FirstActor], name = "firstActor")
systemLog.info("準備向myactor傳送訊息")
//向myactor傳送訊息
myactor!"test"
myactor! 123
Thread.sleep(5000)
//關閉ActorSystem,停止程式的執行
system.shutdown()
}
程式碼輸出結果:
[INFO] [04/02/2016 19:17:18.458] [main] [ActorSystem(MyActorSystem)] 準備向myactor傳送訊息
[INFO] [04/02/2016 19:17:18.458] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor] received test
[INFO] [04/02/2016 19:17:18.458] [MyActorSystem-akka.actor.default-dispatcher-4] [akka://MyActorSystem/user/firstActor] unhandled message is 123
其它如preRestart等方法的使用將在Akka容錯部分進行講解。
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