Akka 是一个用 Scala 编写的库,用于简化编写容错的、高可伸缩性的 Java 和 Scala 的 Actor 模型应用

 1.基于Actor的模型,我们大家都知道,在多线程领域,最困难的莫过于并发了,我们一般情况下处理并发会涉及到共享变量的问题,这样很容易造成死锁,模型如下:

Akka简介以及入门案例

而Akka是基于消息的Actor模型,Actor是具有属性和操作的,所有的操作都在Actor自身来完成,所以不存共享数据的问题

 
Akka简介以及入门案例

这里Actor A和B之间的通信是以消息的方式进行通信,每一个操作都是在Actor的内部完成的,所以不存在资源竞争的问题。

另外,Actor是为分布式的应用服务了

 

下面看一个例子

首先编写服务端代码:

import akka.actor.ActorSystem
import akka.actor.Actor
import akka.actor.Props
import com.typesafe.config.ConfigFactory
import akka.actor.ActorRef

object HelloRemote extends App {
  var akkaConf = ConfigFactory.parseString(
    s"""
      |akka.actor.provider = "akka.remote.RemoteActorRefProvider"
      |akka.remote.netty.tcp.transport-class = "akka.remote.transport.netty.NettyTransport"
      |akka.remote.netty.tcp.hostname = "127.0.0.1"
      |akka.remote.netty.tcp.port = 5160
      """.stripMargin)
  val actorSystem = ActorSystem("remotetest", akkaConf)
  val remoteActor = actorSystem.actorOf(Props[RemoteActor], name = "remoteActor")
  println(remoteActor)
  remoteActor.tell("START", ActorRef.noSender)
}
class RemoteActor extends Actor {
  def receive = {
    case "START" =>
      println("RemoteActor started ")
    case msg: String =>
      println(s"RemoteActor received message '$msg'")
      sender ! "reply from the RemoteActor"
  }
}

 这里RomoteActor是Actor的定义,所有的Actor都要继承Actor

receive 方法为需要自己实现的方法,这个方法内部定义了接收到消息后该做如何的处理

(这里是使用Scala语言实现的,Scala语言和java语言的不同点之一,就是case语句执行后不会继续往下执行)

这里我们定义了两类消息:

消息一:字符串等于START,这样是为了方便启动这个Actor

消息二:字符串类型消息,这样就接收所有的消息,然后进行回复。

sender是发送者actor的句柄,这样就能像发送者返回消息

我们启动这个remoteActor:

 
Akka简介以及入门案例
 

 可以看到这个Actor已经启动,其中/user/remoteActor是这个actor的访问路径

下面我们编写一个本地端Actor

import akka.actor.Actor
import akka.actor.ActorSystem
import akka.actor.Props
import com.typesafe.config.ConfigFactory
import java.io.File
import scala.concurrent.Await
import scala.concurrent.duration._
import akka.actor.ActorRef

object Local extends App {
  var akkaConf = ConfigFactory.parseString(
    s"""
      |akka.actor.provider = "akka.remote.RemoteActorRefProvider"
      |akka.remote.netty.tcp.transport-class = "akka.remote.transport.netty.NettyTransport"
      |akka.remote.netty.tcp.hostname = "127.0.0.1"
      |akka.remote.netty.tcp.port = 0
      """.stripMargin)
  val actorSystem = ActorSystem("local", akkaConf)
  val localActor1 = actorSystem.actorOf((Props(new LocalActor("localActor1"))), name = "LocalActor1") // the local actor
  val localActor2 = actorSystem.actorOf((Props(new LocalActor("localActor2"))), name = "LocalActor2") // the local actor
  val localActor3 = actorSystem.actorOf((Props(new LocalActor("localActor3"))), name = "LocalActor3") // the local actor
  val localActor4 = actorSystem.actorOf((Props(new LocalActor("localActor4"))), name = "LocalActor4") // the local actor
  localActor1 ! "START" // start the action
  localActor2 ! "START" // start the action
  localActor3 ! "START" // start the action
  localActor4 ! "START" // start the action

}
case object Tick
class LocalActor(name: String) extends Actor {
  // create the remote actor
  val remote = context.actorSelection("akka.tcp://[email protected]:5160/user/remoteActor")
  var counter = 0
  //var tiker = context.system.scheduler.schedule(1 millis, 100 millis)(println("hehheh"))
  def receive = {
    case "START" =>
      remote ! "Hello from the LocalActor:" + name

    case msg: String =>
      println(s"LocalActor received message: '$msg'")
      if (counter < 5) {
        sender ! "The " + counter + " message from the LocalActor:" + name
        counter += 1
      }
  }
}

 
 val remote = context.actorSelection("akka.tcp://[email protected]:5160/user/remoteActor")

就是连接远端的actor

我们启动local端,会看到连接信息

 
Akka简介以及入门案例
 


 

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