1.什么是Scala Actor
概念 Scala中的Actor能够实现并行编程的强大功能,它是基于事件模型的并发机制,Scala是运用消息(massage)的发送,接收来实现多线程的,使用Scala能够更能够地实现多线程应用的开发。
2.1传统java并发编程与Scala Actor编程的区别
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2.2 对于Java,它的多线程实现需要对共享资源(变量,对象等)使用synchronized关键字进行代码块同步,对象锁互斥等等,而且,常常一大块的try。。。catch语句块中加上wait方法,notify方法,notifyAll方法是让人很头疼的,原因在于Java中对数使用的是可变状态的对象资源,对这些资源进行共享来实现多线程编码的话,控制好资源竞争与防止对象状态被意外修改是非常重要的,而对象的不变性也是较难以保证的,而在Scala中,我们可以赋值不可变状态的资源(即对象,Scala中一切都是对象,连函数,方法也是)的一个副本,再基于Actor的消息发送,接收机制并行编程
2.3.Actor方法执行顺序
1.首先调用start()方法启动Actor
2.调用start()方法后其act()方法会被执行
3.向Actor发送消息
2.4.发送消息的方式
3. Actor实战 实例一
package practice
import scala.actors.Actor
object MyActor1 extends Actor{
override def act(): Unit = {
for (i<- 1 to 10){
println("actor" +i)
Thread.sleep(2000)
}
}
}
object MyActor2 extends Actor{
override def act(): Unit = {
for ( i <- 1 to 10 ){
println("actor-2" +i)
Thread.sleep(2000)
}
}
}
object ActotTest extends App{
MyActor1.start()
MyActor2.start()
说明:上面分别调用两个单例对象的start()方法,他们的act()方法会被执行,相同与在java中开启两个线程,线程的run() 方法会被执行
注意:这两个Actor是并行的执行的,act() 方法中的for循环执行完成后actor程序就退出了
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第二个实例(可以不断地接收消息)
package practice
//自己给自己发送消息
import scala.actors.Actor
class MyActor extends Actor{
override def act(): Unit = {
while (true){
receive{
case "start" =>{
println("starting.....")
Thread.sleep(5000)
println("started")
}
case "stop" =>{
println("stoping ....")
Thread.sleep(5000)
println("stopped")
}
}
}
}
}
object MyActor {
def main(args: Array[String]): Unit = {
val actor = new MyActor
actor.start()
actor ! "start"
actor ! "stop"
println("消息发送完成")
}
}
import scala.actors.Actor
class MyActor extends Actor{
override def act(): Unit = {
while (true){
receive{
case "start" =>{
println("starting.....")
Thread.sleep(5000)
println("started")
}
case "stop" =>{
println("stoping ....")
Thread.sleep(5000)
println("stopped")
}
}
}
}
}
object MyActor {
def main(args: Array[String]): Unit = {
val actor = new MyActor
actor.start()
actor ! "start"
actor ! "stop"
println("消息发送完成")
}
}
说明:在act()方法加入了while(true)循环,就可以不停的接收消息
注意:发送start消息和stop的消息是异步的,但是Actor接收到消息执行的过程是同步的按顺序执行
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3.3 第三个例子(react 方式会复用线程,比receive更高效)
package practice
import scala.actors.Actor
class YourActor extends Actor{
override def act(): Unit = {
loop{
react{
case "start" => {
println("starting ...")
Thread.sleep(5000)
println("started")
}
case "stop" => {
println("stopping ...")
Thread.sleep(8000)
println("stopped ...")
}
}
}
}
}
object YourActor {
def main(args: Array[String]) {
val actor = new YourActor
actor.start()
actor ! "start"
actor ! "stop"
println("消息发送完成!")
}
}
说明:react 如果要反复执行消息出来,react外层要用loop,不能用while
3.4 第四个例子(结合case class 发送消息)
package practice
import scala.actors.Actor
case class SyncMsg(id:Int,msg:String)
case class AsyncMsg(id:Int,msg:String)
case class ReplyMsg(id:Int,msg:String)
class AppleActor extends Actor{
override def act(): Unit = {
while (true){
receive{
case "start" => println("starting ....")
case SyncMsg(id,msg) =>{
println(id+",sync"+msg)
Thread.sleep(5000)
sender !ReplyMsg(3,"finished")
}
case AsyncMsg(id,msg) =>{
println(id +",astnc"+msg)
Thread.sleep(5000)
}
}
}
}
}
object AppleActor{
def main(args: Array[String]): Unit = {
val a=new AppleActor
a.start()
//异步消息
a ! AsyncMsg(1,"hello actor")
println("异步消息发送完成")
//同步消息
val reply= a !! SyncMsg(2 ,"hello actor")
println(reply.isSet)
val c=reply.apply()
println(reply.isSet)
println(c)
}
}