目录
0、Acotr
(1)java 和 scala 的关联:
Scala的Actor类似于Java中的多线程编程
(2)java 和 scala 的区别:
1>Scala的Actor尽可能地避免锁和共享状态,从而避免多线程并发时出现资源争用的情况,进而提升多线程编程的性能
2>Scala Actor的这种模型还可以避免死锁等一系列传统多线程编程的问题
(3)Spark中使用的分布式多线程框架:Akka
1、Actor的创建、启动和消息收发
(1)结构:
1>声明结构:
class xxActor extends Actor {
def act() {
while (true) {
receive {
case name:String => 功能代码
}
}
}
}
2>调用结构:
xxActor.start()
xxActor ! var
例子:
import scala.actors.Actor
class HelloActor extends Actor {
def act() {
while (true) {
receive {
case name: String => println("Hello, " + name)
}
}
}
}
val helloActor = new HelloActor
helloActor.start()
helloActor ! "leo"
(2)特点:
actor内部使用receive和模式匹配接收消息
使用!符号,向actor发送消息
2、收发case class类型的消息
(1)特点:匹配一个Class(更加饱满的进行消息传递)
case class来作为消息进行发送
例子:
case class Login(username: String, password: String)
case class Register(username: String, password: String)
class UserManageActor extends Actor {
def act() {
while (true) {
receive {
case Login(username, password) => println("login, username is " + username + ", password is " + password)
case Register(username, password) => println("register, username is " + username + ", password is " + password)
}
}
}
}
val userManageActor = new UserManageActor
userManageActor.start()
userManageActor ! Register("leo", "1234"); userManageActor ! Login("leo", "1234")
3、Actor之间互相收发消息
互发消息的思路:
传递参数,新增一个Actor传入,在功能代码中进行调用即可!!
例子: 打电话
case class Message(content: String, sender: Actor)
class LeoTelephoneActor extends Actor {
def act() {
while (true) {
receive {
case Message(content, sender) => { println("leo telephone: " + content); sender ! "I'm leo, please call me after 10 minutes." }
}
}
}
}
class JackTelephoneActor(val leoTelephoneActor: Actor) extends Actor {
def act() {
leoTelephoneActor ! Message("Hello, Leo, I'm Jack.", this)
receive {
case response: String => println("jack telephone: " + response)
}
}
}
为何建议使用 "case class" , 普通类是否可行?
举例:
假如以上的Message创建替换为:
class Message(content: String, sender: Actor)
结果:则在case 匹配语句中,无法检测到 可匹配的Message类
结论:使用 case class 类来配合使用 “case” 语句
4、同步消息和Future(例子待合适情景验证)
(1)同步:
方式:即对方接受后,一定要给自己返回结果,那么可以使用!?的方式发送消息
结构:val reply = actor !? message
例子:
import scala.actors.Actor
class HelloActor extends Actor {
def act() {
while (true) {
receive {
case name: String => "Hello, " + name
}
}
}
}
val helloActor = new HelloActor
helloActor.start()
val reply = helloActor !? "leo"
(2)异步
默认异步:之前的 "actor ! message " 的发送方式
后续主动获取返回值:
val future = actor !! message;
val reply = future()
例子:
import scala.actors.Actor
class HelloActor extends Actor {
def act() {
while (true) {
receive {
case name: String => "Hello, " + name
}
}
}
}
val helloActor = new HelloActor
helloActor.start()
val future = helloActor !! "leo"
val reply = future()