标签：who 笔记 调用 new err 发送消息 dap adapter gets
官方文档: http://developer.lightbend.com/guides/akka-quickstart-java/?_ga=2.177525157.1012573474.1504767665-546319647.1504766934
一. AKKA Hello World example :
1.首先需要创建一个ActorSystem, 它是所有Actor运行的容器.
2.其次创建Greeter Actor和Printer Actor.
3.发送消息到Greeter Actor实例, 它们会先在内部存储消息.
4.最后Greeter Actor里面的指令消息会触发它们发送消息给Printer Actor, 然后Printer Actor会执行对应的操作.
二. 定义Actors和messages
messages可以是任意类型(any subtype of Object).
当定义Actors和它们的messages时, 要遵守以下规范:
1.因为messages是Actor的公共API, 所以给messages定义名称的时候要富含语义以及特定领域的意义.
2.messages是不可变的, 因为它们在不同的线程之间共享.
3.把Actor相关的messages作为静态内部类放到Actor类中, 这样更容易理解actor需要处理什么类型的消息.
4.在Actor类中, 使用静态方法props描述如何构造Actor.
1 package com.lightbend.akka.sample; 2 3 import akka.actor.AbstractActor; 4 import akka.actor.ActorRef; 5 import akka.actor.Props; 6 import com.lightbend.akka.sample.Printer.Greeting; 7 8 public class Greeter extends AbstractActor { 9 static public Props props(String message, ActorRef printerActor) { 10 return Props.create(Greeter.class, () -> new Greeter(message, printerActor)); 11 } 12 13 static public class WhoToGreet { 14 public final String who; 15 16 public WhoToGreet(String who) { 17 this.who = who; 18 } 19 } 20 21 static public class Greet { 22 public Greet() { 23 } 24 } 25 26 private final String message; 27 private final ActorRef printerActor; 28 private String greeting = ""; 29 30 public Greeter(String message, ActorRef printerActor) { 31 this.message = message; 32 this.printerActor = printerActor; 33 } 34 35 @Override 36 public Receive createReceive() { 37 return receiveBuilder() 38 .match(WhoToGreet.class, wtg -> { 39 this.greeting = message + ", " + wtg.who; 40 }) 41 .match(Greet.class, x -> { 42 printerActor.tell(new Greeting(greeting), getSelf()); 43 }) 44 .build(); 45 } 46 }
1 package com.lightbend.akka.sample; 2 3 import akka.actor.AbstractActor; 4 import akka.actor.ActorRef; 5 import akka.actor.Props; 6 import akka.event.Logging; 7 import akka.event.LoggingAdapter; 8 9 public class Printer extends AbstractActor { 10 static public Props props() { 11 return Props.create(Printer.class, () -> new Printer()); 12 } 13 14 static public class Greeting { 15 public final String message; 16 17 public Greeting(String message) { 18 this.message = message; 19 } 20 } 21 22 private LoggingAdapter log = Logging.getLogger(getContext().getSystem(), this); 23 24 public Printer() { 25 } 26 27 @Override 28 public Receive createReceive() { 29 return receiveBuilder() 30 .match(Greeting.class, greeting -> { 31 log.info(greeting.message); 32 }) 33 .build(); 34 } 35 }
三.创建Actor对象
Actor不能用过new来创建, 而是通过工厂来创建Actor对象, 工厂返回的不是actor实例, 而是一个引用akka.actor.ActorRef, 这个引用指向actor实例.
akka.actor.ActorSystem类似于Spring的BeanFactory. 它作为Actor的容器, 管理actor的生命周期. 工厂方法actorOf通过两个参数创建Actor对象, 一个参数是配置对象Props, 一个参数是actor的名称.
1 final ActorRef printerActor = 2 system.actorOf(Printer.props(), "printerActor"); 3 final ActorRef howdyGreeter = 4 system.actorOf(Greeter.props("Howdy", printerActor), "howdyGreeter"); 5 final ActorRef helloGreeter = 6 system.actorOf(Greeter.props("Hello", printerActor), "helloGreeter"); 7 final ActorRef goodDayGreeter = 8 system.actorOf(Greeter.props("Good day", printerActor), "goodDayGreeter");
四. 异步通信
Actor是响应式的和消息驱动的. 一个Actor不会做任何事情知道它接收到一个消息.Actors通过异步消息来通信. 这确保了消息的发送者(sender)不用停下来等待它们的消息被接受者(recipient)处理. 相反的, 发送者只要把消息放到接收者的邮筒(mailbox)里后就可以去干别的事了. 而这个邮筒本子上是一个有序的消息队列. 来自同一个Actor的多条消息是有序的, 而来自不同的Actor的消息是交错的.
当actor不处理消息的时候是处于一个暂停的状态, 此时它不消耗除内存以外的任何资源.
五. 发送消息到Actor
把消息放到Actor的邮筒(mailbox)里, 需要调用ActorRef的tell方法. 举个栗子:
把消息发送给Greeter Actor :
1 howdyGreeter.tell(new WhoToGreet("Akka"), ActorRef.noSender()); 2 howdyGreeter.tell(new Greet(), ActorRef.noSender()); 3 4 howdyGreeter.tell(new WhoToGreet("Lightbend"), ActorRef.noSender()); 5 howdyGreeter.tell(new Greet(), ActorRef.noSender()); 6 7 helloGreeter.tell(new WhoToGreet("Java"), ActorRef.noSender()); 8 helloGreeter.tell(new Greet(), ActorRef.noSender()); 9 10 goodDayGreeter.tell(new WhoToGreet("Play"), ActorRef.noSender()); 11 goodDayGreeter.tell(new Greet(), ActorRef.noSender());
Greeter Actor给Printer Actor发送消息:
printerActor.tell(new Greeting(greeting), getSelf());
标签：who 笔记 调用 new err 发送消息 dap adapter gets
原文地址：http://www.cnblogs.com/CoolJayson/p/7490946.html
