通过Typesafe Activator创建akka java sample
通过Typesafe Activator创建akka java sample
What is Typesafe Activator?
Typesafe Activator gets you started with the Typesafe Reactive Platform, including Akka, Play Framework and Scala. It is a hub for developers that want to build reactive applications, providing an in browser environment for creating new applications.
首先安装Typesafe Activator，然后启动它，如下所示，找到该模板，创建项目，
根据这个例子，为了简单，做了一些修改。
实现HelloWorld的actor，这个actor的作用就是发出问候消息，并且接收MSG.DONE的消息，处理之，如下，
package sample.hello;
import akka.actor.Props;
import akka.actor.UntypedActor;
import akka.actor.ActorRef;
public class HelloWorld extends UntypedActor {
/**
* Is called when an Actor is started.
*/
@Override
public void preStart() {
// create the greeter actor
final ActorRef greeter = getContext().actorOf(Props.create(Greeter.class), "greeter");
// 把Greeter.Msg.GREET这个消息发送给给名字为greeter的actor，发送者是self
//getSelf() 是一个sender
greeter.tell(Greeter.Msg.GREET, getSelf());
}
@Override
public void onReceive(Object msg) {
if (msg == Greeter.Msg.DONE) {
// when the greeter is done, stop this actor and with it the application
getContext().stop(getSelf());
} else
unhandled(msg);
}
}
然后相应的Greeter的actor接收问候消息，然后打印，然后向其消息的发送者发送DONE的消息，如下，
package sample.hello;
import akka.actor.UntypedActor;
public class Greeter extends UntypedActor {
public static enum Msg {
GREET, DONE;
}
@Override
public void onReceive(Object msg) {
if (msg == Msg.GREET) {
//得到Msg.GREET消息，打印
System.out.println("Hello World!");
// 得到当前消息的发送者，并告诉这个发送者消息应经处理完成，
// 此时Msg.DONE的发送者是self
getSender().tell(Msg.DONE, getSelf());
} else
unhandled(msg);
}
}
这是两个actor的交互行为，在引入第三个actor，负责监视HelloWorld的actor，当其发出Terminated的消息时，这个负责监视的actor会处理之，
如下，
package sample.hello;
import akka.actor.ActorRef;
import akka.actor.Terminated;
import akka.actor.UntypedActor;
import akka.event.Logging;
import akka.event.LoggingAdapter;
public class Terminator extends UntypedActor {
private final LoggingAdapter log = Logging.getLogger(getContext().system(), this);
private final ActorRef ref;
/**
* 此时的Terminator actor要观察另一个actor ref
*
* @param ref
*/
public Terminator(ActorRef ref) {
this.ref = ref;
//Registers this actor as a Monitor-监视 for the provided ActorRef.
getContext().watch(ref);
}
@Override
public void onReceive(Object msg) {
if (msg instanceof Terminated) {
log.info("||||||||{} has terminated, shutting down system", ref.path());
getContext().system().shutdown();
} else {
unhandled(msg);
}
}
}
下面就是启动类，如下，
package sample.hello;
import akka.actor.ActorRef;
import akka.actor.ActorSystem;
import akka.actor.Props;
public class Main2 {
public static void main(String[] args) {
ActorSystem system = ActorSystem.create("Hello");
//actorOf--Create new actor as child of this context with the given name
//actor 的名字是helloWorld
/**
* 当创建helloWorld的actor时，会通过preStart创建一个greeter的actor，
* 然后greeter.tell(Greeter.Msg.GREET, getSelf());
*/
ActorRef a = system.actorOf(Props.create(HelloWorld.class), "helloWorld");
//actorOf--Create new actor as child of this context with the given name
//actor 的名字是terminator
system.actorOf(Props.create(Terminator.class, a), "terminator");
}
}
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