知识库--Sending and Receiving Messages By Akka Using Java(139)

1 Creating Actors

2 Sending and Receiving Messages

3 Working with Multiple Actors

4 Coordinating Actors

5 Using Typed Actors

6 Typed Actors and Murmurs

7 Mixing Actors and STM

8 Using Transactors

9 Coordinating Typed Actors

10 Remote Actors

11 Limitations of the Actor-Based Model

12 epliogue

replyUnsafe（）method 回应消息，不检查发送者

import akka.actor.UntypedActor;
import akka.actor.ActorRef;
import akka.actor.Actors;
import akka.actor.ActorTimeoutException;

public class FortuneTeller extends UntypedActor {
public void onReceive(final Object name) {
getContext().replyUnsafe(String.format("%s you'll rock", name));
}

public static void main(final String[] args) {
final ActorRef fortuneTeller =
Actors.actorOf(FortuneTeller.class).start();
try {
final Object response = fortuneTeller.sendRequestReply("Joe");
System.out.println(response);
} catch(ActorTimeoutException ex) {
System.out.println("Never got a response before timeout");
} finally {
fortuneTeller.stop();
}
}
}

结果

Joe you'll rock

replySafe（）method 回应消息，检查发送者

import akka.actor.UntypedActor;
import akka.actor.Actors;
import akka.actor.ActorRef;
import akka.actor.ActorTimeoutException;

public class FortuneTeller extends UntypedActor {
public void onReceive(final Object name) {
if(getContext().replySafe(String.format("%s you'll rock", name)))
System.out.println("Message sent for " + name);
else
System.out.println("Sender not found for " + name);
}

public static void main(final String[] args) {
final ActorRef fortuneTeller =
Actors.actorOf(FortuneTeller.class).start();

try {
fortuneTeller.sendOneWay("Bill");
final Object response = fortuneTeller.sendRequestReply("Joe");
System.out.println(response);
} catch(ActorTimeoutException ex) {
System.out.println("Never got a response before timeout");
} finally {
fortuneTeller.stop();
}
}
}

结果

Sender not found for Bill
Message sent for Joe
Joe you'll rock

分析

The call to sendRequestReply() blocks while waiting for a response, but the call to sendOneWay() is nonblocking and yields no response. If we want to receive a response but don’t want to wait for it, we can use the more elaborate method sendRequestReplyFuture(), which will return a Future object. We can go

about doing work until we want the response, at which time we can either block or query the future object to see whether a response is available. Similarly, on the side of the actor, we can get the senderFuture from the context reference and communicate through that right away or later when we have a response ready.

It is quite convenient that Akka passes the sender references under the covers when it sends a message. This eliminates the need to pass the sender explicitly as part of the message and removes so much noise and effort in the code.