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.