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 BillMessage sent for JoeJoe 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.