import akka.actor.DeadLetter; //导入依赖的package包/类
@Override
   public void onReceive(Object message) {
if (message instanceof DeadLetter) {
    Object innerMessage = ((DeadLetter) message).message();
    logger.warn(".onReceive: encountered dead letter: {}", innerMessage);
       if (innerMessage instanceof RegisterWorker){
           logger.error("worker could not register to supervisor, shutting down");
           BatchApplication.exit();
       }
}
   }
 

import akka.actor.DeadLetter; //导入依赖的package包/类
@Override
public Receive createReceive() {
    return ReceiveBuilder.create().match(DeadLetter.class, msg -> {
        System.out.println(msg);
    }).matchAny(msg -> {
        System.out.println(msg);
    }).build();
}
 

import akka.actor.DeadLetter; //导入依赖的package包/类
@SuppressWarnings({ "rawtypes", "unchecked" })
@Test
public void testDataChangedWithNoSender() {
    new JavaTestKit(getSystem()) {
        {
            final AsyncDataChangeEvent mockChangeEvent = Mockito.mock(AsyncDataChangeEvent.class);
            final AsyncDataChangeListener mockListener = Mockito.mock(AsyncDataChangeListener.class);
            final Props props = DataChangeListener.props(mockListener, TEST_PATH);
            final ActorRef subject = getSystem().actorOf(props, "testDataChangedWithNoSender");

            getSystem().eventStream().subscribe(getRef(), DeadLetter.class);

            subject.tell(new DataChanged(mockChangeEvent), ActorRef.noSender());

            // Make sure no DataChangedReply is sent to DeadLetters.
            while (true) {
                DeadLetter deadLetter;
                try {
                    deadLetter = expectMsgClass(duration("1 seconds"), DeadLetter.class);
                } catch (AssertionError e) {
                    // Timed out - got no DeadLetter - this is good
                    break;
                }

                // We may get DeadLetters for other messages we don't care
                // about.
                Assert.assertFalse("Unexpected DataChangedReply", deadLetter.message() instanceof DataChangedReply);
            }
        }
    };
}
 

import akka.actor.DeadLetter; //导入依赖的package包/类
@Test
public void testDataChangedWithNoSender() {
    new JavaTestKit(getSystem()) {
        {
            final DataTreeCandidate mockTreeCandidate = Mockito.mock(DataTreeCandidate.class);
            final ImmutableList<DataTreeCandidate> mockCandidates = ImmutableList.of(mockTreeCandidate);
            final DOMDataTreeChangeListener mockListener = Mockito.mock(DOMDataTreeChangeListener.class);
            final Props props = DataTreeChangeListenerActor.props(mockListener, TEST_PATH);
            final ActorRef subject = getSystem().actorOf(props, "testDataTreeChangedWithNoSender");

            getSystem().eventStream().subscribe(getRef(), DeadLetter.class);

            subject.tell(new DataTreeChanged(mockCandidates), ActorRef.noSender());

            // Make sure no DataChangedReply is sent to DeadLetters.
            while (true) {
                DeadLetter deadLetter;
                try {
                    deadLetter = expectMsgClass(duration("1 seconds"), DeadLetter.class);
                } catch (AssertionError e) {
                    // Timed out - got no DeadLetter - this is good
                    break;
                }

                // We may get DeadLetters for other messages we don't care
                // about.
                Assert.assertFalse("Unexpected DataTreeChangedReply",
                        deadLetter.message() instanceof DataTreeChangedReply);
            }
        }
    };
}
 

import akka.actor.DeadLetter; //导入依赖的package包/类
@Test
public void shouldSendMsgToDeadLetterWhenQueueIsFull() throws InterruptedException {
    final JavaTestKit mockReceiver = new JavaTestKit(actorSystem);
    actorSystem.eventStream().subscribe(mockReceiver.getRef(), DeadLetter.class);

    final FiniteDuration twentySeconds = new FiniteDuration(20, TimeUnit.SECONDS);

    ActorRef pingPongActor = actorSystem.actorOf(PingPongActor.props(lock).withMailbox(config.getMailBoxName()),
                                                 "pingpongactor");

    actorSystem.mailboxes().settings();
    lock.lock();
    try {
        //queue capacity = 10
        //need to send 12 messages; 1 message is dequeued and actor waits on lock,
        //2nd to 11th messages are put on the queue
        //12th message is sent to dead letter.
        for (int i = 0; i < 12; i++) {
            pingPongActor.tell("ping", mockReceiver.getRef());
        }

        mockReceiver.expectMsgClass(twentySeconds, DeadLetter.class);
    } finally {
        lock.unlock();
    }

    mockReceiver.receiveN(11, twentySeconds);
}
 

import akka.actor.DeadLetter; //导入依赖的package包/类
public DeadLetterActor() {
    receive(ReceiveBuilder.match(DeadLetter.class, msg -> {
        LOGGER.warn("Following message fail to be distributed from {} to {} : {}", msg.sender().path(), msg.recipient().path(), msg.message().toString());
    }).build());
}
 

import akka.actor.DeadLetter; //导入依赖的package包/类
@Override
public void onReceive(Object message) throws Exception {
    if (message instanceof DeadLetter) {
        DeadLetter deadLetter = (DeadLetter) message;
        writeDeadLetterToFile(deadLetter);
    } else {
        String className = message != null ? message.getClass().getName() : "NULL";
        String value = message != null ? message.toString() : "NULL";
        log.error(String.format("Message sent to DeadLetter but it is not one (Class: %s, Value: %s)", className, value));
    }
}
 

import akka.actor.DeadLetter; //导入依赖的package包/类
/**
 * Write the dead letters to the file system
 * 
 * @param deadLetter
 *            a dead letter
 */
private void writeDeadLetterToFile(DeadLetter deadLetter) {
    String fileName = String.format(OUTPUT_FILE_NAME_TEMPLATE, deadLetter.recipient().path().name(), new Date(), ".log");
    BufferedWriter bWriter = null;
    try {
        bWriter = new BufferedWriter(new FileWriter(new File(getDeadLetterFileSystem(), fileName)));
        // Serialize the message as XML
        ByteArrayOutputStream baOut = new ByteArrayOutputStream();
        XMLEncoder encoder = new XMLEncoder(baOut);
        if (deadLetter.message() != null) {
            encoder.writeObject(deadLetter.message());
        }
        encoder.flush();
        encoder.close();
        // Write it to a file
        // First line is actor path
        bWriter.write(deadLetter.recipient().path().toString());
        bWriter.newLine();
        // Then write the message
        bWriter.write(baOut.toString());
        bWriter.flush();
    } catch (Exception e) {
        log.error("Error while writing the dead letter info the dead letters folder", e);
    } finally {
        IOUtils.closeQuietly(bWriter);
    }
}
 

import akka.actor.DeadLetter; //导入依赖的package包/类
/**
 * Initialize the dead letter actor (which is actually this class)
 * 
 * @throws ActorSystemPluginException
 */
private void initializeTheDeadLetterActor(final File deadLetterFileSystem, final File reprocessedDeadLetters) throws ActorSystemPluginException {
    final ActorRef actor = getActorSystem().actorOf(Props.create(new DeadLetterManager.DeadLetterCreator(deadLetterFileSystem, reprocessedDeadLetters)));
    getActorSystem().eventStream().subscribe(actor, DeadLetter.class);
}