运行 Wicket 应用程序中并发一个计时器

Question

是否可以在 wicket 应用程序中并发运行计时器线程？下面是我正在尝试做的示例代码。收到一条消息后，我想添加一些延迟，所以我运行ning 了一个计时器，但是当我启动计时器时，主线程停止了，并且在计时器运行ning 的持续时间内我没有收到任何消息其他消息。运行计时器是否可以与主线程并行？谢谢

public class Test extends WebPage{
    private Queue<String> msgQueue;
    Test(){
        msgQueue = new ConcurrentLinkedQueue<String>();
        add( new WebSocketBehavior() {      

        @Override
        protected void onMessage(WebSocketRequestHandler handler,
                    TextMessage message) {
            super.onMessage(handler, message);
            handleMessage(handler,message);
        }

    private void handleMessage(WebSocketRequestHandler handler, TextMessage msg){
        msgQueue.add(msg.getText());
        Timer timer = new Timer();
        Application application = getApplication();
        timer.schedule( new TimerTask() {
            @Override
            public void run() {
                if (!Application.exists()) {
                    ThreadContext.setApplication(application);
                }
                System.out.println(getApplication());
            }
        }, 5000);
    }
}´

我收到 java.io.NotSerializableException 异常，如以下使用 ScheduledThreadPoolExecutor 的日志所示：

    Nov 27, 2016 8:19:10 PM org.apache.wicket.serialize.java.JavaSerializer serialize
    SEVERE: Error serializing object class Test [object=[Page class = Test, id = 0, render count = 1]]
    org.apache.wicket.core.util.objects.checker.CheckingObjectOutputStream$ObjectCheckException: The object type is not Serializable!
    A problem occurred while checking object with type: java.util.concurrent.ScheduledThreadPoolExecutor

        private final java.util.concurrent.ScheduledExecutorService Test.scheduler [class=java.util.concurrent.ScheduledThreadPoolExecutor] <----- field that is causing the problem
        at org.apache.wicket.core.util.objects.checker.CheckingObjectOutputStream.internalCheck(CheckingObjectOutputStream.java:362)
        at org.apache.wicket.core.util.objects.checker.CheckingObjectOutputStream.check(CheckingObjectOutputStream.java:341)
        at org.apache.wicket.core.util.objects.checker.CheckingObjectOutputStream.checkFields(CheckingObjectOutputStream.java:605)
        at org.apache.wicket.core.util.objects.checker.CheckingObjectOutputStream.internalCheck(CheckingObjectOutputStream.java:541)
        at org.apache.wicket.core.util.objects.checker.CheckingObjectOutputStream.check(CheckingObjectOutputStream.java:341)
        at org.apache.wicket.core.util.objects.checker.CheckingObjectOutputStream.writeObjectOverride(CheckingObjectOutputStream.java:673)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:344)
        at org.apache.wicket.serialize.java.JavaSerializer$SerializationCheckerObjectOutputStream.writeObjectOverride(JavaSerializer.java:267)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:344)
        at org.apache.wicket.serialize.java.JavaSerializer.serialize(JavaSerializer.java:78)
        at org.apache.wicket.pageStore.AbstractPageStore.serializePage(AbstractPageStore.java:133)
        at org.apache.wicket.pageStore.DefaultPageStore.createSerializedPage(DefaultPageStore.java:281)
        at org.apache.wicket.pageStore.DefaultPageStore.storePage(DefaultPageStore.java:61)
        at org.apache.wicket.page.PageStoreManager$PersistentRequestAdapter.storeTouchedPages(PageStoreManager.java:403)
        at org.apache.wicket.page.RequestAdapter.commitRequest(RequestAdapter.java:193)
        at org.apache.wicket.page.AbstractPageManager.commitRequest(AbstractPageManager.java:76)
        at org.apache.wicket.page.PageManagerDecorator.commitRequest(PageManagerDecorator.java:74)
        at org.apache.wicket.page.PageAccessSynchronizer.commitRequest(PageAccessSynchronizer.java:270)
        at org.apache.wicket.protocol.ws.api.AbstractWebSocketProcessor.onDetach(AbstractWebSocketProcessor.java:297)
        at org.apache.wicket.request.cycle.RequestCycleListenerCollection.notify(RequestCycleListenerCollection.java:105)
        at org.apache.wicket.request.cycle.RequestCycleListenerCollection.notify(RequestCycleListenerCollection.java:101)
        at org.apache.wicket.util.listener.ListenerCollection.notify(ListenerCollection.java:120)
        at org.apache.wicket.util.listener.ListenerCollection.reversedNotify(ListenerCollection.java:144)
        at org.apache.wicket.util.listener.ListenerCollection.reversedNotifyIgnoringExceptions(ListenerCollection.java:113)
        at org.apache.wicket.request.cycle.RequestCycleListenerCollection.onDetach(RequestCycleListenerCollection.java:100)
        at org.apache.wicket.request.cycle.RequestCycle.onDetach(RequestCycle.java:649)
        at org.apache.wicket.request.cycle.RequestCycle.detach(RequestCycle.java:594)
        at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:297)
        at org.apache.wicket.protocol.ws.api.AbstractWebSocketProcessor.broadcastMessage(AbstractWebSocketProcessor.java:257)
        at org.apache.wicket.protocol.ws.api.AbstractWebSocketProcessor.onConnect(AbstractWebSocketProcessor.java:175)
        at org.apache.wicket.protocol.ws.javax.JavaxWebSocketProcessor.<init>(JavaxWebSocketProcessor.java:48)
        at org.apache.wicket.protocol.ws.javax.WicketEndpoint.onOpen(WicketEndpoint.java:58)
        at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.init(WsHttpUpgradeHandler.java:129)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:629)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
    Caused by: java.io.NotSerializableException: java.util.concurrent.ScheduledThreadPoolExecutor
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
        at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
        at org.apache.wicket.serialize.java.JavaSerializer$SerializationCheckerObjectOutputStream.writeObjectOverride(JavaSerializer.java:256)

Answer 1

您可以将 ScheduledExecutorService 用于调度程序任务（在单独的线程中运行），如下面的内联注释所示：

public class Test extends WebPage{

  //Initialise ScheduledExecutorService thread pool
  private final ScheduledExecutorService scheduler =
                 Executors.newScheduledThreadPool(1);

    private Queue<String> msgQueue;
        Test(){
            msgQueue = new ConcurrentLinkedQueue<String>();
            add( new WebSocketBehavior() {      

            @Override
            protected void onMessage(WebSocketRequestHandler handler,
                        TextMessage message) {
                super.onMessage(handler, message);
                handleMessage(handler,message);
            }

        private void handleMessage(WebSocketRequestHandler handler,
                                                    TextMessage msg){
            msgQueue.add(msg.getText());
            Timer timer = new Timer();
            final Application application = getApplication();

            //Implement Runnable which runs in sep. Thread
            Runnable runnable = () -> {
                if (!Application.exists()) {
                    ThreadContext.setApplication(application);
                }
            };

            //Start the scheduler Now which runs for every 5 seconds
            ScheduledFuture<V> timer = scheduler.schedule(runnable, 5000, TimeUnit.SECONDS);
            //you can check timer.isDone()
        }
    }

    private static void enhancedLoop(int[] numbers) {
        //add your code
    }

您可以查看 here 以了解有关 ScheduledExecutorService 的更多信息。

Answer 2

TL;DR：将调度程序移至 YourApplication.java 并公开 API 以安排任务。无论如何，每个页面都不需要调度程序。

更多详细信息请阅读这篇文章：参见 http://wicketinaction.com/2014/07/working-with-background-jobs/

运行 Wicket 应用程序中并发一个计时器

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