在Wicket應用程序中同時運行計時器

Question

是否可以在檢票應用程序中同時運行計時器線程？ 下面是我想要做的示例代碼。 在收到消息時，我想添加一些延遲，所以我正在運行一個計時器，但是當啓動計時器時，主線程停止運行，並且在計時器運行期間，我沒有收到任何其他消息。 是否有可能與主線程並行運行定時器？謝謝。

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); 
    } 
}´ 

我得到java.io.NotSerializableException例外，因爲可以在下面的日誌中可以看出使用的ScheduledThreadPoolExecutor：

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$2.commitRequest(PageAccessSynchronizer.java:270) 
     at org.apache.wicket.protocol.ws.api.AbstractWebSocketProcessor$1.onDetach(AbstractWebSocketProcessor.java:297) 
     at org.apache.wicket.request.cycle.RequestCycleListenerCollection$3.notify(RequestCycleListenerCollection.java:105) 
     at org.apache.wicket.request.cycle.RequestCycleListenerCollection$3.notify(RequestCycleListenerCollection.java:101) 
     at org.apache.wicket.util.listener.ListenerCollection$1.notify(ListenerCollection.java:120) 
     at org.apache.wicket.util.listener.ListenerCollection.reversedNotify(ListenerCollection.java:144) 
     at org.apache.wicket.util.listener.ListenerCollection.reversedNotifyIgnoringExceptions(ListenerCollection.java:113) 
     at org.apache.wicket.request.cycle.RequestCycleListenerCollection.onDetach(RequestCycleListenerCollection.java:100) 
     at org.apache.wicket.request.cycle.RequestCycle.onDetach(RequestCycle.java:649) 
     at org.apache.wicket.request.cycle.RequestCycle.detach(RequestCycle.java:594) 
     at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:297) 
     at org.apache.wicket.protocol.ws.api.AbstractWebSocketProcessor.broadcastMessage(AbstractWebSocketProcessor.java:257) 
     at org.apache.wicket.protocol.ws.api.AbstractWebSocketProcessor.onConnect(AbstractWebSocketProcessor.java:175) 
     at org.apache.wicket.protocol.ws.javax.JavaxWebSocketProcessor.<init>(JavaxWebSocketProcessor.java:48) 
     at org.apache.wicket.protocol.ws.javax.WicketEndpoint.onOpen(WicketEndpoint.java:58) 
     at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.init(WsHttpUpgradeHandler.java:129) 
     at org.apache.coyote.AbstractProtocol$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

TL; DR：將調度程序移入YourApplication.java並公開API以調度任務。無論如何，每頁不需要調度程序。

如需更詳細的信息，請閱讀這篇文章： 見http://wicketinaction.com/2014/07/working-with-background-jobs/

Answer 2

可以使用ScheduledExecutorService的調度任務（運行在單獨的線程），如圖所示在下面內嵌批註：

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 
    } 

你可以看看here爲了解更多關於ScheduledExecutorService。