Package org.zkoss.zk.ui.impl

Class PollingServerPush

  • All Implemented Interfaces:
    ServerPush
    public class PollingServerPush
extends java.lang.Object
implements ServerPush
    A server-push implementation that is based on client-polling.

    Developer can control the frequency of the polling by setting the preferences as follows:

    PollingServerPush.delay.min
    The minimal delay to send the second polling request (unit: milliseconds). Default: 1000.
    PollingServerPush.delay.max
    The maximal delay to send the second polling request (unit: milliseconds). Default: 15000.
    PollingServerPush.delay.factor
    the delay factor. The real delay is the processing time multiplies the delay factor. For example, if the last request took 1 second to process, then the client polling will be delayed for 1 x factor seconds. Default: 5. The larger the factor is, the longer delay it tends to be.

    Another way to control the frequency is to instantiate an instance with PollingServerPush(int, int, int), and then assign it with DesktopCtrl.enableServerPush(ServerPush). 

    desktop.enableServerPush(new PollingServerPush(1000, 5000, -1));
    Since:
    5.0.0
    Author:
    tomyeh

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean activate​(long timeout)
      Activate the current thread (which must be a server-push thread).
      boolean deactivate​(boolean stop)
      Deactivates the current thread (which must be a server-push thread).
      protected java.lang.String getStartScript()
      Returns the JavaScript codes to enable (a.k.a., start) the server push.
      protected java.lang.String getStopScript()
      Returns the JavaScript codes to disable (a.k.a., stop) the server push.
      boolean isActive()
      Returns if the working thread of the server push is active.
      void onPiggyback()
      Called when Events.ON_PIGGYBACK is received.
      void resume()
      ZK-1777 resume serverpush after DesktopRecycling
      <T extends Event>
      void      		 schedule​(EventListener<T> listener, T event, Scheduler<T> scheduler)
      Called by the associated desktop to schedule a task to execute asynchronously.
      void start​(Desktop desktop)
      Starts and initializes the server-push controller.
      protected void startClientPush()
      Sends an AU response to the client to start the server push.
      void stop()
      Stops and cleans up the server-push controller.
      protected void stopClientPush()
      Sends an AU response the client to stop the server push.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • PollingServerPush

        public PollingServerPush()

      • PollingServerPush

        public PollingServerPush​(int min,
                         int max,
                         int factor)
        Parameters:
        min - the minimal delay before sending the second polling request (unit: milliseconds). If negative, the default is used (see PollingServerPush).
        max - the maximal delay before sending the second polling request (unit: milliseconds). If negative, the default is used (see PollingServerPush).
        factor - the delay factor. If negative, the default is used (see PollingServerPush).
        Since:
        5.0.4

    • Method Detail

      • startClientPush

        protected void startClientPush()
        Sends an AU response to the client to start the server push. It is called by start(org.zkoss.zk.ui.Desktop).

        The derived class usually overrides this method to support different devices, such as ZK Mobile.

        The default implementation is to send AuScript containing the script returned by getStartScript(). Devices that don't support scripts could override this method to send a custom AU response (AuResponse).

      • stopClientPush

        protected void stopClientPush()
        Sends an AU response the client to stop the server push.

        The derived class usually overrides this method to support different devices, such as ZK Mobile.

        The default implementation is to send AuScript containing the script returned by getStopScript(). Devices that don't support scripts could override this method to send a custom AU response (AuResponse).

      • getStartScript

        protected java.lang.String getStartScript()
        Returns the JavaScript codes to enable (a.k.a., start) the server push. It is called by startClientPush() to prepare the script of AuScript that will be sent to the client.

      • getStopScript

        protected java.lang.String getStopScript()
        Returns the JavaScript codes to disable (a.k.a., stop) the server push. It is called by stopClientPush() to prepare the script of AuScript that will be sent to the client.

      • resume

        public void resume()
        ZK-1777 resume serverpush after DesktopRecycling
        Specified by:
        resume in interface ServerPush

      • onPiggyback

        public void onPiggyback()
        Description copied from interface: ServerPush
        Called when Events.ON_PIGGYBACK is received. The invocation is passive (i.e., triggered by other events, rather than spontaneous).

        This method is called in the context of an event listener. In other words, the execution is activated and you can retrieve it by Executions.getCurrent().

        Specified by:
        onPiggyback in interface ServerPush

      • schedule

        public <T extends Event> void schedule​(EventListener<T> listener,
                                       T event,
                                       Scheduler<T> scheduler)
        Description copied from interface: ServerPush
        Called by the associated desktop to schedule a task to execute asynchronously.

        The implementation usually delegates the scheduling to the scheduler passed as the third argument, which is controlled by the desktop. Of course, it could schedule it by itself.

        Specified by:
        schedule in interface ServerPush
        Parameters:
        listener - the task to execute
        event - the event to be passed to the task (i.e., the event listener). It could null or any instance as long as the task recognizes it.
        scheduler - the default scheduler to schedule the task. The implementation usually delegates the scheduling back to it. If you prefer to handle it by yourself, you could ignore it.

      • activate

        public boolean activate​(long timeout)
                 throws java.lang.InterruptedException,
                        DesktopUnavailableException
        Description copied from interface: ServerPush
        Activate the current thread (which must be a server-push thread). It causes the current thread to wait until the desktop is available to access, the desktop no longer exists, some other thread interrupts this thread, or a certain amount of real time has elapsed.

        The invoker of this method must invoke ServerPush.deactivate(boolean) in this finally clause.

        Note: the activation is applied to the desktop that was assigned by ServerPush.start(org.zkoss.zk.ui.Desktop).

        Unlike ServerPush.onPiggyback(), this method is NOT called in the context of an event listener. Rather, it is called in the thread of a server-push thread.

        Specified by:
        activate in interface ServerPush
        Parameters:
        timeout - the maximum time to wait in milliseconds. Ignored (i.e., never timeout) if non-positive.
        Returns:
        whether it is activated or it is timeout. The only reason it returns false is timeout.
        Throws:
        java.lang.InterruptedException - if it is interrupted by other thread
        DesktopUnavailableException - if the desktop is removed (when activating).

      • deactivate

        public boolean deactivate​(boolean stop)
        Description copied from interface: ServerPush
        Deactivates the current thread (which must be a server-push thread).
        Specified by:
        deactivate in interface ServerPush
        Parameters:
        stop - whether to stop after deactivate
        Returns:
        true if it is stopped
        See Also:
        ServerPush.activate(long)