Package org.zkoss.zkex.ui.comet

Class CometServerPush

  • All Implemented Interfaces:
    ServerPush
    Direct Known Subclasses:
    CometServerPush
    public class CometServerPush
extends java.lang.Object
implements ServerPush
    A server-push implementation that is based on comet. This implementation is compatible with any version of Servlet. It also means it doesn't utilize Servlet 3 asynchronous processing support. If you are using Servlet 3 servers, it is recommended to use CometServerPush instead.

    Available in ZK PE.

    Since:
    6.0.0
    Author:
    tomyeh

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static interface  CometServerPush.AsyncInfo
      The interface for implementing asynchronous processing.
      protected static class  CometServerPush.ThreadInfo
      The info of a server-push thread.

    • Constructor Summary

      Constructors 
      Constructor Description
      CometServerPush()  

    • 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).
      protected void beforeUpdate​(CometServerPush.ThreadInfo info)  
      boolean deactivate​(boolean stop)
      Deactivates the current thread (which must be a server-push thread).
      Desktop getDesktop()
      Returns the desktop that this server push belongs to (never null).
      protected int getIntPref​(java.lang.String key)
      Retrieve the integer preference by the given key.
      protected java.lang.String getStartScript()
      Returns the JavaScript codes to enable (a.k.a., start) the server push.
      protected java.lang.String getStartScript​(java.lang.String zkediton)  
      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.
      protected void onStart()
      Called when start(org.zkoss.zk.ui.Desktop) is called.
      protected void onStop()
      Called when stop() is called.
      protected void processRequest​(Execution exec, CometServerPush.AsyncInfo ai)
      Called when receiving the comet request from the client.
      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.
      protected boolean setBusy()
      Sets busy and return if it is busy for processing other request.
      void start​(Desktop desktop)
      Starts the server push.
      protected void startClientPush()
      Sends an AU response to the client to start the server push.
      void stop()
      Stops the server push.
      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

      • CometServerPush

        public CometServerPush()

    • 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.

        The default implementation is to send an AuScript response to contain the script specified in a preference called CometServerPush.start, or the script returned by getStartScript(), if the preference is not found. 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 an AuScript instance to contain the script specified in a preference called CometServerPush.stop,' or the script returned by getStopScript(), if the preference is not found. 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.

      • getStartScript

        protected java.lang.String getStartScript​(java.lang.String zkediton)

      • getIntPref

        protected int getIntPref​(java.lang.String key)
        Retrieve the integer preference by the given key. Visibility set to protected so that zkmax can have access to this method.

      • 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.

      • getDesktop

        public Desktop getDesktop()
        Returns the desktop that this server push belongs to (never null).

      • start

        public void start​(Desktop desktop)
        Starts the server push.

        The derived class rarely need to override this method. Rather, override startClientPush().

        Specified by:
        start in interface ServerPush

      • resume

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

      • stop

        public void stop()
        Stops the server push.

        The derived class rarely need to override this method. Rather, override stopClientPush().

        Specified by:
        stop in interface ServerPush

      • onStart

        protected void onStart()
        Called when start(org.zkoss.zk.ui.Desktop) is called. This method is called before startClientPush(), and used to initialize the desktop, if necessary.

        The default implementation initializes an extension to process the comet request.

      • onStop

        protected void onStop()
        Called when stop() is called. This method is called after stopClientPush() is called and this server push has been cleaned up.

        The default implementation does nothing.

      • 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.

      • setBusy

        protected boolean setBusy()
        Sets busy and return if it is busy for processing other request. If it is busy, true is returned. If it is not busy, false is returned but it is marked as busy.

        It is possible since the client might abort the previous one and issue a new one but their server didn't know.

      • processRequest

        protected void processRequest​(Execution exec,
                              CometServerPush.AsyncInfo ai)
                       throws java.io.IOException
        Called when receiving the comet request from the client.
        Throws:
        java.io.IOException

      • 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)