org.zkoss.zkex.ui.comet
Class CometServerPush

java.lang.Object
  org.zkoss.zkex.ui.comet.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

static interface

CometServerPush.AsyncInfo The interface for implementing asynchronous processing.

Constructor Summary

CometServerPush()

Method Summary

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

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).

isActive

public boolean isActive()

Description copied from interface: ServerPush

Returns if the working thread of the server push is active. In other words, it is true if it is between Executions.activate(org.zkoss.zk.ui.Desktop) and Executions.deactivate(org.zkoss.zk.ui.Desktop).

Specified by:

isActive in interface ServerPush

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)