Interface ServerPush
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- All Known Implementing Classes:
CometServerPush
,CometServerPush
,PollingServerPush
,WebSocketServerPush
public interface ServerPush
Represents a server-push controller. A server-push controller is a plugin to provide the server-push feature for ZK. A server-push thread is a working thread that want to manipulate a desktop whenever it wants, rather than in an event listener.There are several to implement (or, to simulate) the server-push feature on a HTTP-based application.
First, the server-push feature can be simulated by client's polling. That is, the client polls the server for executing any pending server-push threads. The client can adjust the frequency based on the response time (in proportion to the server load) (see
PollingServerPush
for details). To poll, the client usually send the dummy command that does nothing but triggeronPiggyback()
to be execute.Second, the server-push feature can be implemented by maintaining a persistent connection between client and server. It is also called Comet (see also Comet).
Third, the server-push feature can be simulated in a passive way. That is, it doesn't poll at all. Rather
onPiggyback()
is called automatically when the user trigger some other events.- Since:
- 3.0.0
- Author:
- tomyeh
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Method Summary
All Methods Instance Methods Abstract 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).boolean
isActive()
Returns if the working thread of the server push is active.void
onPiggyback()
Called whenEvents.ON_PIGGYBACK
is received.void
resume()
Resumes server-push - this is required after desktop recycling.<T extends Event>
voidschedule(EventListener<T> task, 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.void
stop()
Stops and cleans up the server-push controller.
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Method Detail
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isActive
boolean isActive()
Returns if the working thread of the server push is active. In other words, it is true if it is betweenExecutions.activate(org.zkoss.zk.ui.Desktop)
andExecutions.deactivate(org.zkoss.zk.ui.Desktop)
.- Since:
- 3.5.2
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start
void start(Desktop desktop)
Starts and initializes the server-push controller. One server-push controller is associated with exactly one desktop.start(org.zkoss.zk.ui.Desktop)
is called whenDesktop.enableServerPush(boolean)
is called to enable the server-push feature for the specified desktop.
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stop
void stop()
Stops and cleans up the server-push controller.stop()
is called whenDesktop.enableServerPush(boolean)
is called to disable the server-push feature, or when the desktop is being removed.
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resume
void resume()
Resumes server-push - this is required after desktop recycling. (added ServerPush interface to fix ZK-1777)resume()
is called whenUiEngine.recycleDesktop(org.zkoss.zk.ui.Execution, org.zkoss.zk.ui.Page, java.io.Writer)
is called to resume a previously enabled server-push on the recycled desktop.- Since:
- 6.5.4
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schedule
<T extends Event> void schedule(EventListener<T> task, T event, Scheduler<T> scheduler)
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.
- Parameters:
task
- the task to executeevent
- 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.- Since:
- 5.0.6
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activate
boolean activate(long timeout) throws java.lang.InterruptedException, DesktopUnavailableException
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
deactivate(boolean)
in this finally clause.Note: the activation is applied to the desktop that was assigned by
start(org.zkoss.zk.ui.Desktop)
.Unlike
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.- 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 threadDesktopUnavailableException
- if the desktop is removed (when activating).
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deactivate
boolean deactivate(boolean stop)
Deactivates the current thread (which must be a server-push thread).- Parameters:
stop
- whether to stop after deactivate- Returns:
- true if it is stopped
- Since:
- 3.5.2
- See Also:
activate(long)
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onPiggyback
void onPiggyback()
Called whenEvents.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()
.
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