public interface ServerPush
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 trigger onPiggyback()
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.
Modifier and Type | Method and 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 when
Events.ON_PIGGYBACK
is received. |
void |
resume()
Resumes server-push - this is required after desktop recycling.
|
<T extends Event> |
schedule(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.
|
boolean isActive()
Executions.activate(org.zkoss.zk.ui.Desktop)
and
Executions.deactivate(org.zkoss.zk.ui.Desktop)
.void start(Desktop desktop)
start(org.zkoss.zk.ui.Desktop)
is called when Desktop.enableServerPush(boolean)
is called to enable the server-push feature for the specified
desktop.
void stop()
stop()
is called when Desktop.enableServerPush(boolean)
is called to disable the server-push feature, or when the desktop
is being removed.
void resume()
resume()
is called when UiEngine.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.
<T extends Event> void schedule(EventListener<T> task, T event, Scheduler<T> scheduler)
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.
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.boolean activate(long timeout) throws java.lang.InterruptedException, DesktopUnavailableException
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.
timeout
- the maximum time to wait in milliseconds.
Ignored (i.e., never timeout) if non-positive.java.lang.InterruptedException
- if it is interrupted by other threadDesktopUnavailableException
- if the desktop is removed
(when activating).boolean deactivate(boolean stop)
stop
- whether to stop after deactivateactivate(long)
void onPiggyback()
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()
.
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