public class ServerPushSession
extends java.lang.Object
Due to the request-response nature of HTTP, the client does not automatically notice UI updates
that happen outside of the UI thread (i.e. outside of a request). This is the case when e.g.
Display.asyncExec()
is called from a background thread. Therefore, the framework
provides a mechanism called server push that maintains a standing connection to refresh
the client immediately in case of a UI update.
To activate the server push, create and start a ServerPushSession. Normally, the server push is only needed for a certain period of time, e.g. while a background task is running and keeps updating a progress bar. The push session should be stopped when it is no longer needed to allow the server to free resources related to the server push.
Several independent server push sessions can be created and started in parallel within the same UISession. As long as there is at least one server push session running, the server push will remain active. A server push session can be re-used, i.e. started and stopped multiple times. If not stopped explicitly, all server push sessions will be stopped when the UI session terminates.
Example code:
final ServerPushSession pushSession = new ServerPushSession(); Runnable bgRunnable = new Runnable() { public void run() { // do some background work ... // schedule the UI update display.asyncExec( new Runnable() { public void run() { if( !widget.isDisposed() ) { label.setText( "updated" ); } } } ); // close push session when finished pushSession.stop(); } ); }; pushSession.start(); Thread bgThread = new Thread( bgRunnable ); bgThread.setDaemon( true ); bgThread.start();
Display.asyncExec(java.lang.Runnable)
,
Display.syncExec(java.lang.Runnable)
,
Display.wake()
Constructor and Description |
---|
ServerPushSession()
Creates a new ServerPushSession for the current UISession.
|
public ServerPushSession()
java.lang.IllegalStateException
- when called from a non-UI threadpublic void start()
This method must be called from the UI thread.
java.lang.IllegalStateException
- when called from a non-UI threadpublic void stop()
This method may be called from a background thread.
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