JVx with vaadin UI and server-side push
Vaadin supports "push" - since 7.1 - but JVx doesn't have an API for that. It's technology dependent and we usually not need it on client-side of an application. It would be useful for the server-side of JVx applications, but that's a different thing. I want to write about server-side push for UI changes.
If you use threads in your application, to update the UI, it's not a problem if you use a desktop technology like Swing UI. The UI is always up-to-date. If you use vaadin UI, it's not the case, because vaadin UI runs on an application server (= server machine) and vaadin client runs in your browser as Javascript code (= client machine). The thread runs on the server machine and doesn't update the client machine automatically. The client retrieves all changes with next client request. This is sometimes too late. With server-side push it's possible to update the client machine immediate, if you use pure vaadin.
With our next vaadin UI release, it's also possible to use server-side push of vaadin to update the client machine. It's very easy to use and also is technology independent, but we didn't introduce new APIs 
How it works?
Create a new thread, through your factory and use invokeLater to update the UI. You always should use invokeLater to update the UI (no difference if you use swing or other desktop technologies).
{
public void run()
{
try
{
while (!ThreadHandler.isStopped())
{
Thread.sleep(2000);
UIComponent.invokeLater(new Runnable()
{
public void run()
{
iCount++;
label.setText("Push: " + iCount);
}
});
}
}
catch (InterruptedException ie)
{
info(ie);
}
}
});
If push is enabled, above code pushes the UI changes immediate to the client machines. To enable server-side push, simply add following to your servlet configuration in web.xml:
<param-name>pushmode</param-name>
<param-value>automatic | manual</param-value>
</init-param>
<async-supported>true</async-supported>
It's also possible to use vaadin push without JVx' mechanism (pure vaadin). To see how this works, read following issue: Server-side refresh.
Development | rjahn | 18/11/2013
RSS-Feed