✎ Push support | Documentation

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~~NOTRANS~~
~~Title: Push support~~

Sometimes it's important to notify all client about an event or about changed records. This is known as "push". You push a message to all clients. In web environments a websocket is used for push notification. In JVx we have a [[jvx:communication:push_publish|push mechanism]] which is technology independent and it works different in different UI technologies.

How to push a message to other clients?

In our example, we have a button and on button press we send a simple reload notification to all other clients. This is a super simple task.

The action event for the button looks like:

<file java>
public void doSendNotification(UIActionEvent pEvent) throws Throwable
{
    //saves all changes
    save();
	
    //triggers push
    getConnection().callAction("doReloadAllClients");
}
</file>
In our [[jvx:server:lco:lifecycle|life-cycle]] object, we need the ''doReloadAllClients'' method:
<file java>
public void doPublish()
{
    ICallBackBroker broker = SessionContext.getCurrentCallBackBroker();
	
    Thread th = new Thread(new Runnable()
    {
        public void run()
        {
            broker.publish("RELOAD", null, PublishMode.AllOtherMasterSessions);						
        }
    });
    th.start();
    
    //with JVx 3.0, not additional thread is required
    //SessionContext.getCurrentCallBackBroker().publish("RELOAD", null, PublishMode.AllOtherMasterSessions);
}
</file>
The reload event needs a handler. This handler/listener will be registered in our application:
<file java>
public class CustomApplication extends Application
                               implements ICallBackResultListener
{
    @Override
    public void setConnection(AbstractConnection pConnection)
    {
        AbstractConnection con = getConnection();
        if (con != null)
        {
            con.removeCallBackResultListener(this);
        }
    
        super.setConnection(pConnection);
    
        pConnection.addCallBackResultListener(this);
    }

    public void callBackResult(CallBackResultEvent pEvent)
    {
        if ("RELOAD".equals(pEvent.getInstruction()))
        {
            try
            {
                reload();
            }
            catch (Throwable th)
            {
                error(th);
            }
        }
    }
}    
</file>

That's it.

But be careful, because push won't work in load-balanced applications with this standard implementation!