ZK Serve Push with Java Timer

Introduction

This article describe how to use Server Push (long pooling) with java.util.Timer in ZK.

NOTE: This feature require ZK EE.

Result

View demo on line
http://screencast.com/t/CIhJVqw7lgDK

Program

index.zul

Simple zul page.

<zk>
    <div apply="test.TestComposer">
        <intbox id="ibx" readonly="true" />
        <button id="startBtn" label="start" />
        <button id="stopBtn" label="stop" />
    </div>
</zk>

TestComposer.java

Start/stop Server Push with button click.

package test;

import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.atomic.AtomicInteger;

import org.zkoss.zk.ui.Desktop;
import org.zkoss.zk.ui.Executions;
import org.zkoss.zk.ui.select.SelectorComposer;
import org.zkoss.zk.ui.select.annotation.Listen;
import org.zkoss.zk.ui.select.annotation.Wire;
import org.zkoss.zul.Intbox;
/**
 * Tested with ZK 6.0.2
 * @author benbai123
 *
 */
@SuppressWarnings("rawtypes")
public class TestComposer extends SelectorComposer {

    private static final long serialVersionUID = 5928314519324520566L;
    @Wire
    Intbox ibx;
    private final AtomicInteger _cnt = new AtomicInteger(0);
    private Timer timer;
    @Listen("onClick = #startBtn")
    public void start () {
        final Desktop desktop = Executions.getCurrent().getDesktop();
        if (!desktop.isServerPushEnabled()) {
            // enable server push if not enabled
            desktop.enableServerPush(true);
            timer = new Timer();
            // schedule task
            // getTask() -> get the task that to be scheduled
            // 0 -> no delay of first task, start it immediately
            // 1000 -> delay between each task after first task, 1 sec here
            timer.schedule(getTask(), 0, 1000);
        }
    }
    @Listen("onClick = #stopBtn")
    public void stop () {
        final Desktop desktop = Executions.getCurrent().getDesktop();
        if (desktop.isServerPushEnabled()) {
            // disable server push if enabled
            desktop.enableServerPush(false);
            // cancel scheduled task
            timer.cancel();
        }
    }
    // task to be scheduled
    public TimerTask getTask () {
        return new TimerTask() {
            public void run () {
                update();
            }
        };
    }
    // update value of intbox
    public void update () {
        Desktop desktop = ibx.getDesktop();
        try {
            if(desktop == null) {
                timer.cancel();
                return;
            }
            try {
                // active desktop
                Executions.activate(desktop);
                // update UI
                ibx.setValue(_cnt.getAndIncrement());
            } finally {
                // deactive desktop
                Executions.deactivate(desktop);
            }
        } catch (Exception ignore) {
            /* ignore */
        }
    }
}

Reference

Sample at zkdemo
http://www.zkoss.org/zkdemo/server_push/comet


Download

Full project at github
https://github.com/benbai123/ZK_Practice/tree/master/Pattern/ServerPush/ServerPushWithJavaTimer

Demo Flash
https://github.com/benbai123/ZK_Practice/blob/master/demo_src/swf/Pattern/ServerPush/ServerPushWithJavaTimer.swf