The <a4j:push> periodically perform AJAX request to server, to simulate 'push' data.

The main difference between <a4j:push> and <a4j:poll> components is that <a4j:push> makes request to minimal code only (not to JSF tree) in order to check the presence of messages in the queue. If the message exists the complete request will be performed. The component doesn't poll registered beans but registers EventListener which receives messages about events.

Attribute 'interval' is used as for poll component. It specifies the interval in ms. for call push request. Simple example of usage:

Thus, component 'push' uses asynchronous model instead of polls.

There is simple Push example using Runabble interface.

When you hit Start button new Thread will be started and alive for a minute. It will generate random Uuid once in a ten seconds.

Push component will fire the request after uuid generation event sent and update the output field displaying new uuid value.

Push Demo

Push Example

Press Start to run push example

HideView Source

<ui:composition xmlns="http://www.w3.org/1999/xhtml"
    xmlns:ui="http://java.sun.com/jsf/facelets"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:a4j="http://richfaces.org/a4j"
    xmlns:rich="http://richfaces.org/rich">

    <h:form>
        <a4j:push interval="1000" eventProducer="#{push.addListener}"
            reRender="push,out" enabled="#{push.enabled}" id="push"/>
        <rich:panel>
        <f:facet name="header">
            <h:outputText value="Push Example"/>
        </f:facet>
        <h:panelGrid columns="1" id="out">
            <h:outputText rendered="#{!push.enabled}" value="Press Start to run push example"/>
            <h:panelGroup rendered="#{push.enabled}">
                <h:outputText value="Generated UUID:"/>
                <h:outputText value="#{push.uuid}"/>
            </h:panelGroup>
            <h:panelGroup>
                <a4j:commandButton value="Start" action="#{push.start}"
                    ajaxSingle="true" rendered="#{!push.enabled}" reRender="push, out"/>
                <a4j:commandButton value="Stop" action="#{push.stop}"
                    ajaxSingle="true" rendered="#{push.enabled}" reRender="push, out"/>
            </h:panelGroup>
        </h:panelGrid>
        </rich:panel>
    </h:form>
</ui:composition>

<<Hide Source

HideView PushBean.java Source

/**
 * 
 */
package org.richfaces.demo.push;

import java.util.Date;
import java.util.EventListener;
import java.util.EventObject;
import java.util.UUID;

import org.ajax4jsf.event.PushEventListener;

/**
 * @author Ilya Shaikovsky
 * 
 */

public class PushBean implements Runnable {

    private String uuid = "";
    
    private boolean enabled = false;
    
    private Date startDate; 
    
    PushEventListener listener;

    private Thread thread;

    // private int eventsFired counter;

    public void addListener(EventListener listener) {
        synchronized (listener) {
            if (this.listener != listener) {
                this.listener = (PushEventListener) listener;
            }
        }
    }

    public void run() {
        while (thread != null) {
            try {
                if (((new Date()).getTime()-startDate.getTime())>=60000) {
                    stop();
                }
                uuid = UUID.randomUUID().toString();
                listener.onEvent(new EventObject(this));
                Thread.sleep(10000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                // e.printStackTrace();
            }
        }
    }

    public String getUuid() {
        return uuid;
    }

    public void start() {
        if (thread == null) {
            thread = new Thread(this);
            thread.setDaemon(true);
            thread.start();
            setStartDate(new Date());
            setEnabled(true);
        }
    }

    public void stop() {
        if (thread != null) {
            //thread.stop();
            setStartDate(null);
            setEnabled(false);
            thread = null;
        }
    }

    public Thread getThread() {
        return thread;
    }

    public boolean isEnabled() {
        return enabled;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

    public Date getStartDate() {
        return startDate;
    }

    public void setStartDate(Date startDate) {
        this.startDate = startDate;
    }
}

<<Hide Source