Push

Push Project

NOTE: this documentation applies to wicket push version 1.4.16 or higher.

The Wicket Push project provides support for Reverse AJAX in Wicket applications and allows them to "push" partial Web page updates to the Web browser.

The push projects comes with two implementations:

1. push-timer: a polling based approach where the web page continuously polls the server for page updates via AJAX (similar to AjaxSelfUpdatingTimerBehavior)

2. push-cometd: the web pages connects to the web application via a stateful Cometd channel on which the server sends update requests to the browser on demand. Note: Cometd requires the Servlet 3.0 specification.

Maven Artifacts

• push-core
• push-timer
• push-cometd

Documentation

Maven Stable

<dependency>
    <groupId>org.wicketstuff</groupId>
    <artifactId>push-timer</artifactId>
    <version>1.4.17</version>
</dependency>

Maven Development

<dependency>
    <groupId>org.wicketstuff</groupId>
    <artifactId>push-cometd</artifactId>
    <version>1.4-SNAPSHOT</version>
</dependency>

<repository>
    <id>wicketstuff-core-snapshots</id>
    <url>https://oss.sonatype.org/content/repositories/snapshots</url>
    <snapshots>
        <enabled>true</enabled>
    </snapshots>		
</repository>

Usage

The general usage pattern of wicket-push is:

1. Create a class implementing IPushEventHandler containing the logic that updates the UI when a Push event occurs. Such an event is usually raised by a background service, e.g. chat service raising a MessageReceivedEvent.
2. Obtain a reference to a IPushService implementation in your Wicket Panel.
3. Use the push service to install a push node holding a reference to your push event handler into one of the panel's components. This will add the required client-side push markup to that component.
4. Add a listener to your (asynchronous) background service and forward the raised events via the Push service to your Push event handler. This will ensure that the update code is handled in the right Wicket HTTP request thread.

Here is an example:

/*
 * panel constructor
 */
public ChatPanel()
{
    // setup UI components ...

    /*
     * 1. instantiate push event handler
     */
    IPushEventHandler handler = new AbstractPushEventHandler<Message>()
    {
        public void onEvent(AjaxRequestTarget target, Message message, IPushNode<Message> node, IPushEventContext<Message> ctx)
	{
                // TODO your component update logic goes here...
	}
    });

    /*
     * 2. obtain a reference to a Push service implementation
     */
    IPushService pushService = TimerPushService.get();

    /*
     * 3. install push node into this panel
     */
    IPushNode<Message> pushNode = pushService.installNode(this, handler);

    /*
     * 4. connect to the chat service and forward the Message events to the push node and it's event handler
     */
    IChatService chatService = ServiceLocator.getChatService();
    chatService.addListener(new IChatListener() {
        public void onMessage(Message msg)
        {
            if (pushService.isConnected(pushNode))
                // forward the Message event via the push service to the push event handler
                pushService.publish(pushNode, msg);
            else
                chatService.removeListener(this);
        }
    });
}

Project Maintainers

Active:

• Rodolfo Hansen
• Sebastian Thomschke

Retired:

• Vincent Demay

Source Code

core-1.4.x Branch

• jdk-1.5-parent/push-parent-jdk-1.5
• jdk-1.6-parent/push-parent-jdk-1.6

master Branch

• jdk-1.5-parent/push-parent-jdk-1.5
• jdk-1.6-parent/push-parent-jdk-1.6