Last year we had described how to use DWR (Direct Web Remoting) with GlassFish (check the relevant entries); now JFA shows how to do Reverse AJAX using DWR and GlassFish, via Grizzly. It is as simple as:

Download GlassFish and install it. See instruction here. Download dwr.war % cd ${glassfish.home}/bin % ./asadmin set server.http-service.http-listener.http-listener-1.property.cometSupport=true % Start (or restart) GlassFish % ./asadmin deploy /path/to/dwr.war

Details at JFA's entry. Added: Also check the corresponding entry at Comet Daily.

SDN is doing a series of articles on Hands-On Java EE and they are starting with AJAX. Mark and Rick are planning 4 articles in increasing complexity and so far have published two: the first one deals with Do-it-yourself, where the developer uses JavaScript and DHTML directly, while the second shows how to Use a Toolkit focusing specially on using the Dojo Toolkit, which is what Sun has standarized around.

In a related, longer, article, Mark and Ed provide a fairly complete review of the AJAX Design Strategies covering the two shown in the previous articles (do-it-yourself and client-side toolkit) as well as four others: a server framework like JSF or others, jMaki wrappers, Remote Invocation like DWR, and a pure-java like GWT.

AJAX manipulates the local representation of a Web page using JavaScript and updates it with content (usually XML or JSON) that is fetched dynamically using HTTP. AJAX is becoming very popular because it avoids page refreshes and provides a more dynamic interface but one of its challenges is how to avoid stale data; there are a number of techniques to address this, including polling, piggybacking and long-lived HTTP connections. These approaches have been around for a while in one way or another but, like AJAX, are becoming more popular and are being given different names. For example, the collection of technologies is called Reverse AJAX in DWR 2.0 (blog, Intro@Prokata). And the usef of long-lived HTTP connections, also called HTTP Streaming is also called Comet. Comet is particularly interesting in that it has an impact in the programming model and in the implementation. There is beginning to be enough experience with the model (AsyncWeb, LightStreamer, Jetty's@TSS) to start thinking of standarization and GregW and others have advocated along this direction. One of the interesting developments is that the Grizzly's machinery provides a very good foundation for Comet -- see for example the report from AgileAjax, and Jean-Francois and others are talking about using it more widely in that direction. I hope this will make it into one of our future releases of GlassFish.

PS. The name Comet is a takeoff on AJAX. This is possibly more of a US-centered joke, so check... AJAX's site (a brand of Colgate-Palmolive) and Comet's site (a brand of Prestige Brands, Inc).

I have found a few articles that talk about some "side affects" of the current AJAX hype. One talks about AJAX in your Content Management System and how CMS uses AJAX to help you develop your web app more easily now and how the CMS may support adding AJAX components in your web app. With the release of DWR 2.0 came the term reverse AJAX which addresses the fact that the server may want to communicate with the browser but the browser isn't used to listening (hmm, sounds like my kids). Finally Paul discusses web 2.0, storage and infrastructure that might be needed to get to all that data.

DWR (Direct Web Remoting) is a Servlet that can be used to provide AJAX support by generating JavaScript code from Java classes (web site, overview, Java.Net project). Check the examples and here is a Quicktime Movie of a site using DWR. Masoud just tested that DWR works with the latest GlassFish build. As an extra bonus, Masoud also describes different ways of deploying into GlassFish.