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Better Web Apps With Ajax
An anonymous reader wrote to mention an article on IBM's site detailing the fundamentals of Java-based Ajax. From the article: "This article gives you a good understanding of the fundamental principles of Ajax, and a nuts-and-bolts knowledge of the client and server side components that participate in an Ajax interaction. These are the building blocks of a Java-based Ajax Web application. In addition, you will be shown some of the high-level design issues that come with the Ajax approach."
I'm glad to see another serious technical article on the pros and cons of implementing an AJAX solution. Most everyone who says the acronym "AJAX" usually falls into one of two camps - either the "OMFGZ teh AJAX is so amazing! It will change the interweb!" How? Oh, it allows parts of the page to be updated without a refresh. How interesting. Perhaps you could go a little more in-depth? No? Thanks...
The other camp... too many Slashdotters, IMO... feel the need to flex their superior understanding of the fundamental dynamics of the internet and development and offer this gem: "AJAX is just an assortment of pre-existing technologies. Nothing to see here".
The automobile was just an assortment of pre-existing technologies, and it radically changed the world. It also introduced a whole bevy of new challenges, both technical and otherwise, that we still haven't fully figured out yet. It was not a transportation panacea, and AJAX is no cure-all. But just because it doesn't solve every problem doesn't mean it doesn't have the power to be revolutionary.
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Here's a screenshot:
Atlas is Microsoft's entry into the suddenly-popular-even-though-it-has-been-around-fo r-7-or-more-years AJAX trend.
Atlas is a set of extensions to ASP.NET 2.0 that allows for web developers to use AJAX with little or no plumbing work on their part.
It integrates with ASP.NET extremely well and maintains the "event driven" style that ASP.NET is known for.
There is also a Channel 9 video about what Microsoft is doing on the AJAX front elsewhere.
Why? Less verbose (easier on bandwidth) and no parsing (ever tried parsing XML using XmlHttpRequest? It sucks). JSON is object syntax. It is a real, live object serialized to string.
It just so happens that JSON is also legal Python object notation.
Hmmm... GMail, Google Maps, Google Suggest... none of these use XML. Google is also renowned for using Python. JSON syntax is the same in client-side javascript and server-side python... hmmm... makes me think twice, anyway, instead of drinking the web services kool-aid Sun and Microsoft are serving.
First, Unicode under JSON is abit exciting. In XML there are no surprises.
Secondly, XML is transported over HTTP 90% of the time.
Almost all modern HTTP implementations implement GZIP as an encoding. If you don't already have this enabled in your servers, then you don't really care about bandwidth utilization.
JSON offers nothing useful over XML+GZIP (which is a transport/encoding issue anyway). It can, however, make it vastly more difficult to interchange your data and tie you to a limited object model. If anything, I support the process used by the W3C. I like their standards. JSON is nice, but not nice enough. Sorry guys.
Learn XML. Learn XPATH. Try to use Twisted's XMLSTREAM implementation for a taste of how easy and flexible it can be. Write some Jabber apps. JSON can't really be in those spaces. Not anytime soon at least.
I think Mauve has the most RAM. --PHB (Dilbert Comic)
"Its not just for XML and its not just a J language either... Ruby will do."
No, XML isn't really a requirement of functionality. If by J you mean a Java backend, you are correct, but not if you mean Javascript Without Javascript you cannot have AJAX-like functionality unless you use a plugin or browser addon like JRE, Flash, etc.
I just wanted to clarify this point to those who might take that statement the wrong way. Coding something in C++ that talks to a server is not AJAX, for instance. AJAX, imho, is defined by 3 characteristics.
1. AJAX involves dynamic content, not static content. This means that there is a seemless interaction, without the application appearing to "reload".
2. AJAX involves a stand alone web browser or an embeded web browser that is running the common scripting language Javascript.
3. AJAX involves data retrival from a source outside of the client-side application itself, and does not solely use data embedded in the application itself.
I could refine those a bit, but I think the general ideas come across. So, really, a Java applet embeded in your browser that talks to the server, such as an IRC chat client, is not AJAX, though it may provide AJAX-like functionality. The language of the backend is irrelevant; the data formats are irrelevant. The only relevance, really, is that you are taking something that has generally been static (web pages) and made the operate like a fully functioning application. It's the transition from "Information" (HTML) to "Application" (AJAX).
The definition really can't go beyond this. If it isn't limitted to seemless dynamic content, you could call any webpage that contained Javascript AJAX. If it isn't limitted to browsers and Javascript, then you could call an SSH program, chat applet, multiplayer game XBOX game, etc. "AJAX clients". If it isn't limitted to outside data, then you'd have to call Javascript clocks AJAX. An application must (at least) satisfy these three conditions before it can be called AJAX. If it doesn't, it may still be a really good interactive and dynamic application, though not AJAX.
The core of AJAX, XMLHttpRequest, is the only place I think the term XML is validated in the AJAX acronym. And, certainly, you can load any type of data you wish with it. If there was any single thing to define AJAX, it is this command. Without it (or something like it coded in a round about way... who knows, some people like the challenge) you cannot satisfy all 3 conditions.
I8-D