So How Do You Code an AJAX Web Page? 231
PetManimal writes "Computerworld has a long excerpt from a book by Edmond Woychowsky about how to code Web pages in AJAX. It gives a good explanation of how the technology works, and also has some visuals and code snippets that you can play with. From the article: 'Beyond the XMLHTTP Request object, which has been around for several years as a solution looking for a problem, there is nothing weird needed. Basically, it is how the individual pieces are put together. When they're put together in one way, it is nothing more than a pile of parts; however, when put together in another way, the monster essentially rises from its slab.'"
So How Do You Code an AJAX Web Page? (Score:5, Informative)
2. Download and install the ATLAS framework
3. Wrap your webpage in an update panel
4. Add a script manager
5. Lather, rinse, and repeat
Seriously...one drag-and-drop and you'll never see another page refresh.
Printer Friendly (Score:5, Informative)
There are much better intros to Ajax (Score:5, Informative)
The article is very verbose. It has some value, I suppose - it helped me to decide I didn't want to buy the book. There are more concise introductions to Ajax here [www.xul.fr] and here [mozilla.org]
There is also an interesting library of Javascript/ECMAscript functions to perform common Ajax chores here [sourceforge.net]
Re:There are much better intros to Ajax (Score:3, Informative)
Use Echo2 (Score:5, Informative)
2. Write AJAX applications like you would a Swing app, never touching HTML or Javascript.
3. Go outside and play.
'nuff said.
Re:HTTP, time to update? (Score:2, Informative)
Re:HTTP, time to update? (Score:4, Informative)
There are some ugly hacks to allow the server to "push" to the client (embedded flash objects, never-closed-connections, etc.)--mostly encapsulated by the moniker COMET [ajaxian.com] (get it? Ajax... Comet...)
But if you get to pick your app server, there are some ready-made solutions. The problem with traditional web servers is their IO method. It's not their fault that the HTTP spec is out-of-date, but there are already new developments on the horizon that get around the current limitations. Take a look at GlassFish [java.net], Sun's new open-source enterprise application server, and pay particular attention to NIO [sun.com] socket writes. The performance benefits of NIO over straight IO are astonishing [java.net], with the side-benefit that it supports server-push out-of-the-box.
Not Magic (Score:3, Informative)
Useful bits I've found getting into ajax stuff:
Dojo Toolkit [dojotoolkit.org], a nifty framework for doing all sorts of good stuff. Of particular note to me was dojo.io.* with its dojo.io.bind() function, which provides a simple, cross-platform compatible way to do an xmlhttprequest, with callback functions for completion and errors, an easy way to post variables, specify a method and caching, etc.
openrico [openrico.org]. This provides all sorts of fun stuff. The smart stuff starts with declaring $ as a function, which after you get used to it provides a very convenient cross-platform way to access DOM nodes (ie, $('mydiv') or $(divvar)), and has all sorts of canned widgets for effects, like accordian widgets, move&resize, etc... although I've found practical application usually requires a bit more additional work, but their functions help get started.
Re:So How Do You Code an AJAX Web Page? (Score:3, Informative)
Nice troll, though.
Re:Saving AJAX (Score:3, Informative)
Re:So How Do You Code an AJAX Web Page? (Score:4, Informative)
Visual Studio actually has a pretty solid source code editor, with good syntax highlighting, and its code completion for css properties and html attributes is very good. (And its ability to offer effortless code completion for asp tags, AND user-defined controls is extremely helpful.) Not to mention its real-time "error" checking (improper tag nesting, mismatched tags, etc). It prevents and catches a lot of potential errors as you make them.
I do agree that doing a lot of work in the gui-designer results in bloated pages that need a ton of work to slim down and make crossplatform friendly. But nobody is forcing you to do that, and really if you know what you are doing you almost never use the visual designer mode. I only use it to drag user-controls onto the page; because in gui-mode it handles the boilerplate to register the tagprefix, etc. I also occasionally use it to create event handlers, because double clicking say a linkbutton in design view will write the boilerplate for the function signature, as well as handle the event wiring.
Like any tool, Visual Studio can be used effectively or ineffectively. When compared to most other "light tools" I find Visual Studio to be more productive -- sure I can build pages even in notepad but I make fewer typos when using the source code editor in Visual studio.
(There are other good editors too, don't get me wrong. I'm just saying that visual studio belongs among them.)
Re:Nobody calls XmlHttpRequest() directly anymore (Score:4, Informative)
What does that do that this doesn't (other than use a pretty wrapped package)? This is the general form I use for my AJAX requests. If needed, I add some checking to cancel previous requests to the same method or queue successive calls so that the race for responses doesn't screw me up. It seems to work in all browsers I test for (IE6, FF 1.5+, Opera 9+, Safari 2+...and yes, I force my users to use modern browsers).
if (window.XMLHttpRequest) {
var oHttpRequest= new XMLHttpRequest();
}
else if (window.ActiveXObject) {
var oHttpRequest = new ActiveXObject("Microsoft.XMLHTTP");
}
function ajaxCall (page,params,responseHolder) {
oHttpRequest.onreadystatechange=function()
if(oHttpRequest.readyState==4) {
document.getElementById(responseHolder).innerHTML = oHttpRequest.responseText;
}
}
oHttpRequest.open("POST",page,true);
oHttpRequest.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
oHttpRequest.send(params);
}
Re:So How Do You Code an AJAX Web Page? (Score:3, Informative)
And in the interest of full-disclosure, I recently started working for Microsoft on Visual Studio features directly related to AJAX and ATLAS. So now this post is just ordinary spam instead of a sneaky shill.
Re:Speaking of AJAX... (Score:5, Informative)
Re:Nobody calls XmlHttpRequest() directly anymore (Score:4, Informative)
The FormFaces [formfaces.com] OSS product is an entire XForms implementation done in JavaScript, running in the browser. You write your page in HTML with XForms markup, and FormFaces does the "HiJax" thing of re-writing it for you. You never need to use XmlHttpRequest, and you can interact with regular servers, RESTful services, etc., all via XML.
Another product that does this, in a slightly different way, is AjaxForms. I just found out about it, but it looks pretty good. AjaxForms uses some server-side components to do the translation from strict XHTML+XForms markup into Ajax (HTML4+JavaScript), but they claim it can work in PHP and Tomcat servers. Again, FOSS, and available at http://ajaxforms.sourceforge.net/ [sourceforge.net]
I recently implemented dynamic forms for weblogs and wikis, and did it using Chiba [sourceforge.net], another FOSS product, that like AjaxForms does its conversion on the server, using Tomcat as a container.
Another important option is the work that the Mozilla Foundation and IBM are doing to make a native implementation of XForms as an XPI for Firefox and Mozilla. See http://www.mozilla.org/projects/xforms/ [mozilla.org] -- they're now in version 0.6, with 1.0 targeting full XForms 1.0 compliance. Like all other Mozilla extensions, it's a 1-click install, and I think it's about 200KB, so it's not very big, and I hope it gets added to the default build after it reaches 1.0. (It's presently built with the nightlies.)
There are a number of other implementations, including browser plugins (FormsPlayer [formsplayer.com] for IE), native implementations for embedded devices such as cellphones and kiosks (PicoForms [picoforms.com], SolidForms [sourceforge.net], and entire server-side systems using XForms, such as Orbeon Ops [orbeon.com], so I see an increasingly bright future for using XForms to build dynamic HTML interfaces on top of XML web services and deploy them across a range of devices.
Re:So How Do You Code an AJAX Web Page? (Score:5, Informative)
However, for the web impaired here is a direct link [microsoft.com] for the web developer version only (which you can get to by clicking the big download picture on the right hand side of each product specific page and then clicking "Download" in step 2).
And as long as I am providing overly simple instructions to trolls, I guess I'll point out that ATLAS does not come installed with Visual Studio. You have to download it from atlas.asp.net [asp.net] (hint: there is a big download icon at the top of the screen).
And if you would like a demo of how easy it is to create ajax applications with atlas, there is current a video [microsoft.com] on the front page of someone creating a database backed todo-list application in 18 minutes (the express version of Visual Studio comes with a lightweight database and web server for development. I think you can probably repeat this demo with the free tools).
Re:Saving AJAX (Score:2, Informative)
Very simple when using prototype javascript library.
function submitForm(form) {
new Ajax.Request("comment.php", {
parameters : Form.serialize(form),
onSuccess : updateComment
});
}
Re:Time to put up or shut up (Score:3, Informative)
Off the top of my head: Google Suggest [google.com]. The same page offers enhanced Ajax functionality and still works in Lynx, without any need for two pages or radically different layouts.
The ways you make Ajax work in a backwards-compatible manner are the same techniques decent JavaScript developers have been using for years. Unfortunately, not a lot of people are aware of JavaScript best practices and the field is still dominated by people who concentrate on making it work in their favourite browser and then bodging it to work elsewhere, rather than starting from a good solid design and enhancing it in a structurally sound manner.
If you're interested in learning more, I suggest DOM Scripting [domscripting.com] and the DOM Scripting Task Force website [webstandards.org] as decent starting points. I haven't read the book, but I've heard a lot of good things about it from people who know what they are talking about.
uhm (Score:1, Informative)