11 :: Won't my server-side framework provide me with AJAX?
You may be benefiting from AJAX already. Many existing Java based frameworks already have some level of AJAX interactions and new frameworks and component libraries are being developed to provide better AJAX support. I won't list all the Java frameworks that use AJAX here, out of fear of missing someone, but you can find a good list at www.ajaxpatterns.org/Java_Ajax_Frameworks.If you have not chosen a framework yet it is recommended you consider using JavaServer Faces or a JavaServer Faces based framework. JavaServer Faces components can be created and used to abstract many of the details of generating JavaScript, AJAX interactions, and DHTML processing and thus enable simple AJAX used by JSF application developer and as plug-ins in JSF compatible IDE's, such as Sun Java Studio Creator.
12 :: What Browsers does HTML_AJAX work with?
As of 0.3.0, all the examples that ship with HTML_AJAX have been verified to work with* Firefox 1.0+
* Internet Explorer 5.5+ (5.0 should work but it hasn't been tested)
Most things work with
* Safari 2+
* Opera 8.5+
13 :: What browsers support AJAX?
Internet Explorer 5.0 and up,Opera 7.6 and up,
Netscape 7.1 and up,
Firefox 1.0 and up,
Safari 1.2 and up,
among others support AJAX.
14 :: What do I do on the server to interact with an AJAX client?
The "Content-Type" header needs to be set to"text/xml". In servlets this may be done using the HttpServletResponse.setContentType()should be set to "text/xml" when the return type is XML. Many XMLHttpRequest implementations will result in an error if the "Content-Type" header is set The code below shows how to set the "Content-Type".response.setContentType("text/xml");
response.getWriter().write("
You may also want to set whether or not to set the caches header for cases such as autocomplete where you may want to notify proxy servers/and browsers not to cache the results.
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
response.getWriter().write("
Note to the developer: Internet Explorer will automatically use a cached result of any AJAX response from a HTTP GET if this header is not set which can make things difficult for a developer. During development mode you may want set this header. Where do I store state with an AJAX client.
15 :: What do I need to know to create my own AJAX functionality?
If you plan not to reuse and existing AJAX component here are some of the things you will need to know.Plan to learn Dynamic HTML (DHTML), the technology that is the foundation for AJAX. DHTML enables browser-base realtime interaction between a user and a web page. DHTML is the combination of JavaScript, the Document Object Model (DOM) and Cascading Style Sheets (CSS).
* JavaScript - JavaScript is a loosely typed object based scripting language supported by all major browsers and essential for AJAX interactions. JavaScript in a page is called when an event in a page occurs such as a page load, a mouse click, or a key press in a form element.
* DOM - An API for accessing and manipulating structured documents. In most cases DOM represent the structure of XML and HTML documents.
* CSS - Allows you to define the presentation of a page such as fonts, colors, sizes, and positioning. CSS allow for a clear separation of the presentation from the content and may be changed programmatically by JavaScript.
Understanding the basic request/response nature of HTTP is also important. Many subtle bugs can result if you ignore the differences between the GET and OIst methods when configuring an XMLHttpRequest and HTTP response codes when processing callbacks.
JavaScript is the client-side glue, in a sense. JavaScript is used to create the XMLHttpRequest Object and trigger the asynchronous call. JavaScript is used to parse the returned content.
16 :: What exactly is the W3C DOM?
The W3C Document Object Model (DOM) is defined by the W3C as the following: The Document Object Model is a platform- and language-neutral interface.17 :: What is the difference between proxied and proxyless calls in AJAX?
Proxied calls are made through stub objects that mimic your PHP classes on the JavaScript side in AJAX. E.g., the helloworld class from the Hello World example.Proxyless calls are made using utility JavaScript functions like HTML_AJAX.replace() and HTML_AJAX.append() in AJAX.
18 :: What is the minimum version of PHP that needs to be running in order to use HTML_AJAX?
The oldest PHP version we've fully tested HTML_AJAX is 4.3.11, but it should run on 4.2.0 without any problems. (Testing reports from PHP versions older then 4.3.11 would be appreciated.)19 :: What is the XMLHttpRequest object in AJAX?
It offers a non-blocking way for JavaScript to communicate back to the web server to update only part of the web page.20 :: What JavaScript libraries and frameworks are available for AJAX support?
There are many libraries/frameworks out there (and many more emerging) that will help abstract such things as all the nasty browser differences. Three good libraries are The Dojo Toolkit, Prototype, and DWR.* The Dojo Toolkit contains APIs and widgets to support the development of rich web applications. Dojo contains an intelligent packaging system, UI effects, drag and drop APIs, widget APIs, event abstraction, client storage APIs, and AJAX interaction APIs. Dojo solves common usability issues such as support for dealing with the navigation such as the ability to detect the browser back button, the ability to support changes to the URL in the URL bar for bookmarking, and the ability to gracefully degrade when AJAX/JavaScript is not fully support on the client. Dojo is the Swiss Army Knife of JavaScript libraries. It provides the widest range of options in a single library and it does a very good job supporting new and older browsers.
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