AJAX is a contraction for Asynchronous JavaScript and XML. AJAX gives an ability to commune with the server asynchronously. At this point asynchronous is the keyword. To give details that in simple terms, you can propel a request to server and continue user communication with the user. You require not wait for response from the server. One time the response arrives, a designated area in UI will bring up to date itself and reflect the response information. entire page need not be reloaded.
This is accomplished by AJAX using XMLHttpRequest object. Your browser gives the capability for XMLHttpRequest object. Most contemporary browsers provide support for XMLHttpRequest. This object assists for http request and process XML response. It is not mandatory that you should make use of only XML. Easy text can also be used in Ajax but which is rare.
Before continuing with the more details we assume that we have basic knowledge about http headers, request response mechanism, diverse method types and response codes.
If you lack information in these areas, it is better to keep informed them before proceeding. If you can’t read GET, POST, HTTP status 200 OK and response Content-Type: text/html, xml then you must recognize these topics before learning AJAX. I am not writing in detail about them here, since each one of them calls for detailed separate information on topic.
Take an example of a HelloWorld ajax web application to show basics. We shall have a button with name ‘Say Hello!’ On click of that button, with no reloading the whole page we will display “Hello World!” by reinstating the ‘Say Hello!’ button. Going after source code listing contains total code of sample web application.
index.jsp
- <html xmlns=" url">
- <head>
- <title>Getting Started with AJAX In JAVA</title>
- <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
- <script type="text/javascript" language="javascript" src="ajax.js"></script>
- </head>
- <body>
- <div>Getting Started with AJAX In JAVA: Hello World!</div>
- <div id="hello"><button type="button" onclick="makeRequest()">Say Hello!</button></div>
- </body>
- </html>
Index.jsp holds a div ‘hello’. That is the div which XMLHttpRequest object is heading for overwrite with response from Servlet. On hit it off of the button we call a java script function makeRequest(). In anticipation of now, there is nothing special. Its customary jsp and javascript call. Ajax is not in the image.
At the present go through makeRequest() . Surrounded by that we call getXMLHttpRequest() which arrivals a XMLHttpRequest object. That can be used as a useful method in all your AJAX programs. Thats an endeavor to standardization. Different versions of browsers give different methods of creating XMLHttpRequest. We are covering all probable permutations inside that method.
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