Skip to main content

AJAX-XMLHttpRequest Part2

(Link with the post AJAX-XMLHttpRequest 1)

First, need to know how to create an XMLHTTPRequest object.
With IE(The way of creating the object depend on the web browser), the request looks like:

http=new ActiveXObject("Microsoft XMLHTTP");

whereas in a standards-compliant browser object can be instantiated as:

http = new XMLHttpRequest();

Then an event handler which will be called via some event on user's page need to be written and it will handle sending the request for data to the server.

In the following example event handler called updateData ,a request of the server is made by using a GET method to an appropriate server-side script.A XMLHTTPRequest object has created and called it http:

function updateData(param) {

var myurl = [here I insert the URL to my server script];

http.open("GET", myurl , true); //This is to open the connection with the server.

http.onreadystatechange = useHttpResponse;

http.send(null);

}

http.open method: The Http request of the XMLHttpRequest object initialize through the open method. This method invoke prior to the actual sending of a request to validate the request method and URI user information to be used for the request. This method does not assure that the URL exists or the user information is correct.

The first parameter of the method is a string indicating the HTTP request method to use. It can be either a GET,POST,PUT,DELETE or HEAD.The second parameter of the method is another string, this one indicating the URL of the HTTP request.

The third parameter, a boolean value indicating whether or not the request will be asynchronousAn asynchronous request ("true") will not wait on a server response before continuing on with the execution of the current script. It will instead invoke the onreadystatechange evnt listner of the XMLHttpRequest object throughout the various stages of the request.

A synchronous request ("false") however will block execution of the current script until the request has been completed, thus not invoking the onreadystatechange event listener.

Comments

Popular posts from this blog

Convert an InputStream to XML

For that we can use DocumentBuilder class in java. By using the method parse(InputStream) ; A new DOM Document object will return. InputStream input; DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder parser = factory.newDocumentBuilder(); Document dc= parser.parse(input); In the above code segment,by using the created Document object,the corresponding XML file for the inputStream can be accessed. References: http://www.w3schools.com/dom/dom_intro.asp http:// download.oracle.com/javase/1.4.2/docs/api/javax/xml/parsers/DocumentBuilder.html

Concat two xml values with XSLT

The use-case described in this blog-post,is there's an WSO2 ESB node setup to proxy an incoming message to a particular back-end endpoint.  Before delivering the message to the back-end endpoint,from the ESB node itself,this incoming message need to processed and change its inside xml payload format. For eg: Below is the incoming message <?xml version="1.0" encoding="UTF-8"?> <CinemaHall name="liberty"> <OwnerData> <Name>John Smith</Name> <openedDate>12/12/80</openedDate> <quality>good</quality> </OwnerData> <CinemaHallData> <rows>100</rows> <seats> <seat>50</seat> <seat>60</seat> </seats> </CinemaHallData> </CinemaHall> This message need to be changed as  below; <?xml version="1.0" encoding="UTF-8"?> <CinemaHall name="liberty"...

CORS support from WSO2 API Manager 2.0.0

Cross-origin resource sharing (CORS) is a mechanism that allows restricted resources  on a web page to be requested from another domain outside the domain from which the first restricted resource was served. For example, an HTML page of a web application served from http://domain-a.com makes an <img src >  request for a different domain as 'domain-b.com' to get an image via an API request.  For security reasons, browsers restrict cross-origin HTTP requests initiated from within scripts as in above example and only allows to make HTTP requests to its own domain. To avoid this limitation modern browsers have been used CORS standard to allow cross domain requests. Modern browsers use CORS in an API container - such as  XMLHttpRequest  or Fetch - to mitigate risks of cross-origin HTTP requests.Thing to  note is it's not only sufficient that the browsers handle client side of cross-origin sharing,but also the servers f...