Calling Web Service using XMLHTTP Object

Follow the steps to invoke a webservice using a XMLHTTP object in javascript

Step  1: Create a soap envelope for the requested method.

soapenvelope.gif

 var envelope = <The above string>;

Step 2: Create Instance of XMLHTTP Object

Now in the Javascript method create an instance of the XMLHTTP object

 xmlhttp.gif

 Step 3: Prepare the Webservice Request

 As shown above the url points the target webservice which is Service.asmx file and named of the method is HelloWorld. The syntax to be used

url1.gif
http://<Host Name>/<Virtual Directory>/<Webservice>/Method Name

in the next line we are initiating a POST request for the webservice url.

Step 4: Handling the Callback

callback.gif

Here when the response from the web service returns it just display the return string in alert box.

Step 5: Sending the  Request

 sendrequest1.gif

As shown above, the send message is send with the envelope  for the Web Method prepare in the Step 1.

Step 6: Executing the Web Service

calloutput.gif

Refer to this link for more  http://support.microsoft.com/default.aspx/kb/893659

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