Consuming CurrencyConverter web service through JavaScript

Hi,

For getting the currency conversion rate we could use the following web service provided by Generic Objects Technologies Ltd.

Check out the web services provided by them

http://www.webservicex.net/WCF/webServices.aspx

To consume their currency converter web service

http://www.webservicex.net/CurrencyConvertor.asmx we could use the following JavaScript code

var xmlHttp;
function SoapCall() {
// creatng the xmlHttp object
xmlHttp = new ActiveXObject(“Microsoft.XMLHTTP”);
// Calling the web service using post and true means asynchronous call
xmlHttp.open(“post”, “http://www.webservicex.net/CurrencyConvertor.asmx”, false);
// Setting the request header to let the web service identify the soap request we would be sending

xmlHttp.setRequestHeader(“Content-Type”, “text/xml; charset=utf-8”);

xmlHttp.setRequestHeader(“SOAPAction”, “http://www.webserviceX.NET/ConversionRate”);

var soapRequest = “<?xml version=’1.0′ encoding=’utf-8′?> ” +
“<soap12:Envelope xmlns:xsi=’http://www.w3.org/2001/XMLSchema-instance&#8217; xmlns:xsd=’http://www.w3.org/2001/XMLSchema&#8217; xmlns:soap12=’http://www.w3.org/2003/05/soap-envelope’>&#8221; +
” <soap12:Body>” +
”   <ConversionRate xmlns=’http://www.webserviceX.NET/’>&#8221; +
”     <FromCurrency>USD</FromCurrency>” +
”    <ToCurrency>INR</ToCurrency>” +
”  </ConversionRate>” +
“</soap12:Body>” +
“</soap12:Envelope>”;

xmlHttp.send(soapRequest);
alert(xmlHttp.responseText);

}


Bye..

Understanding and Using AJAX

Suppose this is our simple ASP.NET page i.e. MyPage.aspx which would be called using AJAX

Code for MyPage.aspx.cs

protected void Page_Load(object sender, EventArgs e)

{

// no data is passed

if (Request.QueryString[“myGetData”] == null)

{

Response.Write(“Hello World”);

}

// if GET method is used to call this page

else if (Request.QueryString[“myGetData”] != null)

{

Response.Write(“Hello “ + Request.QueryString[“name”].ToString());

}

// if POST method is used to call this page

else if (Request.Form[“myPostData”] != null)

{

Response.Write(“My Post Data is “ + Request.Form[“myPostData”].ToString());

}

}

Delete everything from MyPage.aspx page just keep the page directive otherwise html tags would also be sent as a part of response.

<%@ Page Language=”C#” AutoEventWireup=”true” CodeFile=”Mypage.aspx.cs” Inherits=”MyPage” %>

Now the javascript code to call the page asynchronously using AJAX. Comment/Uncomment the particular section of code to test the functionality

<script type=”text/javascript”>

var request=null;

function CreateRequest()

{

try

{

// create a new object to talk HTTP with a web server.

// XMLHttpRequest – works on Safari,Firefox, Mozilla, Opera , IE 7 and most other browsers

request=new XMLHttpRequest();

}

catch(trymicrosoft)

{

try

{

// Msxml2.XMLHTTP – Most version of IE support this

request=new ActiveXObject(“Msxml2.XMLHTTP”);

}

catch(othermicrosoft)

{

try

{

//Microsoft.XMLHTTP – but for some, we’ll need this other type

request=new ActiveXObject(“Microsoft.XMLHTTP”);

}

catch(failed)

{

request=null;

}

}

}

if(request==null)

alert(‘Error creating request object’);

else

{

// i.e. space with %20

// if no data is to be send

var url=“MyPage.aspx”;

// open-initialize the connection

// GET – specify how to send data to the server

// url- url to send the request

// asynchrounous – true

request.open(“GET”,url,true);

// telling the browser what to do with the server’s response

// i.e. the function to be called when response is received

// onreadystatechange- this property affects every ready state not just the one indicating

// that the server is finished with request

request.onreadystatechange=updatepage;

// send the request

// no data is required so send null

// for using send() to pass data to a server requires POST method for the request and need to specify content type

request.send(null);

// if data is to be send using GET i.e. as query string

var name=“MyName”;

// escape() function replaces characters like space with something that will work as a part of a request URL.

var url=“MyPage.aspx?myGetData=”+escape(name);

request.open(“GET”,url,true);

request.onreadystatechange=updatepage;

request.send(null);

// if more data is to be send than use post

var name=“MyName”;

var url=“MyPage.aspx”;

request.open(“POST”,url,true);

request.onreadystatechange=updatepage;

//setRequestHeader()- allows us to add information to the request usual intended for use by the server

// Content-Type – is the name of the request header

// application/x-www-form-urlencoded – the value of the request header

// this tells the server that the data is encoded like it would be in a request URL

// for passing XML content replace “application/x-www-form-urlencoded” with “text\xml”

request.setRequestHeader(“Content-Type”,“application/x-www-form-urlencoded”);

// specify the data to be send

// escape() function replaces characters like space with something that will work as a part of a request URL.

request.send(“myPostData=”+escape(name));

}

}

// updatepage – this function will get run every time the ready state changes

function updatepage()

{

// readyState=this property of the request object stores the current state

// if 4 means server is done with the request

// if 0 i.e uninitialized

// if 1 i.e open, the object has been created but the send method has not been called

// if 2 i.e. sent, the send method has been called.

// if 3 i.e. receiving , responseText is not available but some data has been received

// if 4 i.e. loaded, all the data has been received, responseText is available

if(request.readyState==4)

{

// check for the status send by the server

// if 200 i.e. everything is fine

// if 404 i.e. if the page specified in the url is not found

if(request.status==200)

{

var myResponse=request.responseText;

alert(myResponse);

}

else

{

alert(“Error! Request status is “ +request.status);

}

}

}

</script>

<input id=”Button1″ type=”button” value=”button” onclick=”CreateRequest()”/>

Bye…

Calling Asp.NET web service from javascript (Ajax)

Here we will be calling the default helloworld webservice that is already created for us when we open a asp.net webservice project template in Visual Studio.

We’ll just have a textbox(html control) which will display us the Hello World! response returned from the web service.

This is the step we need to follow

1) Create a new ASP.NET WebApplication

2) Put a html textbox control on the form

<input type=”text” id=”info”/>

3) Put this script code in the head section of the aspx page

<script language=”javascript”>

var xmlHttp;

function getMessage()

{

xmlHttp=new ActiveXObject(“Microsoft.XMLHTTP”);

xmlHttp.open(“post”, “http://localhost/WebService1/Service1.asmx/HelloWorld&#8221;, false);

xmlHttp.onreadystatechange=doUpdate;

xmlHttp.send();

return false;

}

function doUpdate()

{

if(xmlHttp.readyState==4)

{

var startTag = “<string xmlns=\”http://tempuri.org/\”>”;

var endTag = “</string>”;

var exch;

var valueStart = 0;

var valueEnd = 0;

valueStart = xmlHttp.responseXML.xml.indexOf(startTag, valueEnd) + startTag.length;

valueEnd = xmlHttp.responseXml.xml.indexOf(endTag, valueEnd+1);

exch = xmlHttp.responseXML.xml.substring(valueStart, valueEnd);

document.forms[0].elements[‘Info’].value=exch;

}

</script>

4) Call the getMessage function in the body’s onLoad eventHandler

<BODY onload=”getMessage()”>

5) Run the applicaton. We’ll see the HelloWorld! text in our textbox(‘info’)

Now let us understand what is happening inside the javascript code

xmlHttp=new ActiveXObject(“Microsoft.XMLHTTP”)

This line of code creates the XMLHttpRequest object. This object sends request to the server and processes the responses from it.

The above code creates the object specific to Internet Explorer( <=6.o).

It is implemented as Active X for IE. However in IE 7 XMLHttpRequest will come as native JavaScript object.

For other browsers we can write

xmlHttp=new XMLHttpRequest();

or best we can write this

if(window.ActiveXObject)

{

xmlHttp=new ActiveXObject(“Microsoft.XMLHTTP”);

}

else if (window.XmlHttpRequest)

{

xmlHttp=new XMLHttpRequest();

}

xmlHttp.open(“post”, “http://localhost/WebService1/Service1.asmx/HelloWorld&#8221;, false);

The open method initializes the connection to the server and informs the xmlHttp object how to connect to the server.

post- it indicates how we want to send the data. It can be “get” as well

url- comes the url where we are connecting

false- this means we are making a synchronous call. To make asychronous call simply set it to true

xmlHttp.onreadystatechange=doUpdate;

This specifies the name of the function to be called whenever the state of the xmlHttpRequest changes

xmlHttp.send();

Send method than makes the request to server. This method would return immediately in case of asynchronous call and it would block until the synchronous response is received from the server.

if(xmlHttp.readyState==4)

It tells about the current state of the request

0- uninitialized

1- loading

2- loaded

3-interactive

4-complete

xmlHttp.responseXML.xml

It returns the current response from server in XML=

<?xml version=”1.0″?>

<string xmlns=”http://tempuri.org/”>Hello World !</string>

Than we are using some javascript functions to get the Hello World! and remove everything else.

document.forms[0].elements[‘Info’].value=exch;

Finally assigning the value to our textBox.

The function doUpdate() can be written differently so that we don’t have to make use of any string functions.

function doUpdate()

{

if(xmlHttp.readyState==4)

{

// Here the server is returning us XML in response so we can make use of responseXML

// Here the browser creates a DOM tree to represent that XML and puts a reference to that DOM tree

// in the request’s (xmlHttp) object’s responseXML

var xmlDoc=xmlHttp.responseXML;

var responseElement=xmlDoc.getElementsByTagName(“string”)[0];

var respText=responseElement.firstChild.nodeValue;

document.forms[0].elements[‘Info’].value=respText;

}

 

However creating a ASP.NET AJAX webservice is little different than our normal ASP.NET web service, and calling them using the ASP.NET AJAX client library is also a bit different

https://nishantrana.wordpress.com/2007/11/06/creating-and-calling-aspnet-ajax-web-service/

Bye