October 10, 2011 06:49 by
Scottat this time I am going to look at Automatic Formatting in WCF 4.0.That is one of the great addition in WCF Web HTTP programming model(WCF RESTful). By using this feature it’s dynamically determine the format for the service operation. Previously, if consumed JSON and XML format for the same operation of the service then must have defined two different operations with explicitly annotated RequestFormat parameter of the WebGetAttribute and WebInvokeAttribute attributes.
For getting json format in WCF 3.5
[OperationContract]
[WebGet(RequestFormat = WebMessageFormat.Json)]
string GetJsonData();
For getting Xml format in WCF 3.5
[OperationContract]
[WebGet(RequestFormat = WebMessageFormat.Xml)]
string GetXmlData();
Now we have option either go with explicit as above or go with new automatic way .By default Automatic format selection is disable due to backwards compatibility and when it’s enabled, it would automatically get the best format in which to return the response. WCF infrastructure actually checks the type which is contained the request messages of Accept Header. The first priorities for media types, if it’s not found in Accept Header than its checks the content-type of the request message and if content-type would not give the suitable response than it would be used default format setting which is defined by RequestFormat parameter of the WebGetAttribute and WebInvokeAttribute attributes and at the last if there is no any default format setting than it would be used value of the DefaultOutgoingResponseFormat property.
1. Priorities of media types in request message’s Accept Header.
2. The content-type of the request message.
3. The default format setting in the operation.
4. The default format setting in the WebHttpBehavior.
Automatic format selection depends on AutomaticFormatSelectionEnabled property. It can be enabled programmatically or using configuration, for getting the clarification I would like to show example of it with Jquery, using jquery I will be getting the different format by calling the same operation of the service, for keeping it simple I am enabling the AutomaticFormatSelectionEnabled through standard endpoints, so let’s start it.
First I am going to create an empty web application JqueryWithWCF and hosting it at IIS.
I am going to add following items in the solution.
- WCFService item named RestfulService.svc
- html page named jqueryPage.htm
- jquery scripts file
We have to add System.ServiceModel.Web reference for working with WCF RESTful services.
Now let’s look at the IRestfulService.cs code
namespace WCFRestfulService
{
[ServiceContract]
public interface IrestfulService
{
[OperationContract]
[WebGet(UriTemplate = "/data")]
string GetData();
}
}
I added ServiceContract attribute at intrface to expose the service and OperationContract attribute for expose the operation out of the world ,now we have to add WebGet attribute with property name UriTemplate=”/data”, it means, it can be called using UriTemplate property name.
Look at the RestfulService.cs code
namespace WCFRestfulService
{
public class RestfulService : IrestfulService
{
public string GetData()
{
return "WCF 4.0 has introduced
a new property \"automaticFormatSelectionEnabled\"";
}
}
}
There is nothing special I did, just implemented IRestfulService interface and return a string.
Here is very key part for enabling the Automatic formate, we have Three different ways to enable the automaticFormatSelectionEnabled ,
1. Using Coding with ServiceHost object we can enable it.
2. Using webhttp behavior option
3. Using the standard endpoints
I am going with standard endpoints, because in standard endpoints we don’t need to configure each and every attribute , it has already configured the some attribute build in , so here is the configuration
As we can see in the above, I have commented behavior and serviceHostEnviroment tag, because we don’t need to service metadata and I have add the standard endpoint with “automaticFormatSelectionEnabled” attribute with value true.
That’s it, we have made a restful service and we can get the JSON or XML format by using single operation.
Now we have to put code at jqueryPage.htm page , here is the code of the page
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<style type="text/css">
ul{
border:1px solid black;
overflow:hidden;
width:270px;
}
li {
list-style-type:none;
float:left;
padding:5px;
}
</style>
<script src="Scripts/jquery-1.6.1.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(function () {
// javascript object for getting all the jquery objects
var pageElements = {
actionButton: $('#btnAction'),
xmlRadio: $('#rdoXml'),
jsonRadio: $('#rdoJson'),
xmlLabel: $('#lblGetXml'),
jsonLabel: $('#lblGetJson'),
isXML: true,
dataTypeValue: 'XML'
};
// set the button value on page load
SetButtonValue(pageElements.xmlRadio, pageElements.xmlLabel,
pageElements.actionButton);
//click event of xml radio button
pageElements.xmlRadio.bind('click', function () {
pageElements.isXML = true;
SetButtonValue(pageElements.xmlRadio, pageElements.xmlLabel,
pageElements.actionButton);
});
//click event for json radio button
pageElements.jsonRadio.bind('click', function () {
pageElements.isXML = false;
SetButtonValue(pageElements.jsonRadio, pageElements.jsonLabe
,
pageElements.actionButton);
});
//click event of the action button
pageElements.actionButton.bind('click', function () {
if (!pageElements.isXML) {
pageElements.dataTypeValue = 'JSON';
} else {
pageElements.dataTypeValue = 'XML';
}
//jquery ajax method for getting the result
$.ajax({
type: 'GET',
url: '/WCFRestfulService/RestfulService.svc/data',
contentType: 'application/json; charset=utf-8',
dataType: pageElements.dataTypeValue,
processdata: true,
success: function (msg) {
AjaxSuccess(msg, pageElements.isXML);
},
error: function (msg) {
alert(msg.error);
}
});
});
});
//it will call when the ajax hit successful
function AjaxSuccess(result,isXML) {
if (isXML) {
alert($(result).find('string').text());
} else {
alert(result);
}
}
//set button value on click on radio buttons
function SetButtonValue(elem,label,button) {
var buttonAction = $('#btnAction');
if (elem.is(':checked')) {
button.val(label.text());
}
}
</script>
</head>
<body>
<div>
<ul>
<li>
<input type="radio" name="rdobutton" id="rdoXml"
value="Get XML" checked="checked" /></li>
<li id="lblGetXml">Get XML</li>
<li>
<input type="radio" name="rdobutton" id="rdoJson"
value="Get JSON" /></li>
<li id="lblGetJson">Get JSON</li>
</ul>
<input type="button" id="btnAction" value="" />
</div>
</body>
</html>
I have created two radio buttons and a input button, when we hit the button it will call the jquery ajax method and check the pageElements.isXML Boolean value, if its false than JSON format called otherwise XML. For getting the proof i am using firebug, here is the result of firebug when we check radio button with Get XML and Get JSON.
I hope so you enjoyed the post . J