jQuery .ajax() POST Request throws 405 (Method Not Allowed) on RESTful WCF

I am sending a post request to a RESTFUL WCF service application. I am able to successfully send a POST request through Fiddler.

However when I do this through the jQuery Ajax method the function returns the following to the Chrome Developer Console:

OPTIONS http://www.example.com/testservice/service1.svc/GetData 405 (Method Not Allowed) jquery.min.js:6

But then a second after logs:

Object {d: "You entered 10"} testpost.html:16

What this tells me is that jQuery is sending a OPTIONS request, which fails, and then sending a POST request which returns the expected data.

My jQuery Code:

$.ajax() {        
type: "POST", //GET or POST or PUT or DELETE verb 
    url: "http://www.example.com/testservice/service1.svc/GetData", // Location of the service      
    data: '{"value":"10"}', //Data sent to server
    contentType:"application/json",
    dataType: "json", //Expected data format from server    
    processdata: false,
    success: function (msg) {//On Successfull service call   
        console.log(msg);
    },
    error: function (xhr) { console.log(xhr.responseText); } // When Service call fails             
});

I am using jQuery version 2.0.2.

Any help on why this error is occurring would be a great help.

Solution

Your code is actually attempting to make a Cross-domain (CORS) request, not an ordinary POST.

That is: Modern browsers will only allow Ajax calls to services in the same domain as the HTML page.

Example: A page in http://www.example.com/myPage.html can only directly request services that are in http://www.example.com, like http://www.example.com/testservice/etc. If the service is in other domain, the browser won't make the direct call (as you'd expect). Instead, it will try to make a CORS request.

To put it shortly, to perform a CORS request, your browser:

Will first send an OPTION request to the target URL
And then only if the server response to that OPTION contains the adequate headers (Access-Control-Allow-Origin is one of them) to allow the CORS request, the browse will perform the call (almost exactly the way it would if the HTML page was at the same domain).
- If the expected headers don't come, the browser simply gives up (like it did to you).

How to solve it? The simplest way is to enable CORS (enable the necessary headers) on the server.

If you don't have server-side access to it, you can mirror the web service from somewhere else, and then enable CORS there.