What has to be changed client-side or server-side to make getJSON() work?

I'm working with some web services that have already been created and I need to call them using ajax. The site I'm working on is hosted in a different domain than that of the web services. I'm now aware of the problems this causes with the same-origin policy.

I'm trying to get round it using JSON, based on articles:

JQuery API

IBM on cross-domain comms

and tonnes of other questions on here.

I have tried the following code (replaced actual domain with "webservice"):

    <script type="text/javascript">
          $(document).ready(function(){
        $.getJSON("http://webservice/restserver.aspx?",
        {
            method: "userInfo",
            userID: "039304303930302",
            sessionID: "STRING",
                format: "json"

        },
         function(data) {
                alert("GET Returned");
        });

});
</script>

1) Is there anything terribly wrong with this as I'm new to JSON and AJ开发者_Go百科AX

2) Does the web service need to have a callback e.g.- "&callback=?" added to it

3) Is there any other way to get around cross-domain calls

Any suggestions or help will be most welcome as I have working on this for ages.

Thanks!

You need JSONP which is different than JSON. You need to modify the web service method so that it can take an additional argument (for example callback=foo) and would wrap the JSON response in this function:

foo({ first_name: 'john', last_name: 'smith' })

Also to implement cross domain AJAX calls jQuery uses a hidden <script> tag so the web service must be configured to accept GET requests.

The $.getJSON() method documentation contains an example using Flickr which you could try running and looking at the exact request/response with FireBug. You may see it in action here.