How to call external webservice using jquery “jsonp”?

Question

I had a previous question can jquery ajax call external webservice?

and some good developers answered me to use jsonp, but i don\'t know how to use it, i am tr

Answer 1

You can't issue a POST request using JSONP, only GET (because <script src="..."> GETs the resource).

Answer 2

First you should add jsonp ('callback') in your web server like $_GET['callback']

Second ,don't forget the ';' after the output scripts

$data = '{"name" : "hello world"}';
echo $_GET['jsoncallback'] . '(' . $data . ');';

Now you can find out why the "missing ; before statement" problem occured.

html:

$.getJSON({"http://localhost:1096/MySite/WebService.asmx?callback=?",
        function(data){alert(data);}
        });

Answer 3

Hezil's code worked for me, but I had to change the server code to this:

$data = '{"name" : "hello world"}'; echo $_GET['callback'] . '(' . $data . ');';

Note the "callback" instead of "jsoncallback".

Answer 4

The point with JSONP is the P! P as in padding. You are padding the JSON object literal with a function call - invoking a function on the calling page taking the data object as an argument.

I.e. if you request the webservice, send the desired callback function name in the query string

...service/?callback=hello

Then the service should answer (using appropriate mime type):

hello({a: 17, b: 4117});

For a more in-depth explanation, see: http://www.stpe.se/2008/10/cross-site-data-retrieval-using-jsonp/

Answer 5

I've had a similiar problem, unfortunately I don't have the code at hand.

From memory:

• Add [ScriptService] as an attribute to your Web Method
• Also change your url to call the HelloWorld procedure.
  Something like http://localhost:1096/MySite/WebService.asmx/HelloWorld?callback

See: What are some good examples of JQuery using JSONP talking to .net? & What is the best way to call a .net webservice using jquery?