Class Ext.util.JSONP

Provides functionality to make cross-domain requests with JSONP (JSON with Padding). http://en.wikipedia.org/wiki/JSON#JSONP

Note that if you are retrieving data from a page that is in a domain that is NOT the same as the originating domain of the running page, you must use this class, because of the same origin policy.

The content passed back from a server resource requested by a JSONP requestmust be executable JavaScript source code because it is used as the source inside a <script> tag.

In order for the browser to process the returned data, the server must wrap the data object with a call to a callback function, the name of which is passed as a parameter callbackKey Below is a Java example for a servlet which returns data for either a ScriptTagProxy, or an HttpProxy depending on whether the callback name was passed:

boolean scriptTag = false;
String cb = request.getParameter("callback");
if (cb != null) {
    scriptTag = true;
    response.setContentType("text/javascript");
} else {
    response.setContentType("application/x-json");
}
Writer out = response.getWriter();
if (scriptTag) {
    out.write(cb + "(");
}
out.print(dataBlock.toJsonString());
if (scriptTag) {
    out.write(");");
}

Below is a PHP example to do the same thing:

$callback = $_REQUEST['callback'];

// Create the output object.
$output = array('a' => 'Apple', 'b' => 'Banana');

//start output
if ($callback) {
    header('Content-Type: text/javascript');
    echo $callback . '(' . json_encode($output) . ');';
} else {
    header('Content-Type: application/x-json');
    echo json_encode($output);
}

Below is the ASP.Net code to do the same thing:

String jsonString = "{success: true}";
String cb = Request.Params.Get("callback");
String responseString = "";
if (!String.IsNullOrEmpty(cb)) {
    responseString = cb + "(" + jsonString + ")";
} else {
    responseString = jsonString;
}
Response.Write(responseString);

This class is a singleton and cannot be created directly.