java - Sending JSONP vs. JSON data?

Question

I am making a web service that needs to return data in JSONP format. I am using the JSON taglib for JSP, and I thought all that had to be added were parenthesis, but I cannot find a good resource which verifies this.

For example, ever web service function returns using this function:

private static String getJSONPObject(String s) throws JSONException {
    return "(" + new JSONObject(s) + ")";
}

Is this correct?

Thanks!

Answer 1

JSONP is simply a hack to allow web apps to retrieve data across domains. It could be said that it violates the Same Origin Policy (SOP). The way it works is by using Javascript to insert a "script" element into your page. Therefore, you need a callback function. If you didn't have one, your Javascript would have no way to access the JSON object. But by using JSONP, your Javascript code can call the callback function.

So you must specify the callback name. So your function might look like this:

private static String getJSONPObject(String callback, String s) throws JSONException {
    return callback + "(" + new JSONObject(s) + ")";
}