Why is the fail method being called from my jQuery.getJSON() method?

Question

I have a html page loaded directly from a local file in a web browser (FF 14.0.1 or Chromium, on Ubuntu 12.04)

The html page includes a local jQuery js file, and then includes a local js file with this method:

function start() {
     $.getJSON("http://localhost:8080/app/connect?callback=?", "id=11", function() { alert("win!"); })
     .done(function() { alert("done"); })
     .fail(function(xhr, request, error) { alert(xhr.status + "<> + request + "<>" + error); }); }

I'm responding to these requests from a JBoss / Restful web server with no special configuration, the method on the server is annotated with @Produces({"application/json"}). Server doesn't show any errors, even gets the id value correctly.

When I trigger this javascript, the fail method is called and I get this alert:

200<>parsererror<>jQuery311391951_513134 was not called

I can see the JSON response when inspecting with Firebug, it looks ok. In Chromium, I can inspect the request / response headers and everything looks ok. I have that text saved, if anyone thinks it might give more insight.

Can anyone tell me what's going on? Why do I get this error?

Thanks in advance!

Answer 1

It looks like you are accessing a local resource, in that case you don't have to use jsonp. You can remove the callback=? from the url.

It is used if you have to access a third party resource with Same Origin Policy violations

function start() {
    $.getJSON("http://localhost:8080/app/connect", "id=11", function() { 
        alert("win!");
    }).done(function() { 
        alert("done"); 
    }).fail(function(xhr, request, error) { 
        alert(xhr.status + "<>" + request + "<>" + error); 
    }); 
}

Answer 2

You are using JSONP (JSON with Padding). The server must unterstand the ?callback= Paramater and wrap the JSON answer with the callback function. This is mandatory for calls where SOP restrictions apply. If not (same domain and port) then remove the callback parameter.