Having trouble retrieving JSON with crossDomain jQuery AJAX

The process I followed was creating a rails 3.0 scaffold and exposing it using json, keeping it running.

When accessing http://localhost:3001/objects.json

I can view json data in the browser

Next, I had a simple html file with code.jquery.com/jquery-1.7.min.js included. Opening this page in Firefox (Ubuntu), then opening the firebug console, I attempted the following:

var myurl = 'http://localhost:3001/objects.json';

$.ajax({
url: myurl,
dataType: 'jsonp',
error: function(data){ console.log("error:"+data); console.log("error:"+data.readyState); },
success: function(data){ console.log("success:"+data); }
});

The goal was to fetch the same json in the success handler. What I have noticed so far is:

If I specify dataType as 'jsonp'

  1. I receive the json response (verified in firebug:Net), identical to what I see in the browser
  2. The success function is not triggered
  3. The error function is called, with status code = 4, and status = "success"

Otherwise, I get

A blank response

Additionally, I consistently receive a 200 status code back.

Any clues on what could be happening here?

Below is my server-side code and log information

Code snippet =>

# GET /objects
# GET /objects.json
def index
  @objects = Object.all

  respond_to do |format|
    format.html # index.html.erb
    format.json  {
      render :json => @objects.to_json, :layout => nil
      }
  end
end

Sample of the log =>

Started GET "/objects.json?callback=jQuery17024293556233345082_1321347517236&_=1321347853199" for 127.0.0.1 at 2011-11-15 14:34:13 +0530
  Processing by objectsController#index as JSON
  Parameters: {"callback"=>"jQuery17024293556233345082_1321347517236",     "_"=>"1321347853199"}
  [1m[35mobject Load (0.1ms)[0m  SELECT `objects`.* FROM `objects`
Completed 200 OK in 11ms (Views: 5.4ms | ActiveRecord: 0.1ms)

Answer №1

In my opinion, utilizing $.getJSON could prove to be a more advantageous approach.

Answer №2

Perhaps the outcome you are receiving is due to an incorrect Content-type (not jsonp). If you wish for jQuery to trigger the 'success' event regardless of the Content-type, consider removing the dataType parameter from the ajax options.

Answer №3

My initial thought is that the correct syntax should be Object.all

It seems like the server you are requesting from is distinct from the one providing JSON data, possibly on different ports in this case. This indicates there may not be a necessity to use JSONP.

JSONP operates differently from Ajax as it utilizes the src attributes in script tags. For accessing information from the same server, consider using dataType: json.

If retrieving data from a separate server, it's recommended to append ?callback=? to the URL stream endpoint.

Using jQuery's $.getJSON method is advisable. For instance:


$.getJSON(url, data, function(response){<br>
// Process response;
        }); 

For more details, refer to http://api.jquery.com/jQuery.getJSON/

To address your recent query, utilize this structure.



$.getJSON("http://api.flickr.com/services/feeds/photos_public.gne?jsoncallback=?",
  {
    tags: "cat",
    tagmode: "any",
    format: "json"
  },
  function(data) {
    $.each(data.items, function(i,item){});

  });


Update I just recalled an essential point. If you manage both servers, are you sending JSONP responses? Consider this example of JSON data


response = { status:'success', message:'Successfully created object'}

To transmit it as JSONP, enclose it within a function(). Like so:


jsoncallback + "(" + JSON.stringify(response)  + ");";

This action executes Jquery-generated function internally (done when specifying callback=?) and passes your JSON data as parameters. It won't work if the server doesn't produce JSON-P responses.

Answer №4

There was a time in the past when we encountered a comparable problem, but it involved JSON rather than JSONP. Interestingly, it wasn't related to cross-domain issues. From what I remember, we had to eliminate respond_to from the controller and specify :status => 200 in the render method to resolve the issue. I can't guarantee this will work for you, but it's worth a try.

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