Trouble getting a valid response from a webservice

I am currently developing a web-frontend for a web service. I am using jQuery 1.5.1 as JS-Framework and Firebug for debugging purpose.

First of all, I have tested the web service with the Firefox Extension "REST Client". There, the following Request is successful:

{"requestUrl":"http://localhost:8080/Foobar/rest/goods?label=Schro","requestMethod":"GET","requestBody":"","headers":["accept","application/json"]}

Now, I want to reproduce this request in the context of a jQuery UI autocomplete() method:

$("#autocompleteTest").autocomplete({
    source: function( request, response ) {
        $.ajax({
            url: "http://localhost:8080/Foobar/rest/goods/",
            dataType: "json",
            data: {
                label: $("#autocompleteTest").val()
            },
            headers: {'accept':'application/json'},
            error: function(jqXHR, textStatus, errorThrown) {
                log(textStatus + "," + errorThrown);
                log(jqXHR);
            },
            success: function( data ) {
                console.log("bla:" + data);
                response( $.map( data, function( item ) {
                    return {
                        label: item.label + " # " + item.id,
                        value: item.id
                    }
                }));
            }               
        });
    },
       // [...]

I took this recipe from the jQuery UI autocomplete demo

However, this triggers the error-event. Firebug says:

GET http://localhost:8080/Foobar/rest/goods/?label=Schrott - 200 OK 16ms
Antwort-Header
Server  Foobar-Optimizer
Content-Type    application/json;charset=UTF-8
Transfer-Encoding   chunked
Date    Wed, 09 Mar 2011 10:50:03 GMT
Anfrage-Header
Host    localhost:8080
User-Agent  Mozilla/5.0 (Windows NT 6.1; WOW64; rv:2.0b12) Gecko/20100101 Firefox/4.0b12
Accept  application/json
Accept-Language de-de,de;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding gzip, deflate
Accept-Charset  ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive  115
Connection  keep-alive
Origin  null

The error jqXHR says:

[Object { readyState=0, status=0, statusText="error"}]

and the response Header is empty.

Both requests look identical in my eyes aside from the different results. I would appreciate any suggestions. Thank you.

Update: Solution

This is a cross-domain policy issue. I wasn't aware about this behaviour. The solution is to change the $.ajax datatype from "json" to "jsonp". This is an elegant method to override these policies and to access remote web-开发者_如何学JAVAservices.

Of course, the web service has to be able to handle this json "padding".

A bunch of other possibilities is mentioned here: http://usejquery.com/posts/9/the-jquery-cross-domain-ajax-guide

I can answer this question on my own: This is a cross-domain security policy issue. I wasn't aware of this behaviour.

The following link contains a bunch of applicable approaches:

http://usejquery.com/posts/9/the-jquery-cross-domain-ajax-guide