Javascript跨域Web服务调用

Question

I'm trying to call a .NET web service, from javascript, that returns an XML document. The web service is located on a different web server than my app. I do not have control over the web service. I have successfully called the service using jQuery setting the dataType to jsonp and I can see that the XML document is returned in Firebug. However, I get an error in the Firebug console "missing ; before statement" where it looks like it's trying to parse the returned xml (to json maybe??). Any ideas or what's the best way to call a cross domain web service that returns xml? Many Thanks!

Answer 1

The JSON-P data format is a JavaScript program. If you use JSON-P then the data you get back must be JavaScript.

JSON-P works by loading the document using a <script> element (and that is never going to work for arbitrary XML data)

Your options are:

1. Persuade whomever does control the web service to give you a JSON-P interface
2. Persuade whomever does control the web service to grant your site permission to access it via CORS (Note limited browser support )
3. Proxy the web service through your own server so your JS is operating on the same origin

Answer 2

Someting like this:

$.getJSON("http://yoursite.com/xml2json.php?callback=?",
  {feed:"http://agency.nd.edu/agencynd-team.xml"},
    function(data) {
      // process data here
    }
});

<?php
header('content-type: application/json; charset=utf-8');

if( strlen($_GET["feed"]) > 13 ) {
  $xml = file_get_contents(urldecode($_GET["feed"]));
  if($xml) {
    $data = @simplexml_load_string($xml, "SimpleXMLElement", LIBXML_NOCDATA);
    $json = json_encode($data);

    echo isset($_GET["callback"]) ? "{$_GET[’callback’]}($json)" : $json;
  }
}
?>

Answer 3

If you set dataType to jsonp you should get response wrapped in the function call. For example if you expect to get

object {"key": "value"} 

the response for jsonp should be

parseRespone({"key":"value"});

The reason for this is that jsonp adds <script> tag to your page header so it should append valid javascript code there.

If you have no possibility to contact with the developers of the server I would suggest to make ajax call to your page where the page would make curl connection to the .NET server and retrives the response in pure json.

Answer 4

One possibility is to avoid using JSON altogether and use cURL and a PHP proxy instead. Send the data to a PHP script on your server, which then forms a cURL session with the script on the other domain and returns to result to the original AJAX caller.