I am trying to retrieve a json feed every 1 second. The URL that I am trying to retrieve displays JSON in the browser but will not be retrieved via a jquery getJSON
http://www.ridestreamline.com/Services/JSONPRelay.svc/GetMapVehiclePoints
function getBusLoc() {
$.getJSON('http://www.ridestreamline.com/Services/JSONPRelay.svc/GetMapVehiclePoints?callback=?', function(data) {
console.log(data);
setTimeout(getBusLoc, 1000);
})
}
getBusLoc()
It has something to do with the above link. What am I missing? Fiddle here
This is because of same origin policy, you can't sent ajax request from host A to host B, you can use jsonp instead (if your service supports this) , or if you has control to server side and you don't mind to old browsers you can use x-access-control-allow-origin http header in response to OPTIONS request (more info here https://developer.mozilla.org/en-US/docs/HTTP/Access_control_CORS)
Related
I'm trying to use window.fetch() to get json from the server, but can't get the data from the response.
I have this code:
let url =
'https://api.flightstats.com/flex/schedules/rest/v1/json/from/SYD/to/MEL/departing/2016/3/28?appId=f4b1b6c9&appKey=59bd8f0274f2ae88aebd2c1db7794f7f';
let request = new Request (url, {
method: 'GET',
mode: 'no-cors'
});
fetch(request)
.then(function(response){
console.log(response)
});
It seems that this request is successfull, I see status 200
and response body with json in network tab - status and response. But in console.log I dont see json object - console log image
I cant understand why I dont see json in console.log
The host site you are requesting from does not appear to support CORS. As such, you can't use fetch() to make a cross origin request and get the data back. If, you change your fetch() request to mode: 'cors', the debug console will show that the host site does not offer CORS headers to allow the browser to show you the result of the request.
When you are using mode: 'no-cors', the browser is hiding the result from you (because you don't have permission to see it) and you can see the response is tagged as opaque.
In a little poking around on the api.flightstats.com site, I did see that it supports JSONP which will allow you to work around the lack of CORS support issue and successfully complete a cross origin request.
For simplicity of showing that it can work, I used jQuery to just prove that a JSONP request can be made. Here's that code in a working snippet. Note I changed the URL from /json/ to /jsonp/ and specific dataType: "jsonp" in the jQuery request. This causes jQuery to add the callback=xxxxx query parameter and to fetch the response via that corresponding script (the JSONP method).
var url =
'https://api.flightstats.com/flex/schedules/rest/v1/jsonp/from/SYD/to/MEL/departing/2016/3/28?appId=f4b1b6c9&appKey=59bd8f0274f2ae88aebd2c1db7794f7f';
$.ajax(url, {dataType: "jsonp"}).then(function(response) {
log(response);
}, function(err) {
log("$.ajax() error:")
log(err);
})
<script src="http://files.the-friend-family.com/log.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
If you take a look at the documentation of the Fetch API; you'll notice that the API offers various methods to extract the data:
arrayBuffer()
blob()
json()
text()
formData()
Assuming the response is valid JSON (which I've noticed it doesn't seem to appear), you can use the response.json() function to retrieve the response data. This also uses a Promise mechanism, as for everything with the Fetch API.
response.json().then(function(data) {
console.log(data);
});
Setup is I have one Rails app setup to act as an JSON API and another static html page that I want to use to call the API. For sake of argument the rails API is at foo.com and the static html page is at bar.com.
On the foo.com app I have something like this:
if !cookies[:foo]
cookies[:foo] = "testing #{rand(500)}"
else
logger.info(cookies[:foo])
render :json => { :cookie => cookies[:foo] }
When I try to do a ajax GET request with jquery from bar.com the cookie does not get sent back to the JSON API.
$.get('http://foo.com/', function(data){console.log(data)})
But If I load the page a resource I can get the cookies to send back and forth between foo.com and bar.com
<script type="text/javascript" src="http://foo.com"></script>
Does anyone know why I am able to pass cookies back and forth cross-domain when loading the script as a script resource and not when I do a simple ajax request? Any way around this?
Use $.ajax as you need to make a JSONP request coz your ajax call is cross site.
$.ajax({
url: "xxxx",
crossDomain : true,
dataType : 'json',//if response is in JSON Notation
success : function (result){
alert(result);
}
});
Just as techie said, you need to use $.ajax and make a json(p) request in order for cross domain to be enabled.
Cookies are tricky with this sort of implementation though. even if you manage to send your cookies back and forth using some sort of hack, older (or cheaper) browsers will block them.
*cough* IE *cough*
A simple way to "hack" around this is to pass the cookie in the url, like so:
$.ajax({
url: "//domain.com/path/to/stuff;cookie1=value1?someParameter2=value2",
crossDomain : true,
dataType : 'json',//if response is in JSON Notation
success : function (result){
alert(result);
}
});
In this example, I've told my server that my request has a cookie name "cookie1" with a value of "value1" and a GET parameter with a value of "value2"
Hope this helps.
Here's the issue. I'm extracting gmail contacts through an ajax call in javascript/jquery like this:
function getUserInfo() {
var xml_parse = "";
$.ajax({
url: SCOPE + '?max-results=9999&access_token=' + acToken
data: null,
success: function (resp) {
xml_parse = $.parseXML(resp);
callGmailHelperWebService(xml_parse);
},
dataType: "jsonp"
});
}
function callGmailHelperWebService(xml_parse) {
GmailHelperService.ConvertXMLToList(xml_parse, onSuccess, onFailed, null);
}
So, as you can see, if the initial ajax call is successful, i call a function which calls a web service that sits on the save server as my project (in fact, it's part of the project).
My web service (GmailHelperService) is wired up correctly, as I can definitely call it in other places (like right after this ajax call, for example). However, when I try to call it within the "success" portion of the ajax call, i get the following error:
Uncaught Error: SECURITY_ERR: DOM Exception 18
My theory is that this has something to do with cross-domain issues, but I can't understand why. And I certainly can't figure out how to fix this.
I'd appreciate any help.
JSONP is a data transfer method that involves sending your data in this format:
callback({"foo":"bar"});
As you can see, this is NOT xml. It is JSON wrapped in a callback method that will get executed when the request is done loading, thus allowing it to be cross-domain because it can be requested using a <script> tag.
You cannot simply change your dataType to JSONP and return xml, expecting it to work. XML != JSONP. You can however return XML in jsonp, for example, callback({"xml","... xml string here "}) but be mindful of quotes, all json keys and values must be wrapped in double quotes, inner-quotes need to be handled appropriately.
If your request is a same domain request (Same protocol, same subdomain, same domain, and same port,) then you can change your dataType to "XML" if you are returning XML. Otherwise, you need to either setup a proxy script to get the xml for you, or have your webservice return JSONP.
For example, the following urls are all considered cross-domain from each other.
http://example.com
http://www.example.com
https://example.com
https://www.example.com
http://example.com:8080
All of the above urls would be considered cross-domain, even if they are on the same server.
So i have a json file named array.json on my web-server i intend to read this file in my web-application locally (for now) and then on a different domain once i go live, i have created this json file myself and here is the data it contains.
{"h1": "cmPanel", "h2" : "cmAuto", "h3": 0}
When i am trying to read the file I am not getting back a response, why would this be?
Here is my code for reading the file;
$.getJSON('http://www.foobar.com/array.json', function(data){
alert(data);
});
I have also tried adding &callback=? and still i receive nothing, could you please assist !
Quoting official docs:
Due to browser security restrictions, most "Ajax" requests are
subject to the same origin policy; the request can not successfully
retrieve data from a different domain, subdomain, or protocol.
Script and JSONP requests are not subject to the same origin
policy restrictions.
More info about Same Origin Policy
To work around it, look into JSONP.
In order to do cross-domain ajax calls you will either need to use a proxy or JSONP. Since you're setup for JSON already JSONP might be the easiest alternative. In short, JSONP entails wrapping your JSON data in a function call so it can be passed back to the calling script in a way that circumvents the Same Origin Policy.
In your case, you could wrap your json data with function named "myjsoncallback" so that it looks like this:
myjsoncallback({"h1": "cmPanel", "h2" : "cmAuto", "h3": 0})
And then change your ajax call to something like the following:
$.ajax({
url: 'http://www.foobar.com/array.json',
dataType: 'jsonp',
jsonpCallback: 'myjsoncallback', // Specify our callback function name
success: function(data) { console.log(data); }
});
Have you got access to the server from your web application? (same origin policy)
To use jsonp you could not simply add callback to the URL of the json file. The server should deliver a function that return the data. This file you could include with the default html script tag and execute the returned function afterwards.
To see the returned json you need to itterate the result
$.getJSON('array.json', function(data){
var items = [];
$.each(data, function(key, val) {
items.push('Key = ' + key + '<br/>Value = ' + val + '<br/><br/>');
});
alert(items.join(''));
});
array.json shoud be served with proper Content-Type:
text/javascript; charset=utf-8 if callback is used
application/json; charset=utf-8 if it is plain json
see here Best content type to serve JSONP?
to avoid problems from 'same origin policy'
I have a piece of javascript executing on a jetty server which is sending a XMLHTTPRequest to a scoket on another server(wamp server). The request gets sent to the socket, however the XHR response seems to be getting blocked.
I have heard that I can use JSONP to overcome this problem.
However as I am new to both javascript and I have never used JSONP technique before I would greatly appreciate any help in how to use this technique?
function sendPost(url, postdata, callback) {
xmlHttp=GetXmlHttpObject()
if (xmlHttp==null) {
alert ("Browser does not support HTTP Request")
return
}
xmlHttp.onreadystatechange=callback
xmlHttp.open("POST",url,true)
xmlHttp.send(postdata);
}
function sendInitRQ(width, height) {
var post = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><command type=\"init\"><width>" + width + "</width><height>" + height + "</height></command>";
sendPost("http://localhost:80/socket.php", post, initReturned);
}
I know that the php socket is recieving the post as when i check the server log i get a 200 on the get request.
I just want to know how can I use the JSONP approach?
I have seen exampples of the approach but Iam stilll unsure of how to do it.
The JSONP technique uses a completely different mechanism for issuing HTTP requests to a server and acting on the response. It requires cooperating code in the client page and on the server. The server must have a URL that responds to HTTP "GET" requests with a block of JSON wrapped in a function call. Thus, you can't just do JSONP transactions to any old server; it must be a server that explicitly provides the functionality.
The idea is that your client-side code creates a <script> block dynamically, with the "src" attribute set to the URL of the JSONP server. The URL should contain a parameter telling the server the name of the Javascript function you expect it to call with the JSON data. (Exactly what parameter name to use depends on the server; usually it's "callback", but I've seen some that use "jsonp".) The client must of course have that function in the global scope. In other words, if you have a function like
function handleJSON(json) {
var something = json.something;
// ... whatever ...
}
then your URL tells the server to call "handleJSON", and the server response should look like this:
handleJSON({"id": 102, "something": { "more": "data", "random": true }});
Thus when the <script> block is loaded from the "src" URL you gave, the browser will interpret the contents (the response from the server) and your function will be called.
It should be clear that you should only make JSONP requests to servers you trust, since they're sending back code to execute in your client, with access to any active session(s) your client has with other secured sites.
edit — Here's a nice article: http://www.ibm.com/developerworks/library/wa-aj-jsonp1/