Cross origin problem when uploading file from visualforce page

Question

I am getting below problem when i try to upload a file on Google drive using save to drive button.

XMLHttpRequest cannot load https://ap1.salesforce.com/servlet/servlet.FileDownload?file=00P9000000jFRXN. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'https://c.ap1.visual.force.com' is therefore not allowed access.

How i can solve above problem using enable "CORS".

Answer 1

the issue can be addressed using the built-in HTTP(S) Proxy.

You can enable the proxy in the standard setup menu:

Setup -> Security Control -> Remote Sites / Remote Proxy Settings

Salesforce Setup Menu

There you can add your own salesforce instance. e.g. eu1.salesforce.com (don't forget to enable https)

In a second step you have to modify your ajax request:

var credential = ' OAuth ' + '{!GETSESSIONID()}'; // native VF function
var apiUrl = "https://na1.salesforce.com/services/data/v26.0/chatter/users/me";
$.ajax({
    type: "GET",
    // for community pages, use whole community url including path, e.g. 
    // https://logan.blitz01.t.force.com/customers/services/proxy.
    url: "https://c.na1.visual.force.com/services/proxy", 
    contentType: 'application/json',
    cache: false,
    success : function(response) {
                  alert("result" + response);
           },
    error : function(response) {
                  alert("Failed" + response);
           },                 
    dataType: "json",
    beforeSend: function(xhr) {
        xhr.setRequestHeader('SalesforceProxy-Endpoint', apiUrl);
        xhr.setRequestHeader("Authorization", credential);
        xhr.setRequestHeader('X-User-Agent', 'MyClient');
    }


});

Sources: https://trailhead.salesforce.com/modules/visualforce_fundamentals , https://gist.github.com/henriquez/3146782