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Background Information
I am working on a web application that utilizes GWT (v2.4). For the application, I am creating an iframe that will display some information from another website. I need to access some information from that iframe that is normally restricted via the Same Origin Policy (SOP). However, both sites (the parent and iframe) are hosted on the same super-domain, just under different sub-domains. So, something like this:
I know the usual solution for this problem is to set the property: document.domain = 'mySite.com' on both parent and iframe site to allow passage of SOP. This works for all browsers (that I'm concerned with) except Internet Explorer 8 (and probably other versions).
The Problem
In IE, when I attempt to load my web application, I get a completely blank page with the following JS exception, "Access is denied." The source of this problem is in GWT's myGwtAppName.nochache.js where GWT generates some code during the compilation process that it needs (see below).
From the research I've done on this problem in general, the root cause of this issue seems to be that in IE, unlike all other browsers, iframes don't inherit their parent's document.domain settings. From what I understand, the code generated by GWT runs in an iframe (based on this comment: https://stackoverflow.com/a/5161888). So, what I think is happening based on my limited knowledge of JS:
The generated code that causes the exception
The below code, looks like it's setting up the GWT sandbox iframe environment.
var $intern_4 = 'myGwtAppName',
$intern_7 = 'body',
$intern_8 = 'iframe',
$intern_9 = 'javascript:""',
$intern_10 = 'position:absolute; width:0; height:0; border:none; left: -1000px; top: -1000px; !important',
$intern_11 = '<html><head><\/head><body><\/body><\/html>',
$intern_12 = 'script',
$intern_13 = 'javascript',
$intern_14 = 'var $wnd = window.parent;''
....
....
function setupInstallLocation(){
if (frameDoc) {
return;
}
var scriptFrame = $doc.createElement($intern_8);
scriptFrame.src = $intern_9;
scriptFrame.id = $intern_4;
scriptFrame.style.cssText = $intern_10;
scriptFrame.tabIndex = -1;
$doc.body.appendChild(scriptFrame);
frameDoc = scriptFrame.contentDocument;
if (!frameDoc) {
frameDoc = scriptFrame.contentWindow.document; //THIS CAUSES THE EXCEPTION
}
frameDoc.open();
frameDoc.write($intern_11);
frameDoc.close();
var frameDocbody = frameDoc.getElementsByTagName($intern_7)[0];
var script = frameDoc.createElement($intern_12);
script.language = $intern_13;
var temp = $intern_14;
script.text = temp;
frameDocbody.appendChild(script);
}
....
....
My Questions
Information Sources
IE doesn't inherit document.domain settings: https://stackoverflow.com/a/1888711 (and many other threads).
GWT runs in an iframe sand-box environment: https://stackoverflow.com/a/5161888
632
You may use html5 web messaging to communicate between iframe and parent.
Be aware that Internet Explorer has following bugs. You can send only string as messages. You can't send object like other browser support.
Some people advice to encode object into JSON if you wish to send more then just a string but sometimes it is cheaper to send URL encoded string just like query string in URL.
Here are examples 2 top results from my google http://tutorials.jenkov.com/html5/messaging.html https://thenewcircle.com/bookshelf/html5_tutorial/messaging.html
Take a look that they use different code to listen for messages
window.attachEvent("onmessage", handleMessage);
window.addEventListener("message", handleMessage, true);
First works with IE and old Opera and last works with a rest of world.
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