How to post a file and parse an xml reply in Internet Explorer 7

I have written a web application that posts a file via http to a restful web service. The web service can reply with a 400 or 403 response if the service finds any problems with the request. The response also contains xml describing the reason(s) for replying with a http error code.

My web application posts the file to a hidden iFrame and uses the iFrame's onload event handler to execute a function that parses the server 开发者_如何学编程response presented in the iFrame and let's the user know how the file upload went.

My solution works great with firefox and chrome but not in internet explorer 7.

My problem is that if the server responds with an error code e.g. 400 or 403 internet explorer 7 loads its own static error page. This means that my script can't parse the error message sent in the response since the static error page is not from the same domain as the script itself and violates the same origin policy (and since it's a static error page the web service's detailed error message won't be there anyway).

I see only two workarounds to this problem and I would prefer to avoid them both if possible:

A) Have the web service return 200, when the user-agent indicates internet explorer, even though an error has occured but include a xml response that indicates an error.

B) Have the web application post to an "intermediary" that forwards the request to the web service, reads the response and then translates it to a 200 or anything else that works (so it's basically option A but more flexible and at least this keeps the restful web service "clean").

Is there another way to solve my problem?

Assuming you have control of the server, you may find the best solution is to use the iframe only for sending the file (i.e. one way....client to server). Then use an ajax polling solution to determine whether or not the post was successful. It can be a bit messy, but should be much more reliable, and you can also get information back before the post is complete.

I managed to solve this since a colleague remembered that if the response body is not of a certain length when sending a 4xx response, Internet Explorer will load its static error page.

The workaround is to send back a longer response body with your 4xx response, e.g. a xml-comment containing white space.