Q:

Check the file existence on the client side of GWT

I want to check the file existence of the client side of GWT, by using FileUpload and FormPanel. Since it is not possible to use java.io.File on the client side, does anybody know how to do this?
Thanks in advance!
Ike

A:

It is not possible to check in javascript in the browser, whether a file exists or not. A file upload form does not give you the path to the file it is uploading (otherwise, it'd be a security hole!). 
There is no reason why the browser needs to check the client side's file system.
An alternative would be either to use a java applet, and get the appropriate certificates/user permission so that it can read off disk, or some such browser plugin that also can perform disk reads (read: activeX plugins for IE)

