<p>In GWT I have to specify what locales are supported in my application. The code get compiled in various files, one for each locale (beside other versions), but I have to give my clients one only URL. This URL is supposed to be a page that should be displayed according to the locale preferred by the browser.
I dont't want to have an HTTP parameter for the locale since I want to forse the locale preferred by the browser.
How can this be coded in GWT?</p>

<p>Should I try to to this using apache rewrite rules? I thied it, but I think I cannot access such parameter easely in a rewrite rule.</p>

<p>Thanks a lot,
Giuseppe</p>

Unless I am reading the documentation incorrectly I don't think you have to do anything.
GWT and Locale
By making locale a client property, the standard startup process in gwt.js  chooses the appropriate localized version of an application, providing ease of use (it's easier than it might sound!), optimized performance, and minimum script size.
The way I read it, as long as your module has added all the locale choices to it, it should be automatic?