The locale used to process requests and events is, by default, determined by the browser's preferences (by use of the getLocale method of javax.servlet.ServletRequest).

However, it is configurable. For example, you might want to use the same Locale for all users no matter how the browser is configured. Another example is that you might want to use the preferred locale that a user specified in his or her profile, if you maintain the user profiles in the server.