How to get the current language from a webapp ?

Hi

I'm building a small webapp to display content extracted from a legacy 
database. Depending on the language of the page currently displayed by 
Jahia, labels and content should be customized to the same language.

It looks that 
org\jahia\services\applications\ServletIncludeRequestWrapper.java does 
set a few session values made available to web-apps running within Jahia 
as a portlet, but I can't see any that would give the information of the 
language of the current page.

Is there any other manner to get this language info ?

Thanks for your help