how to inject PersistentLocale for manage app locales ??

[Mohammad Shamsi]

i wrote this code to change locale, but i got NullPointerException, any idea
please?

public class Start {

    @Inject
    PersistentLocale locale;

    @PageAttached
    public void attached() {
        locale.set(Locale.GERMAN);
    }
}

-- 
sincerely yours
M. H. Shamsi