This link gives a pretty good explanation of how Struts handles i18n. The only thing it fails to mention is that in order to
test different languages, you have to change the language setting in your browser. In Internet Explorer, this is done by:
1-Select Tools-->Internet Options from the menu
2-Click the "General" tab and then the "Languages" button.
3-Add any number of languages with the "Add" button, but make sure the language you want to test is at the top of the list.
This process is pretty similar for other browsers.