I use UTF8 on helma, everything is fine. I can post chinese on antville very well. But after restart helma, all the chinese char. become ????. Any idea about this bug? How it comes?

Probably your database does not support Unicode. Helma handles Unicode well (by adding

charset = UTF-8

in the server.properties or apps/antville/app.properties file, which you did, I suppose). Obviously, Unicode text is ok as long as it's cached inside Helma, but when restarted it's fetched from DB.

What database are you using? I think productino versions of MySQL do not really support Unicode at this time. With Mckoi and many other database products you should be ok.