Can I use a "Direct Transit" Visa?

If I arrive via a cruise ship which disembarks from Hong Kong and has several port stops before reaching Shanghai (Taipei and Okinawa) and I spend only16 hours in Shanghai while the ship is docked there? And then travel on again to Japan? Also I have a multiple entry type issued in August of 2010 and I entered China only once prior to the "enter before" date...I can't tell if that is still valid? Is there an "expiration date"? Thank you!!