Stopover of 4.5 hrs

I'm flying from london to australia, with a stopover of only 4.5 hours in shanghai, so by the time I get into the city I'll probably only have an hour. I'm not staying in a hotel, do I still have to register with the police station for such a short stop, or is it registered with the airport that i'll leave in under 24 hours? If I still do have to register at a police station, do you have an estimated time that you think it'd take?