Is a visa necessary to transit China to Japan, am a Ugandan?

I'm a Ugandan passport holder, and planning to go to Japan via China. I heard a visa isn't required for 2-hours transition in China, but I will stay for 4 hours. The below is an example.
CZ4619 L 06OCT EBB　NBO 0900 1010 06OCT
CZ6044 L 06OCT NBO　CAN 1250 0945 07OCT
CZ 379 L 07OCT CAN　NGO 1400 2115 07OCT

Do I have to get a Chinese visa? If so, what type?