Russia needs China's help--especially financial--to develop the resources--including a potentially HUGE amount of crude oil--in eastern Siberia. The result is beneficial to both, since Russia will earn a lot of money from selling oil to China, and China won't need the enormous expense to shipping oil from the Middle East and Western Hemisphere since they could build overland pipelines from oilfields in eastern Siberia back to Chinese soil.
China copies everything from Russia.
The J-2 is a copy of the Mig-15
The J-5 is a copy of the Mig-17
The J-6 is a copy of the Mig-19
The J-7 is a copy of the Mig-21
The J-11 is a copy of the Su-27
The J-15 is a copy of the Su-33
The Chinese aircraft carrier Shi Lang is a Soviet Admiral Kuznetsov class aircraft carrier