China has long kept older warplanes in service, even though they have become obsolete. Currently, the Chinese fighter force consists of nearly 500 modern aircraft (J-10s, J-11s, Su-30s), 500 J-7 (equivalent to the MiG-21), 300 J-6 (equivalent to the MiG-19), 200 J-8 (a twin engine MiG-21 variant), and 300 Q-5 (a MiG-19 variant). The older models (the MiG-19 is a 1950s design) are being phased out, either because more modern aircraft enter service, or the older ones are just worn out (even though they do not fly, for training, nearly as much as Western aircraft.)
But the Chinese believe some of their older designs still have lots of useful life left. In particular, they are revamping many of their J-8s to be "smart" bombers. This is being done to take advantage of new smart bomb designs the Chinese are introducing. These include laser and satellite (GPS) guided bombs. The J-8II has had a hard point added under the fuselage, and additional ones on the wings. A new radar, equipped to support finding and hitting, ground targets has been added. The new J-8 model can deliver laser or GPS smart bombs.
The J-8 was a failed design (it's less maneuverable than the original MiG-21 it was based on), and maneuverability is further degraded when carrying all those bombs. But if the J-8II can deliver those smart bombs effectively, the new model will be considered a success. The J-8II is also being equipped for SEAD (Supression of Enemy Air Defenses), carrying anti-radiation missiles to destroy enemy radars.
China is also pushing its J-8 fighter for export sales. Another new model, the J-8T, has a more modern radar and has been shown carrying a reconnaissance/electronic warfare pod. The J-8II is also a prime export product, along with lots of those expensive new Chinese smart bombs.
The J-8 is an 18 ton, two engine, variant of the MiG-21. This was China's first attempt at building their own aircraft design. But it was not a very original or successful effort. The J-8 first flew in 1969, and didn't get into service until 1980. It was quickly realized that this was a turkey.
Fewer than 400 were built. The F-8 carries about three tons of bombs, and is not very maneuverable. China decided to make the most of it, and used the J-8 as a reconnaissance and electronic warfare aircraft. Thus the navy adopted it as well. It was a J-8 that collided with an American EP-3 reconnaissance aircraft off the coast in 2001. The J-8, which made the mistake of maneuvering too close to the much slower (propeller driven) EP-3, and crashed. The EP-3 survived and made an emergency landing in China, kicking off months of diplomatic tension.