I want to discuss a little about the Mig29K VS J15 debate.
Yes I understand why some people think it's better to just buy Mig29Ks for the Liaoning. In the case of this ship ALONE, I would say that this move MAY be a better option.
But China is a growing power and may even one day be on par with the U.S. in terms of economy. We need many carriers in order to protect our economic interests and of course for national security reasons. In the future we are going to build more carriers, and understandably they are going to be larger, better designed to suit the J15, or even have catapults on board. By then, the situation would be very very different.
The Liaoning need not to have maximized abilities. She's going to be a fully operational carrier for sure, but her most important role is to become a breeding bed, a training ship, the centre-piece around which China's CARRIER INDUSTRY develops. Smaller or less ambitious nations can just buy a carrier and an air-wing, but China, by nature and by will, can't. We need to develop a wholly independent carrier industry which comprises of carrier-building, dock-upgrades, high grade steel production, ship-borne nuclear reactors, radar systems and missile systems, steam catapults or even electric ones, home port construction, and many more. And one huge part of that system/industry is the carrier aircraft.
By designing and producing the J15, along with the development of the WS10 sea variant, it will enable China to enter the prestigious club of the few countries who can develop the whole carrier system, and most importantly, the amount of experience and expertise will allow us to make our own improvements upon it, and eventually develop future generation stealthy ship-borne aircrafts ourselves.
In fact if we take a look at China's military industry's developments, this decision is hardly surprising. Whenever possible China would want to pursue independence, but not blindly refusing any opportunity of foreign assistance or help. Whenever there's a chance for us to learn from others, we learn it, we buy it, and we analyze it and learn to make our own. It happened with the Su27/J11 aircrafts, it happened with the GT25000/QC280 steam turbines, it happened with the CFM56 core/WS10 engines, it happened with the Lavi/J10, it also happened with the Falcon/KJ2000 AWACS. Some may call this copying, or to put it nicely, reverse engineering. But I think it's the fastest way to develop. Learn from successful ones, and improve on it, finally we use these knowledge to develop our own. The J20, J31, WS15, KJ200, KJ500, QC185, 052C/D, are all such examples.