China will buy (license) military technology when it can, but because China is a police state, and often acts like one even to outsiders, most Western military technology is unavailable for license. So China steals it, or buys it in secret. Often China will steal the technology even when it is available for sale. China has been doing this to Russia for decades, and was recently forced, by Russian threats of legal and diplomatic action, to sign an agreement promising to stop the technology theft. It won't, but the agreement will make it more costly for China when they get caught in the future and the Russian lawyers come after them.
China regularly plunders military technology wherever it can find it. South Africa is a recent target. For example, last year, China offered for export sale an air-to-air missile similar to the U.S. AIM-9X, and the South African A-Darter. The Chinese had tried to buy the A-Darter technology, and some serious negotiations ensued (during which Chinese engineers got a close look at the A-Darter), but the deal fell through in 2001. Now the Chinese are selling what appears to be a clone of the A-Darter. Coincidence? Not likely, if you take a look at the Chinese track record.
For example, China has been trying to develop a helicopter gunship; the Z10, for over a decade. Eight prototypes have been built so far. Despite the Western arms embargo on China since 1989 (because of the Tiananmen Square massacre), the Z10 is powered by a Canadian engine (two Pratt & Whitney Canada PT6C-67Cs). The Canadian firm says it sold the engines to China with the understanding that they were for a new civilian transport helicopter.
Development of the Z-10 began during the early 1990s. China approached helicopter gunship manufacturers in South Africa and Italy for technical assistance. The South Africans turned them down in 2001, because all the Chinese apparently wanted was to buy a single Rooivalk gunship. The manufacturer, Denel, refused, realizing that the Chinese, as they have so often done in the past, simply wanted to reverse engineer elements of the Rooivalk, without paying for any technology used. South African firms has since uncovered evidence of China stealing technology for South African missiles, electronics and artillery.
Pratt & Whitney Canada will not sell any more engines to China, which means that the Z-10 cannot enter mass production until China develops a suitable replacement for the PT6C-67C engine. That might take a few years, at least. Until recently, China refused to release any information about the Z-10, but for the last few years, there have been increasing rumors of Western firms secretly assisting in the gunship's development. The Z-10 appears to be similar to the Agusta/Westland A129, or the upgraded versions of the U.S. AH-1 (especially the AH-1 SuperCobra). The 4.6 ton A-129 was the first helicopter gunship designed and built in Western Europe, and was introduced in the 1980s. The Z10 appears to have a FLIR (night vision device), radar and is armed with a 23mm autocannon and hard points for up to eight missiles or a larger number of unguided rockets. The Z10 is a Western style gunship. The only gunships the Chinese had previously were Russian designs. But even the Russians have since adopted the Western style, as pioneered with the AH-1. China has been developing its own helicopter for several decades. First they used helicopters and technical assistance from Russia, but for the last two decades, most of the tech has come from Europe.
China is pretty blatant about its technology theft, especially when it comes to weapons. When accused, they deny everything. So far, that works. But as China tries to export more weapons containing purloined technology, they are finding themselves meeting more angry lawyers, than eager buyers.