Some Chinese cuisine might look vegetarian, but the tofu and string beans have likely been enriched with pork fat. Meat is often the stock of sauces.
If you’re at a Chinese restaurant in Shanghai, clearly explain to the staff ‘wo chi shu’ (I’m a vegetarian). If you are then served a dish with meat, politely send it back immediately without paying. Shanghai has a growing number of vegetarian restaurants that use tofu to imitate meat. There are plenty of Western restaurants that serve traditional vegetarian standbys such as pizza, pasta and salad. Food shopping is not a problem for vegetarians. Local and international supermarkets are usually well-stocked with a variety of vegetables, and cooks will be more than happy with the variety of soy products.