Wait about 2 years?
Just kidding. Boxers are notorious for jumping up on people. It is in their nature. It takes time and proper training to get your boxer to refrain from this kind of greeting. Have you taken you pup to obedience classes? If not then it probably wouldn't be a bad idea. Manners are pretty important for a dog the size of a boxer. The best thing to do is to tell him "no" and "down" or wichever word you want to designate as the "get off of me" command.
Then ignore him until he calms down. Any attention you give him will only encourage him to keep jumping. In the case of visitors, just put him on a leash, or in his crate when company comes in and tell them to ignore him until he can calm down. There are about a million other things that you can do as far as training but I would suggest you contact a trainer or at least buy a good book on training dogs ( I think there may be a few recommended by this site).
