I agree with what's been said: it's a myth that your snake will become aggressive if you feed him in his enclosure, and it can even stress them out if you try to move them before and after feeding.

One thing that is really important is to be careful about feeding on loose substrate (aspen, coco husk, etc.) because if your prey item is damp or if your snake gets really excited about it, it's possible that your snake could ingest part of the substrate.

I used to keep mine on aspen and fed on it, but after a scare about aspen ingestion I moved him immediately onto strictly paper towels with no problems.