Sub-leasing

I’m going to be going back to the States for 6 months in August, at which point my lease is up on my apartment. Thing is, I really enjoy my spot, in terms of its location and price, and want to come back to it after Chinese New Year. I know I’d have to ask the landlord, but I’m wondering if it’s common for people to sublease their apartments for a space of time with plans to come back, as in my case. Has anyone here ever experienced sub-leasing, either being the sub-leaser or the sub-leasee (are those terms?). Would there have to be a contract drawn up between me and the new tenant or between the new tenant and the landlord? If anyone’s got any experience with doing this sort of thing, I’d greatly appreciate any advice. Thanks.