An A319 experienced severe turbulence on descent into DEN; followed by wake turbulence behind a B777 on final.

Narrative

We had been cleared directly to TOMSN intersection for the TOMSN STAR into DEN. We had been at FL310 where we experienced continuous light chop/turbulence; which we reported to DEN Center. DEN Center then cleared us to FL290 and informed us that continuous light turbulence/ occasional moderate chop could be expected on the STAR. Passengers were seated at the initial onset of light chop/turbulence at FL310. We informed the flight attendants about the expected turbulence on the descent into DEN and asked them to put things away. The flight attendants called us when they had everything put away. After descending to FL290; we were experiencing light turbulence; so we seated the flight attendants. Approximately 60 miles west of TOMSN; we experienced moderate turbulence; followed by 2 jolts of severe turbulence; during which the aircraft banked +/- 30 degrees of bank (uncommanded) and the airspeed instantaneously increased approximately 20 knots. We experienced about a 5 knot overspeed at that point and received an overspeed ECAM. As the PF; I disconnected the auto-pilot and auto-throttle to slow the aircraft down. As soon as the aircraft was slowed; we initiated a descent. No further severe turbulence was experienced on our arrival into DEN. We contacted the flight attendants shortly thereafter and they answered our query about everyone being okay with 'everyone is still seated and everyone is OK.' We believe that no injuries occurred during this severe turbulence encounter. We continued our descent into DEN via the TOMSN STAR. Much virga was present and we received deviation vectors around the virga. On final approach to Runway 16R; we were informed that we were following a B777 approximately 7 miles ahead of us. The winds were very erratic down final; with mostly a slight tailwind. At about 1000 feet AGL; the winds were actually swirling. We were about a dot high on the glideslope to avoid any possible wake turbulence. With the erratic winds; we were still experiencing some slight wake turbulence from the preceding B777. I elected to stay high on the glideslope; which resulted in a slightly long touchdown on the runway. This was discussed with my copilot during the event. Landing and parking were uneventful.