A321 pilot reported a near miss on the ground while taxiing to the gate when a ground vehicle crossed in front of the aircraft.

Narrative

Flight was complete ; taxiing to the gate of arrival XX. Upon receiving clearance to enter ramp area and cleared to taxi to the gate. We continued taxiing into position but held short of safety area while marshaling personnel did FOD check and positioned themselves. Once they were in position and cleared to proceed signals were given; we began moving. All of a sudden a service vehicle drove right in front of the moving aircraft causing the Captain to make an aggressive abrupt stop. The truck was so close to the nose that both flight crew; captain and first officer; as well as an FAA jumpseat occupant lost view of the truck under the nose until it passed onto the right side of the aircraft. This was agreed by all crew members as a near miss" event. Once the truck was clear and marshalers still in position; we continued taxiing to the gate.Cause: Marshaling crew could be tasked with walking further than the safety area and actually blocking traffic on the service vehicle path once aircraft is ready to move."