A group of men armed with hammers and baseball bats entered McConnell's bar on Main Street at about 18:00 GMT on Wednesday and assaulted the man before driving off in waiting cars.
He was taken to hospital and is being treated for serious but non-life threatening injuries.
Six men, aged between 24 and 38, were arrested during follow-up searches.
Police appealed to anyone who witnessed the attack or who saw the group of men in the area to contact them.
A man in his 40s has been attacked by an armed gang at a bar in Doagh, County Antrim.