He was imprisoned during the persecutions of one of the Caesars. Peter and Paul were martyred during the first one, and Domitian's was the second - that is when John was exiled to Patmos.

Either way - it is obviously referring to future worldwide events that have not happened yet. Have all the seas turned to blood across the world? Has a 400 million man army come from China to fight against the antichrist? Is there a one-world leader and one-world church, where worship of the antichrist and his image is being enforced by beheading? Has there been a new temple built in Jerusalem? Have boils come upon everyone with the mark? Have all the armies of the world come against Jerusalem to wipe them out (battle of Armageddon)? Has the antichrist made a seven year peace treaty with Israel - and then defiled the temple/holy of holies in the middle of the seven years?

Pick any of the seals, trumpets, and vials - see what the book of Revelation has to say about them - then tell us they were fulfilled literally (and there is no prophetic fulfillment if it was not literal - all prophecies about Jesus' first coming were literal).