By Matt Smith DUBAI (Reuters) - Roger Federer's enduring class shone through again as the Swiss maestro beat world number one Novak Djokovic 6-3 7-5 to win the Dubai Championships for a seventh time on Saturday. The 33-year-old's serve is the least praised of his repertoire but it was his awesome delivery that blunted Djokovic's baseline game, taking his career ace haul past the 9,000 barrier with 12 more, several at vital moments. The match, the 37th in their rivalry which Federer now leads 20-17, proved to be a tale of chances taken and chances missed -- Federer converting his two break points with clinical efficiency, while Djokovic failed on all seven of his. I definitely won the big points tonight." Djokovic had two set points to level the match in the second set but both times Federer was rescued by his serve.