Every officer, agent, and employee holding a position upon an annual salary shall, before entering upon such person's duties, take and subscribe and file with the recorder, an oath or affirmation that such person has all the qualifications named in this charter for the office or employment such person is about to assume, that such person will support the constitutions of the United States and of this state and the charter and ordinances of the city and will faithfully discharge the duties of the office or employment.