Large-scale Wi-Fi networks have encountered several critical issues of access point (AP) management such as manual configuration, channel interference, and unbalanced loads, which should be carefully addressed to ensure efficient system performance. Since most of the commercial Wi-Fi products are proprietary and hardware-dependent, some recent studies have aimed at introducing open and programmable solutions. Unfortunately, the studies demand additional protocols and software agents but cannot provide complete solutions. To this end, this experience paper presents the design, prototype implementation, and evaluation of SAMF, which is an open, programmable, and generic framework for access point management in large scale Wi-Fi networks. By adopting the concept of SDN technology and OpenFlow protocol, SAMF can readily be deployed on low-cost commodity access point hardware and a cloud-based controller, while enabling new network services to be integrated rapidly. Furthermore, experimental results confirm that the framework can significantly reduce operational costs since it accelerates the AP configuration process by approximately 15 times. Besides, SAMF can increase system throughput up to 26.5% and improve the balanced degree of the system by about 40%.