This paper describes an FSM (Finite State Machine) architectural framework called StateJ. In an FSM architectural framework, a business service is realized by a finite state machine and implemented as a component called service managed by the state management service. Distributed services communicate with each other through the request management service and event notification service. StateJ has been exploited to develop several service-based applications, in particular, telecom service provisioning systems. This paper describes the StateJ framework and the authors' experience of using it.