Spring Web Flow (SWF) is a controller framework for building Java-based web application modules. The framework is specifically targeted at managing multi-step page flows; good examples are things like booking flights, applying for loans, paying your taxes; basically web conversations with well-defined lifecycles, and typically those transactional in nature. Essentially we allow developers to develop these encapsulated, self-contained controller modules called "flow definitions", and the system then allows users to launch executions of them at runtime. These "flow executions" are stateful constructs based internally on a finite state machine which runs on the Java VM.