Abstract
A Geant4-based simulation framework for rare event searching experiments with germanium detectors named SAGE is presented with details. It is designed for simulating, assessing background distribution, and investigating the response of the germanium detectors. The SAGE framework incorporates its experiment-specific geometries and custom attributes, including the event generators, physics lists and output format, to satisfy various simulation objectives. Its docker image has been prepared for virtualizing and distributing the SAGE framework. Deployment of a Geant4-based simulation will be convenient under this docker image. The implemented geometries include p-type point contact and broad energy germanium detectors with environmental surroundings, and these hierarchical geometries can be easily extended. Users select these custom attributes via the JSON configuration files. The aforementioned attributes satisfy the simulation demands, and make SAGE a generic and powerful simulation framework for the CDEX experiment.