Abstract: In order to achieve the architecture scalability and module portability， this paper introduces OSGi （open service gate way initiative） mechanism into application server， and discusses the refactoring approach. The existing problems are investigated， and three principles are proposed for the refactoring， including enabling information hiding to decompose the modules， enabling least intrusion to ease the maintenance burden， and enabling variability separation to enhance the extensibility. The practices and experiments have proved the efficiency. The principles and approaches can be applied to other application servers， and the similar software refactoring.

Key words: application server, open service gate way initiative （OSGi）, refactoring, information hiding, least intrusion, variability separation

摘要： 为了满足应用服务器的可伸缩、动态性及模块可移植，针对应用服务器目前普遍存在的问题，以自主研发的应用服务器PKUAS为例，面向OSGi体系结构进行了重构。深入探讨了问题存在的原因，提出了一组重构原则和方法，包括：遵循信息隐藏原则划分模块；遵循最少侵入原则以减轻维护负担；遵循变化性分离原则增强可扩展性。实践证明其效果良好。所提出的原则和方法适用于其他应用服务器，对采用OSGi技术进行重构的其他软件也有良好的借鉴价值。

关键词: 应用服务器, 开放服务网关协议, 重构, 信息隐藏, 最少侵入, 变化性分离