基于软件体系结构的反射式中间件研究

Internet为分布应用提供了一种开放、动态的运行环境,这要求分布应用的主要基础设施中间件能够支持运行时查看并调整平台内部状态和行为,由此产生了反射式中间件.目前的反射式中间件研究与实践存在3个不足:注重系统局部或单个实体的反射而缺乏全局视图;注重中间件平台内部功能的反射,而对上层应用的反射不够;集中于CORBA平台,而对J2EE平台的反射性研究较少.介绍了一个反射式的J2EE应用服务器PKUAS.基于构件化的平台内部体系结构,PKUAS引入软件体系结构作为全局视图以实现反射体系对系统整体的表示和控制,作为J2EE应用服务器,PKUAS可反射底层平台以及上层EJB构件.同时,以PKUAS实时监控工具为例,探讨了如何利用基于软件体系结构的反射体系管理整个系统,并给出了PKUAS与其他几种反射式中间件的比较.该工作有效地解决了现阶段反射式中间件研究的不足,提高了反射式中间件的实用性.

Research on Architecture-Based Reflective Middleware

As Internet provides an open and dynamic runtime environment for distributed applications, one of the most important challenges to the next generation of middleware is how to allow the observation and manipulation of the runtime states and behaviors internal of middleware platform. Reflective middleware is able to open up the platform implementation to meet such requirements. There are three limitations in current research and experiments on reflective middleware: they focus on parts or individual entity of a system, lacking a global view; they only address the reflection of the underlying platform, ignoring the reflection of the application; they mostly experiment on CORBA with less work on J2EE. The design and implementation of a reflective component operating platform, called PKUAS, is presented. Based on its componentized structure, PKUAS introduces software architecture as the global view of the whole reflective system. As a J2EE-compliant application server, PKUAS can reflect both the underlying platform and EJB components. Moreover, this paper demonstrates the usage of reflection with the PKUAS management tool and evaluates PKUAS through comparison with other reflective middlewares. The work presented in this paper addresses the aforementioned limitations and improves the applicability of reflective middleware.