摘要
程序设计方法学一直是软件工程领域的核心问题。传统的编程方法，如OOP(面向对象编程方法)，已经很难满足应用系统复杂性和分布性的需要，组件化编程方法和组件模型应运而生。Microsft提出了COM(组件对象模型)以及一系列基于COM的技术，如DCOM、ActiveX、COM+，用于构建组件编程框架。基于COM可以构建可复用性好、易维护、稳健的系统。
本文对COM技术底层实现机制进行了研究。文章从COM技术的支持环境出发，分析了COM底层的运行机制，阐述了COM组件的若干特征在Windows平台上的实现方式，并对COM进程内组件的运行环境进行模拟，为COM向非Windows平台的移植做了部分前期准备工作。模拟的主要内容包括组件对象的内存管理机制、组件的集成机制、COM库中部分核心API函数。
本文对COM的通信机制进行了研究。文章分析了COM列集机制和可连接点机制对多点通信的支持，提出了一个新的通信模型—基于COM的多点通信模型，讨论了模型的负载平衡、容错性、安全性，初步实现了模型中主要对象，并规范了对象接口间的调用关系。提出了静态和动态相结合的集中式负载平衡解决方案。该方案应用可连结对象的回调机制，实现服务器负载信息的自动收集；通过客户动态配置DCOM服务器位置的方式，方便的实现任务调度；通过引入最优备用服务器和最优服务器的概念来作为任务再分配时的调度服务器的依据，实现较好的容错性能。
文章最后对论文的研究工作进行了总结，并对基于COM的通信模型的进一步研究指出了方向。
The methodology of programming is one of the focuses in the field of software engineering. The traditional programming methods such as OOP(object-oriented programming) could not satisfy complex and distributed applications, so component software and component models come up. COM(component object model) and other technologies derived from COM, such as DOOM, ActiveX, COM+, are developed by Microsoft to establish component-based programming architecture. Reusable, maintainable and robust applications could be constructed based on COM.
This paper researches the mechanism of COM, in which the supporting environment of COM technology is analyzed, the inner running mechanism is studied, the characteristics of COM component and their implementations on Windows platform are set forth, and the running environment is simulated, which is prepared for COM transplantation from Windows platform to others. Subjects of COM in-process server have been simulated: 1 . the mechanism of memory management; 2. the integration of component; 3. some of the kernel API functions in COM library.
The paper researches the communication mechanism of COM, in which the technologies of marshaling and connection point support the COM group communication is analyzed, a new communication model?group communication model based on COM is put forward, load -balance, fault-tolerance and security of the model are studied, the main objects in the model are implemented and the interactions among their interfaces are normalized. The author presents a kind of new centralized load-balance algorithm based on static and dynamic task scheduling strategies. This algorithm can work better in realizing gathering load information automatically by applying call-back mechanism of connection object, assigning tasks conveniently by configuring DCOM server, and tolerating fault during several emergencies by introducing the concept of optimum-server and optimum-spare-server into task reallocation.
A summary of the works is given and the future work of the communication model based on COM is pointed out in the end of this paper.
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