Research And Implementation Of Scalable Distributed Applications Based On COM+

With arrival of information age, computer gets more and more extensive application in all trades and professions. Hospitals are equally faced with enormous challenge in information age too. A scientific and logical hospital information system can improve management of hospital and support medical, teaching. Hospital Information System belongs to one of the most complex enterprise information systems hitherto. Construction cycle of traditional HIS based on client/server is long and function is not perfect enough, they have generally the phenomenon and questions that system responds slowly, centralized control is difficult and dependability is poor. So it needs one kind of scientific method to analyze and design Hospital Information System. In Hospital Charging System that this paper will talk about is a subsystem of Shenzhen 999 hospital information system (999HIS). This system adopts object-oriented modeling technology and method which can more deeply catch the requirement of users and setup good base for successful development of this system and software maintenance during later stage. It is Windows DNA system structure based on three layer structure and COM+ technique criterion adopted in development process that make the development cycle abbreviate and the system performance, scalability and security improve greatly. While structuring a distributed application system, we always face some problems such as consistent maintenance for data, parallel running, scalability, security, transaction processing, and arrangement of application program. In the field of computing distributed, many kinds of different application modes appeared to solve the complicated commercial demands. But how do we organize computers on the network, make them coordinate and work, stand up an enormous potentiality distributed and parallel environment, enable the different procedures on different machines to work mutually, and develop the large-scale, complicated and scalable distributed enterprise's application program has already become the focus of the present development. As to the main problem that the present distributed computation faces, this thesis adopts a more popular application structure –three tier distributed application system based on COM+. This system can provide services for many clients parallel, but have a scalable system structure. Comparing to traditional distributed computation structure, this structure has embodied superiority. Adopting the solution with Microsoft Windows DNA framework, this thesis expounds that distributed application based on COM+ has feasibility and flexibility, thus solve all sorts of technologic difficulties that existing HIS system faced with. This thesis mainly discusses COM+ operation mechanism, including process, thread, object, transaction, operation principle and technological characteristic of communication protocol. Just the advantages of COM+ enable developers to concentrate on programming the commercial logic as to their application demand, just as the component is used by individual user. Using SOAP as tool, it proposes a model that can step the network, step system, and step object model so as to access to the other application component. It also discusses how we design component interface according to COM+ standard. At the end of the article, combining a concrete application –In Hospital Charging System which is a subsystem of Shenzhen 999 hospital information system (999HIS), it discusses how we use scalability to solve the practical problem effectively and conveniently. Using COM+ multi-layer technology divides this system into user layer, business logic layer, and data visited layer. User interface layer connects with all of user, which includes user interface and all display logic. The business logic layer is the key point of an application system. It runs with the request of all users, and returns the processing result to the display layer. Data visited layer offers database support, and adopts some simple storing procedures to maintain data. In order to make the object roam in different processes, threads and machines, the object must be disconnected with the server. That is to say, the object is stateless. So ADO recordset must be realized. The attributes of the object, which is stored with ADO Recordset but not in object itself, should be...