January 10, 2005
Why use COM you should consider using COM to create a distributed application. Com windows2000 provides a robust development platform. This platform consists of several core technologies, providing basic components for creating multi-layer business applications. In general, the more supported by the basic platform, the less the code required and debugged. High-level overview of distributed services Any large multi-layer applications require services such as transaction support, integrated security, web servers, message processing mechanisms, and event notifications. The deadly weaknesses of history (from two-layer system to multi-layer system)
User interface business logic and data access code is mixed, making it difficult to reuse business logic and data access code between multi-client applications. Each customer application is implemented by business logic and data access code, running in their independent processes, so they cannot share proprietary resources, such as threads, memory, and more. Each client computer requires one or more dedicated drivers to apply sessions with a database server or a host. Enable customers to maintain expensive. Customers are very difficult to access data from multiple data sources. Applications can only be used for LANs, establishing a cross-regional distributed application is impossible. Applications are limited in a specific platform. When the client is disconnected, the two-layer system will stop working. System availability is limited. The separation display layer introduces the intermediate layer to reduce the coupling between the customer application and the business logic and data access code by introducing a group of business objects Business Object. The display layer defines a customer app that includes a user interface code is often referred to as a display layer Presentation tier. The platform of business objects supports business objects to concentrate your business logic and can apply multiple customers. These business objects can be configured using COM based on WindowNT and 2000-based networks. COM also provides customer application with intermediate layer objects to remotely communicate. One of the biggest selling points of COM allows middleware programmers to update their business object code without recompilation or re-distribute client applications. Another powerful feature of COM is that it allows customers to create and use objects between networks. In the background, COM uses the remote procedure to call the Remote Process Call, the RPC protocol spans the process and the host boundaries. One of the biggest power of multi-layer structure is that it is compromising the company's continuously evolving IT infrastructure complexity. Maximum limits for multi-layer applications based on CS mode (a development style) typically require that each user is running on a single platform, such as Windows. A web-based development policy can be used to greatly increase the number of users. Based on multi-layer application based on a web-based system, the customer application is running in the browser. The browser uses a simple hypertext HTTP to the server, and the display layer is built with hypertext tag language HTML. of. The use of HTTP and HTML is in that all mainstream platforms support them. In this way, your application has the potential of any user who can reach the Internet. The foundation of multi-layer strategy: Commerrosoft multi-layer strategy is based on a core technique called component object model COM. COM involves a large number of underlying details, for multi-layer applications, we will focus on the important COM details for creating intermediate-level transparent components. Multi-faced look of COM
