Classification and function of middleware

To clarify this problem, we use an example of life as a metaphor. The distributed system as the traffic system in downtown, the network as Urban road, through the transport (car) to achieve communication, every minute will have tens of thousands of cars on the horse road, if there is no corresponding traffic facilities and management planning, Beijing will be mess, the occurrence of various traffic accidents. 1. Communication processing (messaging) middleware

First of all, to repair the road, install traffic lights, set up traffic management agencies, the establishment of rules, that is, we want to build a network and develop communication protocols, can communicate between different platforms, to achieve reliable, efficient, real-time cross-platform data transmission in distributed systems (such as Tonglink, BEA Elink, IBM's MQSeries, etc.), called message middleware. This is the only indispensable in the middleware, is the largest demand for middleware products, currently in the Windows 2000 operating system has included some of its features.

2. Transaction processing (transactional) middleware

In a distributed transaction processing system to handle a large number of transactions, often in the system to do the same time tens of thousands of transactions. For example, in Beijing to set up a variety of vehicles to carry out the daily delivery, at the same time to monitor the operation of the car, when there is a failure, to have the elimination of measures, when the congestion should be dispatched. In online transaction processing systems (OLTP), each transaction is often ordered to be coordinated by multiple servers, and in the event of a failure in the middle, not only does the recovery work, but it also automatically switches the system to a system that never stops and achieves high reliability. At the same time, in order to achieve this goal, the system has the function of monitoring and dispatching the whole system, so that a large number of transactions can run concurrently in real time in multiple application servers and load balanced scheduling, so as to realize the same functions as the expensive reliability machine and large computer system. Bea's tuxedo is famous for this, and it has become the highest growth producer. A transaction processing platform, according to the parameter model of X/open, should be composed of transaction processing middleware, communication processing middleware and data access management middleware. The Tonglink and Tongeasy of Dongfang Tong Technology Corporation have realized this reference model stipulation.

3. Data Access Management middleware

In distributed systems, important data are stored in the data server, they can be relational, compound document type, with a variety of storage format of multimedia, or is encrypted or compressed storage, the middleware will be on the network virtual cache, format conversion, decompression and other convenience.

4. Web Server middleware

Browser graphical user interface has become a recognized specification, but its conversational ability is poor, can not write data, by the HTTP protocol restrictions, etc., it is necessary to modify and expand, the formation of Web server middleware, such as Silverstream Company's products.

5. Security Middleware

Some of the biggest barriers to access to the Internet in military, government and business sectors are security secrecy and the inability to use foreign-provided security measures (such as firewalls, encryption, certification, etc.) and the need for domestically produced products. Unsafe factors are caused by the operating system, but must be solved with the middleware to adapt to the requirements of flexible and changeable.

6. Middleware for cross-platform and architecture

At present, the development of large-scale application software is usually based on architecture and component technology, in the distribution system, but also need to integrate the various nodes on different system platform components or new and old version of the component, resulting in the framework middleware, the most powerful is CORBA, can cross any platform, but too large , JavaBeans is more flexible and simple, it is suitable for browser, but inefficient operation; the DCOM model is primarily suitable for Windows platforms and is widely used. In fact, the domestic new system is mainly UNIX (including Linux) and Windows, so it is much more practical to build corresponding middleware for these two platforms.

7. Dedicated Platform Middleware

Design reference patterns for specific application areas, set up the appropriate architecture, configure the appropriate component libraries and middleware, and develop and run key tasks in specific areas (e-commerce, websites, etc.) for application servers.

8. Network Middleware

It includes network management, access, Web testing, virtual community, virtual buffer, and so on, and is currently the hottest research and development projects.