Introduction The complexity of the software system is growing. The frequent flow of software people and the fierce competition in the software industry have forced software companies to improve software quality, accumulate and curing knowledge wealth, and shorten the development cycle of software products as much as possible. Therefore, "CBSD, CBSD, CBSD, and Component Based Sortware Developments" integrating software multiplexing, distributed object computing, and enterprise application development, and this technology is assembled in software architecture. With the reused software components as the assembly module, supporting the multiplexing of assembled software has greatly improved software production efficiency and software quality. For this study of the country, the research of this technology is continuously in-depth, and large software companies (such as Sun, Microsoft) and Software Organizations (OMG) have launched a software platform that supports middleware technology. In the face of high-profile technologies and a wide range of software platforms, many people feel very stunned and uns, this paper briefly introduces the development and characteristics of middleware technology, focusing on and comparing three main mainstream middleware technology platforms, making readers The middleware technology has a comprehensive understanding. The concept and development of middleware technology, the middleware is a class of software between application software and system software, is a class software independent of hardware or database manufacturers (in the middle of its products, achieving their interconnect). The connectors between the client and the server are the intermediate products that require secondary development. It should be said that middleware technology is an object-oriented technology that has been developed with the network. The previous computer system is mostly a stand-alone system, and multiple users are accessible through online terminals, and there is no network concept. After the network appears, the CLIENT / Server computing service mode is generated, and multiple clients can share database servers and print servers, and the like. With the further development of the network, many software need to operate in network products, hardware platforms, network protocols of different manufacturers, and the size of the application is also developed from the LAN. In this case, the limitations of the Client / Server mode are also exposed, so that the middleware came into being. The middleware is a general service between the operating system and the application software. Its main role is to block the differentiality of the network hardware platform and the isomer of the operating system and the network protocol, so that the application software can be operated relatively smooth. on the platform. At the same time, middleware has played a lot of role in load balancing, connection management, and scheduling, making the performance of enterprise-class applications greatly improved, meeting the needs of critical business. The currently supported server-side intermediate technology platform examines the current mainstream distribution computing technology platform, mainly OMG CORBA, Sun's J2EE and Microsoft DNA 2000. They are all platforms that support server-side middleware technology development, but they have their own characteristics, which will be set forth below. OMG CORBA CORBA Distribution Calculation Technology is a public object requesting agency system specification based on the distribution objects submitted by the OMG organization based on the distribution objects submitted by many open system platform vendors. CORBA distribution computing technology is the system specification technology supported by most distributed computing platform manufacturers, with a full range of models, advanced, independent system platforms and development languages, and has been widely supported. It has gradually become distributed. Standard. The COBRA standard is mainly divided into 3 levels: objects request agency, public object services and public facilities. The bottom layer is the object request proxy ORB, specifies the definition of distribution objects (interface) and language mapping, communication and interoperability between objects, is the "soft bus" in the distribution object system; there are many public services to the ORB. It is possible to provide a wide range of services such as concurrent services, name services, transaction (transactions) services, security services; the top-level public facilities define the component framework, providing services that can be used directly to business objects, specifying business objects The agreement rules needed to work effectively.
At present, CORBA-compatible distribution calculation products are endless, including ORB products of middleware manufacturers, such as BEAM3, IBM Component Broker, products with distributed object vendors, such as Ionaobix and Oocobacus, etc. The recent development of the CORBA specification, adding to Internet Characteristics, service quality control and CORBA component model (CORBA Component Model). Internet integration features include a firewall (FireWall) and Naming Service, which defines the URL naming format for IIOP transmission. Service quality control includes an asynchronous message service capable of quality control, a set of request schemes for real-time CORBA and fault tolerance CORBA for embedded systems. Corba CCM (CORBA Component Model) is based on the CORBA specification (after version 2.3) that supports PoA, it is developed based on the current specifications of the EJB. The CORBA component model is a server-side middleware model specification for the development and configuration of distributed applications, which mainly includes the following three items: a. Abstract component model to describe server-side components structure and components Interoperability; B. Component container structure to provide general components to operate and manage the environment, and support integration of system services such as security, transactions, persistent status; C. Component configuration and packaging specifications, CCM use packaging technology To manage the binary, multilingual version of the component, multilingual version of the multi-language version, and make the specific content of the component package and XML-based document content standards. In summary, CORBA is characterized by large, interoperability and openness. The disadvantage of CORBA is a large and complex, and the technology and standard updates are relatively slow, and the time of the COBRA specification is very short from 1.0 upgrades to 2.0, and the release of the release is relatively slow. It is not a lot in specific applications. SUN J2EE In order to promote Java-based server-side application development, Sun has launched Java2 technology and related J2EE specification by the end of 1999. The J2EE's goal is to provide platform-independent, portable, supported access and safe, completely Standards for the Intermediate Parts Based on Java Development Server. In J2EE, Sun gives a complete Java language-based development-oriented application specification, where J2EE supports RMI and IIOP, while the constructor of server-side distributed applications, including Java servlet, JSP (Java Server page), EJB and other forms to support different business needs, and the Java application has the characteristics of "Write Once, Run Anywhere", so that J2EE technology has developed rapidly in the field of publishing computing . J2EE simplifies the components expandable, which is the complexity of component server-side applications, although DNA 2000 is the same, but the biggest difference is that DNA 2000 is a product, J2EE is a specification, and different manufacturers can realize their own J2EE specification. Products, J2EE specification, is a numerous manufacturers to develop, it is not unique to Sun, and it supports cross-platform development, and many large distributed computing platform manufacturers have publicly supported J2EE compatibility technology. EJB is part of the Java-based server-side component specification J2EE, which is launched by Sun, has been widely developed since J2EE is launched, and has become standard technologies for application server. SUNEJB technology is based on the local components of Java Bean, developing application components for server-oriented distribution applications. It is based on Java language, providing a reuse of Java binary bytecies. EJB gives the system's server-side distribution component specification, including the interface specifications of components, component containers, and standard specification content such as component packaging, component configuration, and the like. The introduction of EJB technology makes it possible to use Java based component-based development server-side distributed applications. From the perspective of the multi-layer structure from the enterprise, EJB is the middleware technology of the business logic layer. Unlike JavaBeans, it provides the ability to transaction, since the three-layer structure is proposed, the intermediate layer, the business logic layer, is a handling transaction The core, separated from the data storage layer, replaced most of the storage layer. From the perspective of distributed calculations, the EJB is the basis for distributed technology like CORBA. Providing communication means between objects.
From the perspective, EJB and Servlets, EJB and Servlet, JSP become a new generation of technical standards, and the Bean in EJB can be divided into session beans and entity beans, former maintenance sessions, the latter handled transactions, now servlet is responsible for the client Communication, access EJB, and return the results to the client through the JSP generation page. The advantage of J2EE is that the mainstream of the server market is still a large machine and UNIX platform, which means that "WRITE, RUN Anywhere" can be configured to include any server, including Windows platform, with Java development components. Go in the environment. Microsoft DNA 2000 Microsoft DNA 2000 (Distributed Internet Applications) is Microsoft to extend the distribution calculation model, and the new distribution calculation architecture that is extended after the distribution calculation model, and the retrofit BACK OFFICE series server-side distribution computing product. specification. On the server side, DNA 2000 provides applications for ASP, COM, Cluster, etc. Currently, DNA2000 has huge advantages in technology structures. On the one hand, since Microsoft is an operating system platform manufacturer, DNA 2000 technology has been strongly supported by the underlying operating system platform; on the other hand, due to the extensive application of Microsoft operating system platform, the number of application development manufacturers supporting the system platform has many times, so In practical applications, DNA 2000 has been adopted and supported by many application developers. DNA 2000 integrates today's most advanced distribution calculation theory and ideas, such as transaction, scalability, asynchronous message queues, clusters, and more. DNA enables development of server components that can be based on Microsoft platforms, such as database transaction services, asynchronous communication services, and security services, are provided by the underlying distribution object system. DCOM / COM / COM camp headed by Microsoft, from DDE, OLE to ACTIVEX, etc., provides the basis of middleware development, such as VC, VB, Delphi, etc. Support DCOM, including OLE DB, new data inventory, With the release of Windows2000, Microsoft's DCOM / COM / COM technology, on the basis of the DNA2000 distribution computing structure, a new distributed component application model is displayed. First, the components of the DCOM / COM / COM still use a common COM (Component Object Model) model. COM initially serves as a Microsoft desktop system, mainly for local OLE applications, but with the release of Microsoft Server Operating System NT and DCOM, COM has extended component technology to distribute applications. DCOM / COM / COM will extend it to a business logic middleware for a server-side distribution application. With COM related service facilities, such as load balancing, memory database, object pool, component management and configuration, etc., DCOM / COM / COM combines COM, DCOM, MTS's functionality, forming a concept, strong Component application architecture. Moreover, the DNA2000 is a single manufacturer's distributed object component model, and developers use the series of development tools provided by the same manufacturer, which is more attractive than a combination of many developments. However, it is insufficient to depends on Microsoft's operating system platform, and thus does not work on other development system platforms (such as UNIX, Linux). Correlation Comparison Analysis Currently, similarly, similarly, comparable distributed components, such as Corba CCM (Corba Component Model), Sun's EJB (Enterprise JavaBean) Technology and DNA 2000 COM / DCOM / COM technology. For the above three distribution computing platforms, this paper uses the industry's commonly used practices to analyze the following three aspects: Integration: Integration is mainly reflected in the basic platform support for application interoperability. It requires distribution on different machine platforms and operating systems, all kinds of business applications generated by different languages or development tools must be integrated to form a unified enterprise computing framework.
