Technology trends of application servers: Technical Director of Beijing Orient-technology companies Li Chunqing
Application Server is also known as "Application Server Software Platform, referred to as ASSP) is the most important type of intermediate software. The evolution of the middleware software market has created many types of middleware, making it clearly understanding of middleware solutions more complicated. I. Application Server and Application Server Software System Overall Structure In 1998, the National Giga Information Group's report "Understanding Middleware - Give IT Administrators' Policies and Recommendations", draw a very classic middleware position Two-dimensional maps are still applicable.
In the above figure, the vertical axis represents the distance from the low-layer communication protocol. The higher the position on the graph, it means that the product is getting closer from the application area, and more features needed in the application. In the above figure, the horizontal axis represents the type of abstraction, starting from the data on the left, by moving the abstract movement to the right, terminating abstraction based on objects and components. Some types of middleware such as transactional monitoring (TP Monitors, so-called "transaction middleware"), bridged multiple abstractions (such as data and processing), longitudinal direction to the high layer from the low layer. Other maintenance in the high layer, depending on the middle part of the low-level, such as using CORBA or J2EE technology, or DNA technology or application server for TP Monitor technology. The application server is not the location reset of the old product. First, it is not simply packaged in ORB, MOM, transaction management, data access middleware, and other middleware products and technology, because the current application server software is based on object or component technology, various middleware functions It must be provided in a object or component; in addition, it is necessary to add additional important, increased value functions - such as objects or components deployment, runtime, and management functions. According to the division of GIGA in 1998, there are four types of application server software according to the application type of application server software: for web high-end e-commerce applications, for high-end enterprise applications, for low to medium-size web applications, and Multilingual department-level applications. Today, applicable server software applied to enterprise-class e-commerce applications is generally attributed to the same category. There is still a software implementation that supports e-commerce or corporate sector applications that are low to medium business scale. In recent years, in addition to Microsoft's exclusive offer, the mainstream application server products are based on JAVA language, and comply with J1E / EJB specification based on DNA / DCOM technology. Based on J2EE / EJB technology, providing Web or independent program access, supporting the development, deployment, operation and management functions of enterprise Java Components (EJB), providing access to the background database system and enterprise information system, providing standard message transfer mechanism The application server software such as function has become the commonality of the current application server software. The overall structure of the software system based on the J2EE application server is shown below.
Overall, the entire software system based on ASSP is constructed from four large levels. The bottom is the Java Virtual Machine (JVM) layer, which is generally provided free of charge by computer system manufacturers; the above is ASSP, provided by ASSP developers. This layer is the infrastructure layer of the entire application system development, deployment, operation, and management is the content of this project to be developed. The upper-level e-commerce / enterprise application framework is based on ASSP development, "standard" building blocks for specific types of e-commerce / enterprise applications, this layer of products are provided by ASSP vendors or third-party software vendors. Similar products have an "e-commerce server", etc. The top layer is an e-commerce / enterprise application developed by application software developers / developers. In the longitudinal direction, the product and technology of the bottom layer are most standardized, the higher the level, the less standard, the more it needs to be customized. From the perspective of value, the closer to the final application solution is the most up. If the supplier of the underlying software can provide more content to the top layer, the more value added. Second, the overall trend of ASSP technology has integrated technical and market analysis institutions and our research, and the overall trend of ASSP technology can be summarized as the following five large directions. Overall, ASSP part has not changed, and the basic framework is not changed. The core content of ASSP is more standardized, and the ASSP contains more features, and the ASSP horizontal is more contact with other systems. The ASSP itself also extends upwards, accommodating the content of some application frameworks into itself. The above movement has a general meaning. Trend First, technology is increasing "standard", follow the "standard" to become 2000 years ago, with the popularity of the core of the serve party, such as JSP, Servlet, and market-to-enterprise Java component (EJB) The expectation, a large number of newborn companies flock to the market that builds server-side products to achieve these APIs. At this time, the manufacturer's concern is still constructing and selling its specific API products. By the end of 1999 and 2000, there were approximately more than 30 EJB server manufacturers, only a few companies achieve complete EJB1.0. The focus of the entire industry is an EJB application server, and each manufacturer is working hard to become a mainstream EJB server vendor. J2EE 1.0 The final specification requires "conforming to J2EE" specification and must provide a complete J2EE API product suite. From the J2EE Compliant Test of the 2000 Application Server Vendor, "J2EE" has become an inevitable choice for manufacturers to fight for competitive advantage. The entire J2EE system includes four parts: J2EE blueprint, J2EE specification, J2EE reference implementation and compatibility test kit. The norms include more than ten parts, involving many related technologies such as Java component technology, enterprise Java components technology. In the past few years, the relevant technical specifications have been constantly increasing, expanding and improving. At present, the latest version of J2EE and EJB is 1.4 and 2.0, EJB 2.1 has not been officially launched. As a modern application architecture that supports enterprise-level component applications, some of EJB2.0 are very important in Local Interface, CMP, EJB-QL, MDB, etc. Trend II, extended service and function are important features of ASSP J2EE / EJB has become the criteria for most application server vendors. The factors that have been distinguished from different application servers have disappeared. A fierce competition is increasingly manifested at a high level, no longer a low-tech level. Basically, the application server consists of the following core service / features and extension services / features.
In terms of core services / features, application server vendors have been transferred to J2EE "standard." Because the application server is becoming more and more standard in the core layer, the entire concept of the application server is as the standard part of the enterprise information system like the operating system. J2EE is playing an important role in the standardization process. Many of the predictions about ASSP believe that as J2EE has become a public standard for application servers, ASSP is getting less and less cheap, and the difference is getting smaller and smaller. The views of each ASSP vendor is that the standard makes it easier to program, but the performance, scalability, and make the product more quickly to the market, to distinguish each ASSP, thus resisting or delaying the process of "productization". This is also a cause of ASSP vendors to promote application development frameworks, new technology applications (see "Trend Three" and "Trend 4"). Therefore, the expansion service and functionality will become one of the key contents of the manufacturer's development of ASSP. ASSP's extension services and functions can be classified into the following middleware feature list (from Aberdeengroup "Intermediate Parts" report).
ASSP provides a basic framework that supports enterprise application development, deployment, and management. In the process of realizing general enterprise applications or specific types of applications, people have gradually summed up some common, verified analysis, design and implementation methods, and even partial implementation. Independent software vendors or ASSP vendors can further abstract these public designs and parts of a similar problem, providing a generalization solution - application development framework to simplify application system development. Based on the framework development of object technology, the core function is generally implemented as an abstract class interacting in a particular way. These abstract classes are replaced with specific subclasses when exporting a specific application. Other specific classes are selected from a component library provided by a frame developer. Customization is completed by adding some new application specific classes. Some application development frameworks are generally for specific applications or business types, and some are for some type of application or business, usually regard them as a platform software for some application or business application. Trend III, integrated new key technologies in recent years, in the field of distributed calculations, may have the influence of technology will eventually exceed Web Service. Although we have web information publishing and browsing technologies, J2EE / EJB, CORBA, and DCOM, etc., which is based on different application architectures, based on different application architecture, based on different application architectures, information on different operating systems. Inter-system inter-communication and information sharing are still facing challenges. In B2B e-commerce applications, companies need to achieve rapid, convenient and low-cost application integration with partners, suppliers, distribution and agents, banks. Solutions of existing EAI or other middleware are cumbersome, expensive, and not convenient to implement dynamic applications. Web Service technology can effectively solve this problem. Depending on IBM definition, Web Service is an interface that describes a set of operations that can be accessed by standardized XML messages on the network. Web service completes a specific task or a specific set of tasks. Web Service uses a standard, formal XML representation, the web service description, provides all details that need to be interactive with the service, including the format of the message (detail described here), the transfer protocol, and location. The interface nature hides the details of the service implementation, and the interface can be used independently of the hardware or software of the interface, and writes the programming language of the interface. This allows and encourages the loose clusters, components and cross-technical implementations based on Web Service-based applications. Web Service can be used independently or with other Web services to perform a complex collection or a business transaction. Therefore, major ASSP vendors, the entire software industry is optimistic about Web Service, which depends on the best way to solve the problem of loose integration of e-commerce, government affairs and other applications. According to IDC, "Western Europe ASSP Market Prediction and Analysis 2002-2006" (IDC # AD25J), IDC believes that, as the development of 2001, Web Service is increasingly considered to provide interoperability of technology. Important means, primary manufacturers have added basic Web Service capabilities in their products. By 2002 Web Service Standards (SOAP and WSDL) support is probably the feature of the product. IDC is confident that it is impossible to sell a product that does not provide basic support for WS. Before the EJB 2.1 specification is officially launched, some J2EE / EJB-based ASSSP products already have basic support for Web Service, such as by simply built-in some transfer handlers and a SOAP engine, you can encapsulate servlets and EJBs into Web service. In the EJB 2.1 specification, it is clearly defined for EJB to define components interfaces that support the Web Service, which makes the EJB support for web services programming and packaging processing standardization. New key technologies for ASSP are not limited to Web Service.
