What is the core of component-based software development (the technical core of software engineering)

What is the breakthrough of the component-based software development method compared with the traditional software development method? First, the architecture of the software architecture represents a system of public *** high-level abstraction, it is the key to the success or failure of the system design

The core of its design is the ability to use the repeated system model

Traditional application system architecture from the centralized framework based on the mainframe to the framework of the client in the network to access the server over the network, can not be adapted to the current business enterprises are located in the business environment due to the fact that enterprises are overly dependent on a single vendor for their software and hardware products

This single vendor makes it difficult for enterprises to take advantage of the free market of computing vendors and leave important decisions about computing infrastructure to third parties, which is clearly not conducive to the enjoyment of information among partners***

It is not adaptable to remotely accessed, distributed, multi-tiered, heterogeneous systems

Encapsulated application systems are difficult to maintain with customization when some organizational need arises, thus making it difficult to meet changing requirements

Cannot achieve analysis, design core functionality reuse, or at best code reuse

Today's applications have evolved into distributed, multi-tiered, heterogeneous systems that can be accessed remotely by a wide variety of clients on the Intranet and the Internet. CBSD provides a new system architecture for developing such applications

It is a standard-defined, distributed, modular structure that allows applications to be developed in several independent parts and to be developed in an incremental manner

This architecture fulfills the following goals of CBSD: the ability to develop applications through Integration and customization of applications through internally developed, third-party provided, or commercially available building blocks

Encouragement of reuse of core functionality across applications, and efforts to reuse analysis and design

Systems should be flexible and easy to upgrade and maintain with updates to system modules

Encapsulation of best practices and ability to be customized to meet the needs of a wide variety of applications even as business conditions change

Containment of best practices and ability to be customized to meet the needs of a wide variety of applications even as business conditions change. change in business conditions, but also be able to be adopted, and can retain the existing resources

This shows that CDSD from the system of high-level abstraction to solve the reuse and heterogeneous interoperability, which is the distributed network system hopes to solve the problem

The second process of development of the traditional software development process in the reuse of elements, the development of methods are very different from the CBSD

Though object-oriented technology facilitates the use of object-oriented technology, the development of the system should be able to use the best practices of the system. p>While object-oriented technology promotes software reuse, it only realizes the reuse of classes and class inheritance

There is still a big gap between the whole system and the classes

In order to fill the gap, people have thought of many methods, such as system architecture, frameworks, design patterns and so on

Since the emergence of components, the reuse of software has only been fundamentally changed

CBSD achieves reuse at multiple levels of analysis, design, and classes

Figure 1 shows a hierarchical implementation of its reuse elements

At the analysis and abstraction level, the reuse elements are subsystems and classes, and at the design level, the reuse elements are system architecture, subsystem architecture, design patterns, frameworks, containers, building blocks, class libraries, templates, and abstract classes

In terms of software development methodology, CBSD guides software development from application development to application integration

Building an application system requires the reuse of a number of existing building blocks, which may have been developed at different times, by different people, and for a variety of different purposes

In this case, the process of application development becomes a review of the component interfaces, component contexts, and framework environments

In this case, the application development process becomes a review of the component interfaces, component contexts, and framework environments.

For example, in the J2EE platform, with the EJB framework for the development of applications, the main work is the application logic, according to sessionBean, entityBean design and development, and the use of JTS transaction services to realize the application system

The main difficulty is the transaction division, components of the deployment and development environment configuration

In summary, the traditional software development process is a serial waterfall, pipeline process; and CBSD is concurrent evolutionary, continuous upgrading and improvement of the process

Figure 2 shows their differences

Three, software methodology software methodology is from a variety of different perspectives, different ways of thinking to understand the nature of software

The traditional software methodology is from a variety of different perspectives, different ways of thinking to understand the nature of software

The traditional software methodology is from a variety of different perspectives, different ways of thinking to understand the nature of software

Traditional software methodology is machine-oriented, data-oriented, process-oriented, function-oriented, data flow-oriented, object-oriented and other innovative views to reflect the essence of the problem

The entire development of software has led to a growing realization that people should be in accordance with the laws of the objective world to solve the software methodology

Till the emergence of the object-oriented approach to software methodology to take a big step forward

The object-oriented approach to the emergence of the object-oriented approach to software methodology.

But the difficulties of high-level reuse and distributed heterogeneous interoperability have not yet been solved

CBSD has evolved to the present day, and only today does it provide an opportunity for solving this problem in software methodology

It separates the business of the application from its implementation, i.e., the separation of logic and data, and provides a standardized interface and framework to make the software development methodology into a combination of building blocks

Thus, the software methodology is interface-centered and behavior-oriented design

Figure 3 shows its development process

In summary, the software development methodology of CBSD should include the following aspects: a clear definition of the building blocks

The concept of building block-based requires building block description techniques and specifications, such as UML, JavaBean, EJB, Servlet specifications, etc.

Development of applications must be tailored to the components of the division of the organization, including the assignment of different roles

Tools to support the verification of the characteristics of the components and the generation of documentation, to ensure that the implementation of the component specifications and quality testing

In short, the traditional software methodology from the draft of the top-down process, the reuse of the no more assistance

CBSD's software methodology is much richer, it is plug-and-play, based on architecture, centered on interfaces, and combining components organically, it combines top-down and bottom-up approaches to development

Four, development organization The development organization of traditional software is usually made up of analysts, designers, programmers, and testers

For a small application system. A skilled developer, may take into account the above roles

But for CBSD, because component development and application integration is often carried out separately, so the entire development process is completed by the six roles, they are: component developers are also component suppliers, most of these are middleware components to provide (continued to the letter to a page on the contents of the web)

Application Component Integration The application developer is also a component supplier, and most of these are middleware component providers

Application Component Integration (ACI) is the process of combining existing components into larger component modules or containers for an application domain, as the basic unit of system deployment

Application Deployer (AD) is the process of placing the basic unit of system deployment into the selected platform environment or basic framework, to complete the requirements of the customization of the software

Development Platform Server Provider (DPSP) is the provider of the server, the operating system, and the database and other basic software

Application development tool providers to provide component public **** facilities services

System administrators to configure the hardware, network and operating system, supervision and maintenance of the application system

The six roles of the work of the highly specialized, it is difficult to take into account to become a multi-faceted

Currently, there has been the formation of components of the open market, and also a very red

This is also the present software Talent war encountered a confusion

Therefore, in the CBSD, how to organize the development team is particularly important, must be in accordance with the enterprise has the talent to organize

Particularly important: the development of the early stage of the standard framework must be selected, as well as the development of a unified guideline to ensure that throughout the development process, the roles of the various roles can communicate with each other at any time

Generally speaking, the quality of the personnel of the CBSD determines the quality of the components. The quality of CBSD personnel determines the reuse rate of components

V. Construction methodTraditional application software is constructed using a white-box approach, the implementation of the application system is all in the code, the application logic and data bonded together

And the construction of the CBSD is to use a combination of white-box and black-box approach

Component-based framework is to support the evolution of the use of two concepts: The first concept is that the artifacts have strong performance interfaces, so that both the artifact logic functions and the implementation of the artifact model are hidden

Thus, the artifacts can be replaced as long as the interfaces are the same

The second concept is implicit invocation, i.e., in the artifact-based framework, the artifacts' interfaces are never assigned an address directly, but only after the user of the artifacts is recognized

Therefore

The component user only needs to know the interface requirements and the return information from the reference provided for the component interface (which may be a component or a component agent

For the component user, the component agent is the component, there is no need to distinguish between them)

The information about the component's interfaces is not stored in the component, but in the component repository or registry

This ensures that component are flexible to be replaced and easily redeployed using implicit calls

Because the implementation of the artifact is transparent to the user, the artifact can also be adapted to a wide range of individual requirements

For this reason, artifacts provide both self-testing and normalization mechanisms

Self-testing ensures that information about artifact interfaces can be accessed without knowledge of the artifact's implementation

For example, the The self-testing mechanism provided by JavaBean is Reflection and BeanInfo, through which all the methods of the bean's artifact can be obtained directly, and through which many complex information about the artifact can be obtained directly

Normalization allows modifying the artifact without accessing it, such as the normalization provided by JavaBean is Propertysheet and customizer

Provide a simple set of parameters through the propertiesheet to modify the properties of the bean