This article is the second article of architecture web services, starting from the technical definition of web services to explore what is web services. First, the author analyzes the basic role of Web services as a basic role of software components in the Internet environment. From this basic role, detail the packaging specification of this component object Web Service "stack", and do the application of Web services Classification, finally investigated the current development status of Web services with Garnter Group.
In the previous article of this series, I will analyze the web services, from the perspective of commercial interest demand. This article will combine the development needs of technology drivers, detail the technical perspective, what is the web service, and the application classification of Web services. In terms of technical perspectives, regardless of which point of view, Web services are Object / Component technology extension in the Internet.
The resources cited herein mainly include two categories, one is the technical resource website of web services, including the technical information of a large number of web services, and the other is the "Stack" technical specification of the web service, they are a whole technical system. Including UDDI, SOAP, WSDL, XML, etc. The links of these resources are given in this article, and interested readers can find the desired content through these resource links.
Web object
From the perspective of external users, the web service is an object / component deployed on the web, which has the following features:
For intact encapsulation, since it is a good encapsulation of objects deployed on the web, it naturally has good encapsulation of objects. For users, he can only see the function list provided by the object. Loose coupling, this feature is also from object / component technology. When a web service is changed, the caller does not feel this. For the caller, as long as the call interface of the web service is unchanged, Any change in Web services is transparent to them, even when the Web service is migrated from J2EE to .NET or the opposite migration process, users can know nothing. For loose coupling, especially Web services in the Internet environment, there is a need for a message exchange protocol that is suitable for the Internet environment. And XML / SOAP is currently the most suitable message exchange protocol. Using the specifications of the usage, this feature comes from the object, but compared to the general object, it is more standardized and easy to understand. First, as a web service, the functions provided by the object interface should be described (such as WSDL) using standard description languages; secondly, the service interface described by the standard description language should be discovered, so this description document needs to be stored. In the private or public registration library. At the same time, the use of standard description language description will not only the service interface, it will be extended to the aggregation of the web service, transactions across the web service, workflow, etc., and these require service quality (QoS) guarantees. Second, we know that the security mechanism is the importance of loosely coupled object environments, so we need to use specifications such as authorized certification, data integrity (such as signature mechanism), non-denial of message source authentication, and transaction, etc. Transmission and exchange. Finally, all levels of processing should be manageable, so you need to use the same mechanism to manage the administration. With standard protocol specifications, all public affairs are fully described, transferred, and exchanged using open standard protocols. These standard protocols have a completely free specification for any party. In general, most specification will eventually have W3C or OASIS as the final version of the publisher and maintenance party. Highly integrates. Since the Web service takes a simple, easy-to-understand standard web protocol as a component interface description and collaborative description specification, completely blocking the differences in different software platforms, whether it is CORBA, DCOM or EJB can be interoperable through this standard protocol To achieve the highest integrated integration under the current environment. Web service "stack"
In the previous section, we have learned that in order to complete object access in a loosely coupled environment, as well as transactions, workflow, safety mechanisms, such as transactions, workflow, safety mechanisms, etc. above basic objects. Realizing a complete web service system requires a series of protocol specifications to support.
Figure 1. Web Service "stack"
Among them, the green part is the standard: IP, HTTP, SMTP, etc., which have been previously defined and widely used. The blue part is a standard protocol for Web services currently developed, including service call protocol SOAP, service description protocol WSDL, and service discovery / integrated protocol UDDI, and service workflow description language WSFL. The orange section describes an agreement on routing, reliability, and transaction. The yellow part is a common mechanism for each protocol layer, which is generally completed by an external orthogonal mechanism.
From the above technical level, we look at it, the first goal pursued by web services is simple. Maybe everyone will feel very strange, there are so many agreements, how can he say that he is simple.
First, these agreements themselves are simple, whether it is a network protocol of traditional TCP / IP systems such as HTTP, FTP, or SOAP, WSDL, UDDI, WSFL, etc. Based on XML protocols, one of their design principles is to Strive for simplicity. I believe that if you have an in-depth understanding of XML, SOAP, you will definitely understand this. Second, a web service that can be used should be used in accordance with a number of features that need to be used without any feature. For example, in the current situation, a simple application may only use WSDL / SOAP to schedule a standardized web service.
Finally, all mechanisms are completely based on existing technologies and have not created a complete new system. Whether it is IPv4, HTTP, FTP these existing network protocols, or SOAP, WSDL and other XML-defined protocols are followed by a principle: inheriting the originally accepted technology, so that Web services can be widely accept.
WEB service category
Comprehensive Web application and the characteristics of Web services, we believe that the field of Web services can be divided into four categories:
Business-Oriented Web Service: This type of service is for enterprise application services, including ERP systems, internal ERP systems, and SCM / CRMs between enterprises. When these systems appear in the web service, the application integration within the enterprise is not easily, and the system docking of many partners in the enterprise will no longer be completed. Currently, existing solutions and product providers include Bowstreet, Epicentric, and more. Consumer-Oriented Web Service: This type of service is for the original B2C's renovation, and adds to these Browser-Oriented web applications (note that it is increasing) the application interface of the web service, making third-party desktop tools or them. The value-added desktop tools provided can provide a desktop service across multiple B2C services using a better user interface. This will make the user more convenient to use Internet and get more convenient services. For example, we can integrate (call) the stock price on the Internet in a personal wealth management desktop system, the ticket is scheduled for Web services, so that the degree of automation of personal financial applications is higher. Device-Oriented Web Service: The usage terminal of such services is generally handheld devices and daily appliances. For the former, the previous network service can support each other than the PC without the premise of the system architecture that does not have to modify the network service. Terminal, such as Palm, PocketPC, mobile phones, etc. In this way, those weather forecasts, email services, active information services, etc. will be more effective and convenient. The latter may be a market start-up period, which has a web service as a foundation framework, intelligent daily appliances will truly obtain standard support, there is a widely used possible possible. System-Oriented Web Service: Some traditional system services, such as user rights authentication, system monitoring, etc. If migrated to global Internet, or on intranet, its scope will range from a single system or local network Expand the entire enterprise network or the entire Internet. Thus, different applications based on the same system service will be deployed throughout the Internet environment, such as all online services of multinational companies can use the same user rights authentication web service.
Web service: Today's technology brightest point
Figure 2. Current development of Web services
This picture is the abstract model after the Gartner Group has studied the development path of all IT mainstream fashion technology. The Y-axis indicates the degree of focus on technology, while the X-axis represents the application of the technology. Each technique will be advanced along the curve in the figure from the entire process of maturity, and typically, it will be divided into five phases: technology shows that one technology is inventive or defined, starting to enter the public The field of view; the expected expectation of the expansion: Due to the erasable breakthrough of the technology, people have no better imagination and expectations for this technology, this stage is similar to the "network foam"; hoping after the wake off: Since each technology is not universal, truly use still needs pragmatic application research, so people find that this technology does not seem to be useful, this stage is similar to the "network bubble"; suddenly open and cheerful Application Development: After a stage of development and research, the technology finally embarked on the track of benign development, more and more people accepted and used the technology; a large number of industrial production period: this technology became industry Mainstream, a large number of applications in a specific environment.
