Prerequisite knowledge for WCF distributed development (4): Web Service

Continue today in our WCF Distributed Development Prerequisites Section 4th: Web Service. In the first 3 sections we introduced the MSMQ Message Queuing \.net remoting\enterprise Services three related technologies. and give detailed annotated code implementation examples. First, introduce the organization structure of the article in this section, first or 1. Basic concepts of Web Service 2. Advantages and Disadvantages 3. Use Web Service 4. Security issues 5. The implementation of the Code section is summarized. Beginners as a primer, master on the review, also welcomed the comments.

Now we start today's study, Web service information on the Internet a lot, but also very messy, confusing the basic concept.

The basic concept of 1.WEB service

What is Web Services? Web Services is a software system designed to support the support of machines and machines through network interoperability (definition of the consortium). is a set of applications that can be invoked over a network Api.web Services is an application component that communicates using an open protocol, Independent (self-contained) and self-describing, features that can be found by using UDDI and can be used by other applications.

The WEB services platform mainly involves XML \soap\wsdl\uddi four main elements. Here's a brief introduction.

(1) Xml:xml is the abbreviation for Extensible Markup Language, XML is an HTML-like markup language, XML is used to describe data, XML tags are not predefined in XML, you have to define your own markup XML uses a document type definition (DTD) or schema (schema) to describe the data, and XML uses a DTD or schema that is the self-describing language.

(2) Soap:soap (Simple Object access Protocol) an XML-based protocol is a simple protocol for exchanging information in a decentralized or distributed environment. It consists of four parts: Soap Encapsulation (envelop), which encapsulates a description of what the content in the message is, who sent it, who should accept and handle it, and how to deal with their framework; A SOAP encoding rule (encoding rules) that represents an instance of the data type that the application needs to use; A SOAP RPC representation (RPC representation) that represents a contract for remote procedure invocation and response; SOAP binding (binding), which uses the underlying protocol to exchange information.

(3) Wsdl:web Services describes language, which has five main components. Types: Defines the data type used in the WSDL definition, that is, the XML Schema Types; Message: Defines the input and output parameters of a set of messages; PortType: Defines the operation of a Web service; Binding: Describes the protocol, data format, security, and other attributes of a specific service interface.　　Services: Develop a URL for a specific service and a provided calling interface that contains a set of port elements. This enables Web services to be self-describing.

(4) Uddi:universal Description Discovery and integration is a unified description, Discovery and integration protocol. UDDI is also an architectural framework for Web services integration. It includes a standard specification of service description and discovery. The UDDI specification leverages many of the standards of the Consortium and Internet Engineering Task Organization (IETF) as its implementation base, such as extended Markup Language (XML), HTTP and Domain name Services (DNS) protocols. With it, our web services can register with the UDDI Center. For their customers to find use.

Web services are typically grouped into 4 categories:

(1) Business-oriented services (business-oriented Web Service): These services are geared towards enterprise application services;

(2) Customer-facing services (consumer-oriented Web Service): This service is for the original users of the Web site transformation, such as we can fully integrated in the Personal Finance Desktop system (call) on the Internet stock price query Web services, Ticket booking Web services, and so on, so that personal financial application of the automation level higher.

(3) Device-oriented services (device-oriented WEB Service): the use of such services is usually the terminal handheld devices and household appliances, such as palm, PocketPC, mobile phones and so on.

(4) System-oriented services (system-oriented Web Service): Some traditional system services, such as User authority authentication, system monitoring, etc., for example, all the online services of multinational enterprises can use the same user rights authentication Web services.

2.Web Service Advantages and disadvantages

Let's take a look at the disadvantages of the previous platform. Middleware platforms (RMI, Jini, CORBA, DCOM, etc.) provide a powerful service implementation tool, but these systems have a common flaw It is that they cannot be extended to the Internet: they require a tight coupling between the service client and the service itself, which requires a homogeneous basic structure. Cross-platform information exchange is not supported. In contrast, we find that Web Service has the following advantages:

(1) Cross-platform: WebService is completely based on XML (Extensible Markup Language), XSD (XmlSchema) and other platform independent software supplier standards;

(2) Self-description: Web service uses the WSDL standard language for self-describing, including complete information about the service's method \ parameter \ type \ return value.

(3) Modularization: Web Service is an application component that we can develop using any development platform and encapsulate it according to the module.

(4) Cross fire wall: Web service uses HTTP protocol to communicate, can traverse firewall.