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Web Service技术简介 　　　　摘　　要 动机 概述：是什么、做什么？ 体系结构：组件与操作 主要 SOAP WSDL UDDI Web Service安全 主要开发工具 主要研究内容 参考文献 动机Motivation 构建应用 包含来自 cnn.com的天气预报; 包含每日股票报告; 包含来自 google map的谷歌地图; 包含来自 xe.com的汇率 … 过去，我们使用屏幕HTML抓取 screen/html scraping获取信息 不可靠 抽取和维护数据十分困难 解决: web service 每个网站提供了可编程的接口 什么是 web service Web Service 可在网络，一般地，Web上被描述、出版、定位和调用的自包含的、模块化的应用 Web services are self-contained, modular applications that can be described, published, located and invoked over a network, generally, the Web -IBM. 什么是Web 服务（Cont.） A web service is a software system designed to support interoperable machine-to-machine interaction over a network. It has an interface described in a machine-processable format (specifically WSDL). Other systems interact with the Web service in a manner prescribed by its description using SOAP messages, tipically conveyed using HTTP with an XML serialization in conjunction with other Web-related standards --W3C definition 什么是Web服务（Cont.） Web services are Web-based applications composed of coarse-grained business functions accessed through the Internet --“Computer” - IEEE Computer Society Journal 什么是Web service （Cont.） Self-contained, modular business applications that have open, internet-oriented, standard based interfaces — UDDI Consortium Web service （Cont.） a software application identified by a URI, whose interfaces and bindings are capable of being defined, described, and discovered as XML artifacts. A web service supports direct interactions with other software agents using XML-based messages exchanged via Internet-based protocols. --W3C Web service （Cont.） a standardized way of integrating Web-based applications using the XML, SOAP, WSDL, and UDDI open standards over an Internet protocol backbone. XML is used to tag the data, SOAP is used to transfer the data, WSDL is used for describing the service available, and UDDI is used for listing what services are available --Webopedia 什么是Web Service （Cont.） 一个 Web 服务就是一个应用程序，它可以通过轻量级的、与厂商无关的通信协议从其他的系统跨网络（Internet 或者 Intranet）接受 XML 格式的调用请求 基于XML的一种分布式计算技术、一种中间件技术 一种松散耦合的、面向服务的架构 在这种面向服务的架构中，接口的定义是至关重要的。正是接口定义（通常由 WSDL 来表达）作为服务所提供的东西和客户端所期望的结果之间的合约。 为了确保参与的各方是松散耦合的，必须同意两个关键的事项：共同的通信格式（也就是消息的样式）和共同的协议（也就是消息如何到达）。 最常见的组合是通过 HTTP（协议）的 SOAP （格式）。 什么是Web Service（Cont.） 一个 Web 服务是一个接受 XML 格式请求的应用程序 无论一个远程函数调用是否作用于 Web 服务，或者一个消息是否发送给它，都必须用 XML 标记封装请求。 从其他系统跨网络（Internet 或者 Intranet） Web 服务类似于其他分布式计算技术，使远程、分布式企业应用程序成为可能。例如DCOM、CORBA等，实际上可以认为Web服务是分布式技术的发展。 Web 服务堆栈的平台的互操作性 这种互操作性是使得 Web 服务对于 EAI 如此具有吸引力的关键特征。 什么是Web Service（Cont.） 轻量级 Web 服务所依赖的技术和协议被得相当轻量级的，将许多复杂的特征，比如安全性，会话处理和事务处理，都留给 Web 服务的扩展来处 与厂商无关的通信协议 因为 Web 服务是基于的开放协议， Web 服务系统提供了跨越所有厂商，实现了异构系统的互操作 什么是Web服务 另外一个例子 (vertical integration) 旅游网站接受客户订单，向旅店网站发送消息，预订房间，并通知客户. A travel Web site that takes a reservation from a customer, and then sends a message to a hotel application, accessed via the Web, to determine if a room is available, books it, and tells the customer he or she has a reservation is an example of a Web Services application Web Service 特性 良好的封装性 Web Service implementation is invisible to entities outside the service Exposes an interface but hides details 松散耦合 Service and consumer software can be redesigned independently Messages are decoupled from the data transport, and are easy to integrate with other platforms and open standards technology. Changing the implementation of one component does not require changing the rest of the services, which makes configuration and deployment easier to manage. 自描述. 分布式 基于开放标准 为什么 Web Service “Just as the web revolutionized how users talk to applications, XML transforms way applications talk to each other” —Bill Gates 为什么 Web Service “Web services will be bigger than Java or XML”. – Rod Smith, VP of Emerging Technology, IBM “Web services are expected to revolutionize our life in much the same way as the internet has during the past decade or so.” —Gartner “By 2004, 40% of the financial services transactions and 35% of online government services will be web service-based.” –Gartner 计算三定律 Moore's Law Computing power doubles every 18 months Gilder's Law Network bandwidth capacity doubles every 12 months Metcalfe's Law (Net Effect) Value of network is proportional to the square of the number of users of the system (n2). Web services greatly increase network value Web服务可以做什么 让任何平台上的用任何语言编写的服务进行交互 将应用程序功能概念化成任务（服务），从而形成面向任务的开发和工作流。这使得更抽象的软件能够为工作在业务层面具有较少软件分析技术的用户所用 允许松耦合，这意味着，每当其中某个或多个服务在设计或实现中发生变更时，服务应用程序之间的交互可能不会因此而中断 使现有的应用程序能适应变化中的业务条件和客户需要 Web服务可以做什么（Cont.） 向现有或遗留的软件应用程序提供服务接口，而无需改变原来的应用程序，从而使这些应用程序完全可以运行在这种服务环境下 引入其他一些与原有功能无关的管理或操作管理功能，比如可靠性、可计帐性和安全性等等，从而在业务计算环境中增加了其通用性和实用性 典型应用 组件化电子服务（Componentized E-Services）（B2B） 企业应用集成（Enterprise Application Integration，EAI） 企业内部组件重用（Intra-enterprise component reuse Intra-enterprise） Web服务体系结构－组件 服务提供者 提供服务及维护注册表以使服务可用； 代理 服务提供者与服务请求者的中介； 传统的代理是UDDI注册中心； 服务请求者 发现 Web 服务，然后调用这些服务以创建应用程序 服务 应用程序，通过服务描述语言进行描述，其描述信息通过代理发布 具体的 SOA UDDI Registry WSDL Web Service Provider SOAP Service Consumer Points to description publish Describes Service Finds Service Communicates with XML Messages Web服务体系结构－操作 发布／撤除发布（Publish） 发布和撤除发布是指将服务发布至代理处（发布）或除去它们的一些项（撤除发布）。服务提供者通过代理来发布或不发布某个服务。 查找 （Find）， 查找操作由服务请求者和服务代理共同完成。服务请求者描述他们正在寻找的服务类型，而服务代理发布与请求最匹配的结果。 绑定 （Bind） 绑定操作发生在服务请求者和服务提供者之间。双方经过适当的商讨之后，请求者就可以访问和调用提供者所提供的服务。 Web服务实现过程 Web Services Architecture W3C Working Group Note 11 February 2004 整个实现过程基本上分为四步 在这个过程中代理发挥着重要的作用 Web服务实现过程 请求者和提供者互相认识 请求者和提供者在服务描述和语义上达成一致 通过请求者agent和提供者agent实现 请求者和提供者agent交换消息，代表请求实体和供应商执行任务 the requester and provider entities become known to each other (or at least one becomes know to the other) the requester and provider entities somehow agree on the service description and semantics that will govern the interaction between the requester and provider agents the service description and semantics are realized by the requester and provider agents the requester and provider entities become known to each other (or at least one becomes know to the other) the requester and provider entities somehow agree on the service description and semantics that will govern the interaction between the requester and provider agents the service description and semantics are realized by the requester and provider agents the requester and provider agents exchange messages, thus performing some task on behalf of the requester and provider entities. （I.e., the exchange of messages with the provider agent represents the concrete manifestation of interacting with the provider entity's Web service.） Web Services Architecture W3C Working Group Note 11 February 2004 “Known each other” 发现服务，将发现本身作为一个服务 发现服务获取WSD及FD 请求者实体向发现服务提供选择WEB服务的信息 发现服务返回符合标准的WSD Web Services Architecture的思考 Agent Requester Agent and Provider Agent; 传统的注册中心被代理替代； 发现服务（Discovery Service） 执行一个发现的过程。获取WSD和FD、请求者实体提出发现标准、返回WSD 可以人工发现也可以自动发现（Agent）； 发现的途径 注册中心； 索引； P2P发现； IBM Conceptual Web services stack Service Flow Service Discovery Service Publication Service Description XML–Based Messaging Network WSFL Static -> UDDI Static -> UDDI WSDL SOAP HTTP, FTP, email, etc. Security Management Quality of Service XML–Based messaging Exchange structured data between network applications Allows software running on disparate operating systems, and environments to make RPCs Simple Object Access Protocol (SOAP) W3C standard Built over XML Web Services 开发 Microsoft Visual Studio .NET Eclipse IDE with WSDK … 主要研究内容 工业界 Web服务规范及协议标准化问题； SOAP、WSDL、UDDI、WS-Security等； 学术界 数据集成，通过一定的访问控制及事务机制保证服务响应的可靠性及服务组件的协同工作； 服务搜索与发现，如P2P、自动化、基于语义； 服务组合问题 现有安全策略与Web服务集成的问题； Web服务与其它网络技术的结合，例如P2P、网格； 特别说明：把握未必准确 Web service 工程 高度灵活和敏捷的软件，应能适应业务变化 传统的软件工程方法不适用 新问题 信任和信心（Trust and confidence） 风险，责任和恢复（Risk, responsibility, recovery ） 个性化 e-Services (1) From Wikipedia, the free encyclopedia e-Service is a term usually referring to the provision of services provided via the Internet (the prefix 'e' standing for "electronic", as it does in many other uses) e-Service includes "e-commerce", although it may also include non-commercial services Non-ecommerce e-Services include (at least some) "eGovernment" services From an article written by C.Peraire and D.Coleman An e-Service is some interaction offered to a user, across the Internet, that has meaning and economic value An e-Component is a software module that provides one or more e-Services. Thus, the e-Services provided by an e-Component constitute its interface e-Services (2) E-services is a business concept developed by Hewlett Packard (HP) HP e-Services integration platform “… There are essentially no constraints on what the platform can aggregate into the portal – Web-enabled applications and informations stores, legacy applications, and applications on open client/server systems …” Using HP's e-services concept, any application program or information resource is a potential e-service; Internet Service Providers (ISPs) and other companies are logical distributors or access points for such services Cisco e-Services “…Cisco eServices provides a variety of voice processing for your Cisco IP Telephony implementation…” Cisco IP Integrated Voice Response (Cisco IP IVR) Cisco IP Integrated Contact Distributor (Cisco IP ICD) e-Services (conclusions) The word e-Service: has a very general meaning is used to represent all web-based applications In some environments Web services can be considered as e-Services References (1) “Web Services Computing: Advancing Software Interoperability” “Computer” IEEE Computer Society Journal October 2003 (Jen-Jao Chung, Kwei-Jay Lin, Richard G. Mathieu) “Turning Software into a Service” “Computer” IEEE Computer Society Journal October 2003 (Mark Turner, David Budgen, Pearl Brereton) “Web Services architecture overview” IBM Web Services Architecture Team - September 2000 - http://www-106.ibm.com/developerworks/web/library/w-ovr/ “Web Services Conceptual Architecture (WSCA 1.0)” Heather Kreger – IBM Software Group – May 2001 - www-306.ibm.com/software/solutions/webservices/pdf/WSCA.pdf “Web Services Architecture” – W3C Working Group – February 2004 – (David Booth, Hugo Haas, Francis McCabe, Eric Newcomer, Michael Champion, Chris Ferris, David Orchard) – http://www.w3.org/TR/2004/NOTE-ws-arch-200040211/ References (2) “Web Services Architectures” – Tect – Judith M. Myerson “Service-Oriented Architecture expands the vision of Web services, Part 1” – IBM Corporation – Mark Colan – www-106.ibm.com/developerworks/ library/ws-soaintro.html “Service-Based Software: The Future for Flexible Software” – Keith Bennett, Paul Layzell, David Budgen, Pearl Brereton, Linda Macaulay, Malcolm Munro “Modeling for E-Service Creation” Cecile Peraire and Derek Coleman “Semantic Web services and Web services standards” – Sinuhé Arroyo, Christoph Bussler and Rubén Lara – EEE04 – http://deri.semanticweb.org/ “Component-Based Software Engineering” – Wilhelm Hasselbring “Cisco eServices Architecture – Cisco IPCC Express Edition” Cisco Systems – http://www.cisco.com/en/US/products/sw/custcosw/ps1846/products_administration_guide_chapter09186a00900eeac8.html 主要参考文献 http://www.w3.org/2002/ws/ http://www.w3.org/TR http://www-128.ibm.com/developerworks/cn/webservices http://www.microsoft.com/china/MSDN/library/WebServices/default.mspx?mfr=true http://www.webservices.org http://www.uddi.org CNKI、万方学位论文数据库等 http://webservices.sys-con.com/(SOA Web Services Journal) http://www.web2journal.com http://www-128.ibm.com/developerworks/webservices/standards/ A travel Web site that takes a reservation from a customer, and then sends a message to a hotel application, accessed via the Web, to determine if a room is available, books it, and tells the customer he or she has a reservation is an example of a Web Services application the requester and provider entities become known to each other (or at least one becomes know to the other) the requester and provider entities somehow agree on the service description and semantics that will govern the interaction between the requester and provider agents the service description and semantics are realized by the requester and provider agents the requester and provider entities become known to each other (or at least one becomes know to the other) the requester and provider entities somehow agree on the service description and semantics that will govern the interaction between the requester and provider agents the service description and semantics are realized by the requester and provider agents the requester and provider agents exchange messages, thus performing some task on behalf of the requester and provider entities. （I.e., the exchange of messages with the provider agent represents the concrete manifestation of interacting with the provider entity's Web service.）