Transcript 面向服务概述
冯志勇 天津大学计算机学院 2008年10月 SOA的定义及其商业和技术价值 面向服务 vs. 面向对象 面向服务的架构 vs. 分布式对象架构 正像上个世纪的对象似的, 服务是一个很酷 的时髦词，但是，今天SOA是一个经常被 人错误地理解的话题. “My architect thinks it’s service-oriented, my developers insist it’s object-oriented, and my analysts wish it would be more business-oriented. All I can tell you is that it isn’t what it was before we started building Web services.” 对不同的人，服务的含义不同: ◦ 松耦合的软件构件，它们相互通过标准的 Internet技术动态的交互 (Gartner). ◦ 一个有URI识别的软件应用，它的接口和 绑定能够通过XML制品被定义、描述和发 现，并且支持采用基于满足Internetbased protocolsXML消息机制与其它应 用交互A (W3C). ◦ 通过Internet使用开发标准的一段商业逻 辑 (Microsoft). ◦ 通过Web上标准协议提供的，封装好的、 松耦合的、契约化的软件功能 (DestiCorp). ◦ 服务独立于应用程序和运行计算平台的是 自包含的、可重用得软件模块，它有定义 良好的接口，并允许业务任务和需要执行 任务的具体IT构件 1:1 影射。 SOA的定义仍在发展变化. ◦ 一组能够被调用的构件,并且其接口描述能够被 发布和发现 (W3C). ◦ SOA是一种client/server 设计方法，其中的应 用程序由软件服务和软件服务消费者组成 (also known as clients or service requesters). SOA 不同于一般的client/server 模式，其定义 强调软件构件中的松耦合，并且采用分离的接 口 (Gartner). ◦ SOA是一个业务驱动的IT架构方法，它可以把 业务集成为连接的可重复的商业任务或服务. SOA使得 IT系统能够快速、容易和经济的适应 业务需求的迅速改变，从而有助于今天的业务 创新. SOA协助客户增强他们业务过程的灵活性， 强化了其底层基础结构，通过在不同的应用和 信息资源之间建立连接重用其原有的IT 投资。 (IBM) A New Way of Thinking Take a CD for instance. If you want to play it, you put your CD into a CD player and the player plays it for you. The CD player offers a CD playing service. Which is nice because you can replace one CD player with another. You can play the same CD on a portable player or on your expensive stereo. They both offer the same CD playing service, but the quality of service is different. 2015/7/20 8 The SOA Story Application 1 Application 2 Business Process Auto-searchable Found Service broker Services Registration Registration Registration Component Library Organization X Organization Y Organization Z 2015/7/20 9 Research & Development Marketing Distributed Data Distributed Computation Distributed users ….. Research & Development Marketing Accounting Customer Service Manufacturing Accounting Sales Customer Service Manufacturing Sales 2015/7/20 10 – 互操作问题 – 异构的网络协议 – 异构的硬件平台 – 异构的操作系统 – 异构的应用程序格式…… There must be consensus On 互操作性! 2015/7/20 11 Changing Market Dynamics On Demand Static Business Technology Business process decision-making Fixed Costs Rigid organizational structure Proprietary systems Slow and steady economic growth Labor-intensive Long-term product lifecycle Users adapt to technology Passive operational risk management Collaborative, integrated value nets Variable costs Dynamic, adaptive, learning Open, integrated systems Unpredictable fluctuations Self-healing, self-managing system Shortening product lifecycle Technology adapts to users Proactive risk management Increased focus on privacy and security 2015/7/20 12 2015/7/20 13 新机遇 节约成本 敏捷业务 ◦ 产品创新和服务从关键的特色赢得竞争优势. ◦ 传统技术适应新商业模型的能力，从而使更多的渠道来获得收入。 ◦ 通过削减整体花费降低成本。 ◦ 由于恶性竞争，每一个错过的商业机会的企业职位低于其竞争对手。 有能 力的企业能够快速应对各种业务的刺激将是关键的生存。 ◦ 更快的上市时间，提高客户满意度，还客户的忠诚度。这样的结果是增加 了商业和更高的收入。 ◦ 能够提供按需服务，实时24 / 7 。 ◦ 无缝协作的合作伙伴和客户有助于提高服务质量和上市时间。 2015/7/20 14 使得互操作成为IT应用的固有特征. 提供了一个 time-to-market 快 速方法 快速响应业务条件变化 降低了重复性工作，最大化已存在 系统的价值 2015/7/20 15 开放Openness ◦ 对一个组织而言，依赖于它几乎无法控制外部技术和平台供应商是 危险的。然而，采用开放的标准减轻这一风险。 节约成本Cost Saving ◦ 减少维护费用 ◦ 增加重用IT投资，以提高生产力，从而提高投资回报率（ROI）. 敏捷Agility ◦ 松耦合增加应用的灵活性，并降低新的应用程序产品上市时间。 ◦ 无缝的可扩展性以最低成本，以满足季节性增加负荷。 2015/7/20 16 软件体系结构设计原则 ◦ ◦ ◦ ◦ 抽象 关注点分离 预期变化 设计重用 2015/7/20 17 Enterprise Integration Object Oriented BPM SOA CBSD Web Application Distributed Computing CBSD: Component-Based Software Development BPM: Business Process Management 2015/7/20 18 Distributed Computing Client/Server WSDL CORBA NFS VT3270 MQ RPC EJB VT100 EAI SOAP TCP/IP WWW Program Paradigm COBOL SOA Stored Procedure Modular2 Pascal Smalltalk Java PROLOG Ada SIMULA Assembler 1950 1960 1970 C# C++ 1980 1990 2000 2015/7/20 19 基于开放标准 鼓励固有的内在重用 鼓励强调互操作性的 可扩展性 根本上自主 促进动态发现 促进架构的组合性 促进整个企业松散耦合 支持逐步实施 2015/7/20 20 Improved Integration, intrinsic interoperability Inherent reuse Streamlined architectures and solutions Leveraging the legacy investment Establishing standardized XML data representation Focused investment on communications infrastructure Best-of-breed alternatives Organizational agility 2015/7/20 21 The business drives the services, and the services drive the technology. Business agility is a fundamental business requirement. A successful SOA is always in flux. 2015/7/20 22 W3C OASIS WS-I Established 1994 1993 as SGML Open, 1994 as OASIS 2002 Approximate membership 400 600 200 SOA goal To further the evolution of the Web, by providing fundamental standards that improve online business and information sharing. To promote online trade and commerce via specialized Web services standards. To foster standardized interoperability using Web services standards. SOA deliverables XML, XML Schema, XQuery, XML Encryption, XML Signature, XPath, XSLT, WSDL, SOAP, WSCDL, WS-Addressing, Web Services Architecture UDDI, ebXML, SAML, XACML, WS-BPEL, WSSecurity Basic Profile, Basic Security Profile 2015/7/20 SOA Standards Organizations 23 几个面向服务的原则源自面向对象的原则 一些面向对象的原则，如继承权，不符合面向服 务的世界。 一些面向服务的原则，如松耦合和自主，不直接 来自面向对象。 ◦ ◦ ◦ ◦ ◦ abstraction Encapsulation Interface first Composition Statelessness -- decomposition -- Reusability -- Loose coupling -- Autonomy -- Discoverability 2015/7/20 25 Service-Orientation Loose coupling between units of processing logic. Object-Orientation Based on predefined class dependencies, resulting in more tightly bound objects. oarse-grained interfaces (service description) Fine-grained interfaces (APIs), Communicatio Message-based communication based on RPC or local API calls. Large unit of processing logic (service), Unit of logic (object) tend to be smaller and May vary significantly in scope. More specific in scope. Promotes the creation of activity-agnostic Encourages the binding of processing logic units of processing logic (services) that are with data, resulting in highly intelligent driven into action by intelligent units of units (object). communication (message). efers that units of processing logic (services) Promotes binding of data and logic, resulting designed to remain as stateless as possible. In the creation of more stateful units (objects 2015/7/20 26 Programming Language Object-Oriented Concept & Architecture Simula Smalltalk Objective C C++ Java Standard Specification Service-Oriented Concept & Architecture XML UDDI ebXML WSDL SOAP OWL Modeling UML Modelin g BPEL WSFL XLANG Technology & Methodology OOAD OO Framework OODB OO Process model Technology & Methodology MDA SO Framework Ontology / Service DB SO lifecycle process 2015/7/20 27 SOA彻底背离客户服务器结构。目前SOA仍采用 一些最初用于建立客户机服务器应用程序的技术。 引入SOA更为复杂，与简单的两层客户机服务器 架构形成鲜明对比 分布式互联网架构有许多共同之处与SOA ，其中 包括大量的技术。然而， SOA有鲜明的特色有关 技术和它的基本设计原则。 2015/7/20 29 Two Tier with Thin Client Two Tier with Fat Client Client Client Client Data Management Application Processing Presentation Application Processing Presentation Three Tier Server Presentation Server Data Management Server Server Application Processing Data Management 2015/7/20 30 RPC-based Remote Object based Web based ◦ Client and middleware server is tightly coupled ◦ Remote objects communicates through standard interface languages ◦ Object models: OMG CORBA, SUN Java RMI, MS DCOM ◦ Browser + “Dynamic content generation” ◦ Enabling techniques: CGI, Java Servlet/JSP, MS ASP 2015/7/20 31 Coupled with a powerful communications infrastructure, distributed objects divide monolithic client/server applications into self-managing components, or objects, that can interoperate across disparate networks and operating systems. ◦ SUN J2EE JavaTM 2 Platform, Enterprise Edition ◦ MS DCOM Distributed Component Object Model ◦ OMG CORBA Common Object Request Broker Architecture 2015/7/20 32 In a distributed computing system, middleware is defined as the software layer that lies between the operating system and the applications on each site of the system. It serves to "glue together" or mediate between separate components. Objectives Examples ◦ ◦ ◦ ◦ Hiding distribution Hiding the heterogeneity Providing uniform, standard, high-level interfaces Supplying a set of common services ◦ Transaction processing monitors ◦ Data converters ◦ Communication controllers 2015/7/20 33 Design Challenges ◦ ◦ ◦ ◦ ◦ Performance Scalability Complexity of administration Mobility and dynamic reconfiguration Global information network to manage large applications that are heterogeneous, widely distributed and in permanent evolution 2015/7/20 34 OMG Standard, “to allow applications to communicate with one another no matter where they are located or who has designed them” ◦ 1991, CORBA 1.1, IDL & API within an ORB ◦ 1994, CORBA interoperability & IIOP (Internet InterORB Protocol) ◦ 2002, CORBA Component Model 2015/7/20 35 Distributed object computing middleware that shields applications from heterogeneous platform dependencies. To simplify development of distributed applications by automating/encapsulating ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ Object location Connection & memory mgmt. Parameter (de)marshaling Event & request demultiplexing Error handling & fault tolerance Object/server activation Concurrency Security CORBA defines interfaces, not implementations 2015/7/20 36 Object Request Broker: enables objects to transparently make and receive requests and responses in a distributed environment. ◦ The core of the reference model, “telephone exchange” Object Services: a collection of services (interfaces and objects) that support basic functions for using and implementing objects. ◦ e.g. Naming, Trading, and Life Cycle Service Common Facilities: a collection of services that many applications may share, but which are not as fundamental as the Object Services ◦ e.g. e-mail facility Application Objects: products of a single vendor on in-house development group that controls their interfaces. 2015/7/20 37 Application Objects Domain Facilities Horizontal CORBA Facilities Object Request Broker Domain Facilities 2015/7/20 38 Interface Repository IDL Compiler Client Dynamic Invocation ORB Core IDL Stub Implementation Repository Object ORB Interface IDL Dynamic Skeleton Skeleton Object Adapter GIOP/IIOP/ESIOPS 2015/7/20 39 A logical set of services ◦ Locates the remote object, communicates the request, waits for the results and when available communicates the results back to the client ◦ Location transparency ◦ Programming language independent: interface translation and language binding Client Object Object Request Broker (ORB) 2015/7/20 40 Language neutral, Language mapping ◦ ◦ ◦ ◦ Modularized object interface Operations and attributes that an object supports Exceptions raised by an operation Data types of an operation return value, its parameters, and an object’s attributes Client Object IDL Stub IDL Skeleton Object Request Broker (ORB) 2015/7/20 41 Activate server Implementation 1S Repository In args Client Obj. ref. 1C Return Control to Client Wait for request to complete 4C IDL Stub 3C 2 C Operation () Out args + return value Locate target object Return Request Send request to server Object IDL Skeleton 4S 2S 3S Process Request Activate Object’s Servant ORB CORE 2015/7/20 42 动机 ◦ ORB implementation diversity ◦ ORB boundaries: Partition the environment into different ORBs Simplified test, management, and maintenance Decentralized control e.g. internet ORB, company ORB ◦ ORB vary in scope, distance and lifetime e.g. archives ORB, game ORB 单元 ◦ Inter-ORB Bridge: transactions between ORB domains ◦ General Inter-ORB Protocol (GIOP): ORB-ORB interactions over connection-oriented transport protocol ◦ Internet Inter-ORB Protocol (IIOP): ORB-ORB communication across the Internet (TCP/IP) 2015/7/20 43 Client Object Client IDL Stub IDL Skeleton IDL Stub ORB 1 IIOP Object IDL Skeleton ORB 2 Interoperability uses ORB-to-ORB communication 2015/7/20 44 Services Description Object Life Cycle Define how CORBA objects are created, removed, moved and copied Naming Define how CORBA objects can have friendly symbolic names Events Decouple the communication between distributed objects Relationships Provides arbitrary typed n-ray relationships between CORBA objects Externalization Coordinates the transformation of CORBA objects to and from external media Transactions Coordinates atomic access to CORBA objects Concurrency Control Provides a locking service for CORBA objects in order to ensure serialized access Property Supports the association of name-value pairs with CORBA objects Trading Supports the finding of CORBA objects based on properties describing the services offered by the object Query Support queries on objects 2015/7/20 45 A platform for developing applications ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ Oct. 1994, Public introduction of Java Jan. 1996, JDK 1.0 released Apr. 1997, EJB specification announced Dec. 1998, Java 2, SDK 1.2 released Jun. 1999, J2EE announced Dec. 1999, J2EE platform released Sep. 2001, J2EE 1.3 released Nov. 2003, J2EE 1.4 released 2015/7/20 46 J2EE Application Architecture Client Side Presentation Server Side Presentation Server Side Business Logic Browser Web Server JSP EJB Contain er EJB JSP EJB Java Application Java Servlet EJB Other Device J2EE platform J2EE platform Pure HTML Java Applet Enterprise Information System Desktop J2EE Client 2015/7/20 47 2015/7/20 48 2015/7/20 49 HTTP/HTTPS JAAS – Java Authorization and Authentication Service JTA – Java Transaction API JNDI – Java Naming and Directory Service RMI-IIOP JDBC – Java DataBase Connectivity JMS – Java Message Service JavaMail JAXP – Java API for XML Parsing Java IDL …… 2015/7/20 50 It allows the system designer to delay decisions on where and how services should be provided It is a very open system architecture that allows new resources to be added to it as required The system is flexible and scaleable It is possible to reconfigure the system dynamically with objects migrating across the network as required 2015/7/20 51 紧耦合 自有 ◦ Both ends of each distributed computing link had to agree on the details of the API. A code change to a COM object, for example, required corresponding changes to the code accessing that object. ◦ Microsoft controlled DCOM ◦ Implementing a CORBA architecture typically necessitated the decision to work with a single vendor's implementation of the specification. 2015/7/20 52 SOA is developed upon the weaknesses of distribute object computing technique. ◦ 基于标准 Reliance upon universally accepted standards provides broad interoperability among different vendors’ solutions ◦ 松耦合 Separates the participants in distributed computing interactions so that modifying the interface of one participant in the exchange does not break the other. 2015/7/20 53 SOA通过松耦、满足标准的互联网协议可重用的 软件组件合动态协作。 SOA是业务和技术需求驱动的，即，开放性的合 作，节约成本和动态的变化灵活性。 SOA来自其它软件技术，包括分布式对象计算， 基于构件的软件工程和企业应用集成 2015/7/20 54 M. P. Singh and M. N. Huhns, “Service-Oriented Computing”, John Wiley & Sons, 2005. Thomas Erl, “Service-Oriented Architecture: Concepts, Technology, and Design”, Prentice Hall, 2005. Eric Newcomer and Greg Lomow, “Understanding SOA with Web Services”, Addison Wesley, 2005. D. Krafzig, K. Banke and D. Slama, “Enterprise SOA: Service-Oriented Architecture Best Practice”, Prentice Hall, 2005. Wei-Tek Tsai, “What is SOA? Why should you care?”, Tsinghua University Short Course on ServiceOriented Computing and Architecture, 2006. Jen-Yao Chung, “Service-Oriented Architecture and Web Services”, keynote speaking, SOSE 2005. 2015/7/20 55 Jason Bloomberg, “Principles of SOA”, Feb. 2003. “A Practical Guide to SOA for IT Management”, Systinet Corp. 2005. Shireesh Jayashetty, Pradeep Kumar M, “Adopting Service Oriented Architecture increases the flexibility of your enterprise”, Infosys, 2006. Ian Summerville, “Software Engineering” (6th Edition), Addison-Wesley, 2000. ObjectWeb, http://middleware.objectweb.org/ OMG, http://www.omg.org/ Doug Schmidt’s CORBA page, http://www.cs.wustl.edu/~schmidt/corba.html IBM SOA glossary, http://www306.ibm.com/software/solutions/soa/glossary/ind ex.html 2015/7/20 56