1、企业级应用系统体系架构企业级应用系统体系架构（八）（八）SOA概述概述Chen HaopengFriday,January 06,20231The business drivers for a new approachnWhile IT executives have been facing the challenge of ncutting costsnmaximizing the utilization of existing technologynAt the same time they have toncontinuously strive to serve customers be
2、tternbe more competitivenbe more responsive to the businesss strategic priorities.nThere are two underlying themes behind all of these pressures:Heterogeneity and changeThe business drivers for a new approachnHeterogeneity nMost enterprises today contain a range of different systems,applications,and
3、 architectures of different ages and technologies.nIntegrating products from multiple vendors and across different platforms were almost always a nightmare.nBut we also cannot afford to take a single-vendor approach to IT,because application suites and the supporting infrastructure are so inflexible
4、.nChangenGlobalization and e-business are accelerating the pace of change.nImprovements in technology continue to accelerate,feeding the increased pace of changing customer requirements.The business drivers for a new approachnAs a result,business organizations are evolving nfrom the vertical,isolate
5、d business divisions of the 1980s and earliernto the horizontal business-process-focused structures of the 1980s and 1990sntowards the new ecosystem business paradigm.Business services now need to be componentized and distributed.nThere is a focus on the extended supply chain,enabling customer and p
6、artner access to business services.The business drivers for a new approachnQuestions:nHow do I make my IT environment more flexible and responsive to the ever changing business requirements?nHow can we make those heterogeneous systems and applications communicate as seamlessly as possible?nHow can w
7、e achieve the business objective without bankrupting the enterprise?nCurrently many IT executives and professionals alike believe that now we are getting really close to providing a satisfactory answer with service-oriented architecture.The business drivers for a new approachnIn order to alleviate t
8、he problems of heterogeneity,interoperability and ever changing requirements,such an architecture should provide a platform for building application services with the following characteristics:n Loosely coupledn Location transparentn Protocol independentnBased on such a service-oriented architecture
9、,a service consumer does not even have to care about a particular service it is communicating with because the underlying infrastructure,or service“bus”,will make an appropriate choice on behalf of the consumer.nThe infrastructure hides as many technicalities as possible from a requestor.Particularl
10、y technical specificities from different implementation technologies such as J2EE or.NET should not affect the SOA users.nWe should also be able to reconsider and substitute a“better”service implementation if one is available,and with better quality of service characteristics.Service-oriented design
11、nimportant service-oriented terminology:nServices:Logical entities,the contracts defined by one or more published interfaces.nService provider:The software entity that implements a service specification.nService consumer(or requestor):The software entity that calls a service provider.Traditionally,t
12、his is termed a“client”.A service consumer can be an end-user application or another service.Service locator:A specific kind of service provider that acts as a registry and allows for the lookup of service provider interfaces and service locations.Service broker:A specific kind of service provider t
13、hat can pass on service requests to one or more additional service providers.Interface-based designnIn both component and service development,the design of the interfaces is done such that a software entity implements and exposes a key part of its definition.nTherefore,the notion and concept of“inte
14、rface”is key to successful design in both component-based and service-oriented systems.nThe following are some key interface-related definitions:nInterface:Defines a set of public method signatures,logically grouped but providing no implementation.An interface defines a contract between the requesto
15、r and provider of a service.Any implementation of an interface must provide all methods.nPublished interface:An interface that is uniquely identifiable and made available through a registry for clients to dynamically discover.nPublic interface:An interface that is available for clients to use but is
16、 not published,thus requiring static knowledge on the part of the client.nDual interface:Frequently interfaces are developed as pairs such that one interface depends on another;for example,a client must implement an interface to call a requestor because the client interface provides some callback me
17、chanism.Interface-based designnThe following figure shows the UML definition of a customer relationship management(CRM)service,represented as a UML component,that implements the interfaces AccountManagement,ContactManagement,and SystemsManagement.nOnly the first two of these are published interfaces
18、,although the latter is a public interface.nNote that the SystemsManagement interface and ManagementService interface form a dual interface.Layered application architecturesnObject-oriented technology and languages are great ways to implement components.While components are the best way to implement
19、 services,though one has to understand that a good component-based application does not necessarily make an good service-oriented application.nThe term“the application edge”reflects the fact that a service is a great way to expose an external view of a system,with internal reuse and composition usin
20、g traditional component design.A closer look at service-oriented architecturenService-oriented architecture presents an approach for building distributed systems that deliver application functionality as services to either end-user applications or other services.It is comprised of elements that can
21、be categorized into functional and quality of service.A closer look at service-oriented architecturenFunctional aspects include:nTransport is the mechanism used to move service requests from the service consumer to the service provider,and service responses from the service provider to the service c
22、onsumer.nService Communication Protocol is an agreed mechanism that the service provider and the service consumer use to communicate what is being requested and what is being returned.nService Description is an agreed schema for describing what the service is,how it should be invoked,and what data i
23、s required to invoke the service successfully.nService describes an actual service that is made available for use.nBusiness Process is a collection of services,invoked in a particular sequence with a particular set of rules,to meet a business requirement.Note that a business process could be conside
24、red a service in its own right,which leads to the idea that business processes may be composed of services of different granularities.nThe Service Registry is a repository of service and data descriptions which may be used by service providers to publish their services,and service consumers to disco
25、ver or find available services.The service registry may provide other functions to services that require a centralized repository.A closer look at service-oriented architecturenQuality of service aspects include:nPolicy is a set of conditions or rules under which a service provider makes the service
26、 available to consumers.There are aspects of policy which are functional,and aspects which relate to quality of service;therefore we have the policy function in both functional and quality of service areas.nSecurity is the set of rules that might be applied to the identification,authorization,and ac
27、cess control of service consumers invoking services.nTransaction is the set of attributes that might be applied to a group of services to deliver a consistent result.For example,if a group of three services are to be used to complete a business function,all must complete or none must complete.nManag
28、ement is the set of attributes that might be applied to managing the services provided or consumed.SOA collaborationsnThe following figure shows the collaborations in a service-oriented architecture.The collaborations follows the“find,bind and invoke”paradigm.nA service consumer performs dynamic ser
29、vice location by querying the service registry for a service that matches its criteria.nIf the service exists,the registry provides the consumer with the interface contract and the endpoint address for the service.SOA collaborationsnThe roles in a service-oriented architecture are:nService consumer:
30、The service consumer is an application,a software module or another service that requires a service.It initiates the enquiry of the service in the registry,binds to the service over a transport,and executes the service function.The service consumer executes the service according to the interface con
31、tract.nService provider:The service provider is a network-addressable entity that accepts and executes requests from consumers.It publishes its services and interface contract to the service registry so that the service consumer can discover and access the service.nService registry:A service registr
32、y is the enabler for service discovery.It contains a repository of available services and allows for the lookup of service provider interfaces to interested service consumers.nEach entity in the service-oriented architecture can play one(or more)of the three roles of service provider,consumer and re
33、gistry.SOA collaborationsnThe operations in a service-oriented architecture are:nPublish:To be accessible,a service description must be published so that it can be discovered and invoked by a service consumer.nFind:A service requestor locates a service by querying the service registry for a service
34、that meets its criteria.nBind and invoke:After retrieving the service description,the service consumer proceeds to invoke the service according to the information in the service description.nThe artifacts in a service-oriented architecture are:nService:A service that is made available for use throug
35、h a published interface that allows it to be invoked by the service consumer.nService description:A service description specifies the way a service consumer will interact with the service provider.It specifies the format of the request and response from the service.This description may specify a set
36、 of preconditions,post conditions and/or quality of service(QoS)levels.SOA collaborationsnIn addition to dynamic service discovery and definition of a service interface contract,a service-oriented architecture has the following characteristics:nServices are self-contained and modular.nServices suppo
37、rt interoperability.nServices are loosely coupled.nServices are location-transparent.nServices are composite modules,comprised of components.nThese characteristics are also central to fulfilling the requirements for an e-business on demand operational environment.Finally,service-oriented architectur
38、e is not a new notion.Services ponentsnA service is a coarse-grained processing unit that consumes and produces sets of objects passed-by-value.nIt is not the same as an object in programming language terms.Instead,it is perhaps closer to the concept of a business transaction such as a CICS or IMS t
39、ransaction than to a remote CORBA object.nA service consists of a collection of components that work in concert to deliver the business function that the service represents.nThus,in comparison,components are finer-grained than services.nIn addition,while a service maps to a business function,a compo
40、nent typically maps to business entities and the business rules that operate on them.nAs an example,let us look at the Purchase Order component model for the WS-I Supply Chain Management sample.Services ponentsnIn a component-based design,components are created to closely match business entities(suc
41、h as Customer,Purchase Order,Order Item)and encapsulate the behavior that matches the entities expected behavior.nPurchase Order component provides functions to obtain information about the list of products ordered and the total amount of the ordernItem component provides functions to obtain informa
42、tion about the quantity and price of the product ordered.In a service-oriented design,services are not designed based on business entities.Instead,each service is a holistic unit that manages operations across a set of business entities.For example,a customer service will respond to any request from
43、 any other system or service that needs to access customer information.The customer service can process a request to update customer information;add,update,delete investment portfolios;and enquire about the customers order history.The customer service owns all the data related to the customers it is
44、 managing and is capable of making other service inquiries on behalf of the calling party in order to provide a unified customer service view.This means a service is a manager object that creates and manages its set components.Service-oriented architecture benefitsnWith a service-oriented architectu
45、re,we can realize several benefits to help organizations succeed in the dynamic business landscape of today:nLeverage existing assets.nEasier to integrate and manage complexity.nMore responsive and faster time-to-market.nReduce cost and increase reuse.nBe ready for what lies ahead.nService-oriented
46、architecture is by no means a silver bullet,and migration to SOA is not an easy task.Rather than migrating the whole enterprise to a service-oriented architecture overnight,the recommended approach is to migrate an appropriate subset of business functions as the business need arises or is anticipate
47、d.SOA的疑问n在我的系统中，所有的功能都包装成了Web Service，现在我的系统是否就是SOA架构了？n协议独立、位置透明、松散耦合n高度动态性SOA的疑问nServices 与 Components的差异是什么？n问题域 vs.解决域n集成方式n我们的机遇863计划信息技术领域2007年度专题课题申请指南（节选）n专题一：智能感知与先进计算技术专题What is Software Architecturen探索导向类课题n8服务计算技术n主要研究内容（可从以下内容中选择其一申请课题）：（1）服务描述与发现、可信的服务资源组织与管理；（2）可靠的服务组合方法与验证；（3）动态的服务组合
48、。n说明与要求：要求完成相应的软件原型系统；获得软件著作权和申请专利，或以开放源码形式发布。Models of SOADnJBI（Java Business Integration）n2005.8 JSR 208n为JBI组件（包括服务引擎和绑定组件）的开发者建立一套标准的服务提供者接口SPI。n抽象的协议无关的消息交换和规格化消息。n提供一套标准的JBI组件间消息交换机制。n建立一个标准来封装JBI组件，并为这些组件部署服务。n定义一些管理监控挂钩（hooks），用于以后开发针对各种特定问题域的标准工具。n提供服务引擎和绑定组件实现的复杂性和多样性。允许不同的供应商发布JBI组件，这些组件之
49、间能够可靠地互操作，由这些组件（在JBI基础设施之上）构建的系统可以集中管理。28Models of SOADnJBI（Java Business Integration）29Models of SOADnSCA(Service Component Architecture)/SDO(Service Data Object)nSCA定义了如何创建服务组件以及如何将服务组件组装成业务解决方案的通用方法。nSCA由一系列规范组成,包括n说明如何用某种具体语言（如Java、C+、Spring、BPEL等）实现业务服务组件的组件实现(Component Implementation)规范；n如何定义组
50、合服务组件结构的装配(Assembly)模型；n如何使用各种访问方法（如Web services、JMS、RMI-IIOP、REST等）的绑定(Binding)规范；n如何将基础设施服务（如安全、事务、可靠消息等）加到解决方案的策略框架(Policy Framework)nSDO(Service Data Object)n提供了一种通用的数据编程架构和API，SCA组件可以通过传递服务数据对象来交换数据。nSDO 体系结构中的基本概念主要有数据对象（Data Object）、数据图（data graph）和数据访问服务DAS(Data Access Services)。30Models of
