SA02.2 Style 调用返回 仓库

1SE3121021:SoftwareArchitecture

SoftwareArchitectureStyle

2SoftwareArchitectureStyle:Call/Return

调用/返回

3Call/Return的不同种类Mainprogramandsubroutines主程序和子程序Classicalprogrammingparadigm-functionaldecompositionObject-Oriented/AbstractDataTypesInformation(representation,accessmethod)hidingLayeredhierarchiesEachlevelonlycommunicateswithitsimmediateneighborsOtherClient/Server……4HistoryMainprogramandsubroutines单线程控制，划分为若干处理步骤Functionalmodules把处理步骤集成到模块内AbstractDataTypes操作和数据捆绑在一起，隐藏具体实现Objects方法（动态绑定），多态（子类），重用（继承）OOArchitectures对象活动在不同的进程/线程Client/Server,tieredstylesComponents多个接口，二进制兼容，中间件也是编程语言的发展历程5MainProgramandSubroutine思考：此图为有向图，是否可能出现环？6MainProgramandSubroutineProblem:Thispatternissuitableforapplicationsinwhichthecomputationcanappropriatelybedefinedviaahierarchyofproceduredefinitions.存在层次结构Context:Manyprogramminglanguagesprovidenaturalsupportfordefiningnestedcollectionsofprocedures（过程的嵌套）andforcallingthemhierarchically.Theselanguagesoftenallowcollectionsofprocedurestobegroupedintomodules,therebyintroducingname-spacelocality.Theexecutionenvironmentusuallyprovidesasinglethreadofcontrolinasinglenamespace.Solution:Systemmodel:callanddefinitionhierarchy,subsystemsoftendefinedviamodularityComponents:proceduresandexplicitlyvisibledataConnectors:procedurecallsandexplicitdatasharingControlstructure:singlethread7MainProgramandSubroutine:ModelHierarchicaldecomposition:Basedondefinition-userelationshipUsesprocedurecallasinteractionmechanismSinglethreadofcontrol:SupporteddirectlybyprogramminglanguagesHierarchicalreasoning:Correctnessofasubroutinedependsonthecorrectnessofthesubroutinesitcalls。这里有递归的含义Subsystemstructureimplicit:Subroutinestypicallyaggregatedintomodules8MainProgramandSubroutine9PipesvsProceduresPipesProceduresControlAsynchronous异步,data-drivenSynchronous同步,blockingSemanticsFunctionalHierarchicalDataStreamedParameter/returnvalueVariationsBuffering,end-of-filebehaviorBindingtime,exceptionhandling,polymorphism函数式编程命令式编程10CriteriaforModularizationWhatisamodule?Commonview:apieceofcode.Buttoolimited.Compilationunit,includingrelateddeclarationsandinterfaceWhymodularizeasystem,anyway?Management:PartitiontheoveralldevelopmenteffortdivideandconquerEvolution:DecouplepartsofasystemsothatchangestoonepartareisolatedfromchangestootherpartsUnderstanding:Permitsystemtobeunderstoodascompositionofmind-sizedchunksKeyissue:whatcriteriatouseformodularization11ModuleDecompositionParnasHidesecrets.OK,what’sa“secret”?RepresentationofdataPropertiesofadevice,otherthanrequiredpropertiesTrytolocalizefuturechangeHidesystemdetailslikelytochangeindependentlyExposeininterfacesassumptionsunlikelytochangeUsefunctionstoallowforchangeThey’reeasiertochangethanvisiblerepresentation隐藏“会变”的，暴露“不变”的12Encapsulation/InformationHidingParnas:Hidesecrets(notjustrepresentations)Booch:Object’sbehaviorischaracterizedbyactionsthat

itsuffersandthatitrequiresPracticallyspeaking:Objecthasstateandoperations,butalsohasresponsibilityfortheintegrityofitsstate（state相当于内部数据成员）ObjectisknownbyitsinterfaceObjectisprobablyinstantiatedfromatemplate（类）Objecthasoperationstoaccessandalterstateandperhapsgenerator（构造函数）Therearedifferentkindsofobjects(e.g.,actor,agent,server)13Object-Oriented14DataAbstractionorObject-OrientedProblem:Thispatternissuitableforapplicationsinwhichacentralissueisidentifyingandprotectingrelatedbodiesofinformation,especiallyrepresentationinformation。OO是对现实中离散事件和个体交互的仿真，最适合模拟现实。Context:Numerousdesignmethodsprovidestrategiesforidentifyingnaturalobjects.Newerprogramminglanguagessupportvariousvariationsonthetheme,soifthelanguagechoiceorthemethodologyisfixed,thatwillstronglyinfluencetheflavorofthedecomposition.Solution:Systemmodel:localizedstatemaintenanceComponents:managers(e.g.,servers,objects,abstractdatatypes)Connectors:procedurecallControlstructure:decentralized,usuallysinglethread15ElementsofObjectArchitecturesEncapsulation:Restrictaccesstocertaininformation

封装：限制对某些信息的访问Interaction:Viaprocedurecallsorsimilarprotocol

交互：通过过程调用或类似的协议Polymorphism:Choosethemethodatrun-time

多态：在运行时选择具体的操作Inheritance:Shareddefinitionsoffunctionality

继承：对共享的功能保持唯一的接口Reuseandmaintenance:Exploitencapsulationandlocalitytoincreaseproductivity

复用和维护：利用封装和聚合提高生产力严重依赖于具体使用的语言16ProblemswithObjectApproachesManagingmanyobjectsvastseaofobjectsrequiresadditionalstructuring

大量对象需要额外的结构来容纳hierarchicaldesignsuggestedbyBoochandParnasManagingmanyinteractionssingleinterfacecanbelimiting&unwieldy(hence,“friends”)

只提供单一的接口不灵活（于是，“友元”）somelanguages/systemspermitmultipleinterfaces(innerclass,interface,multipleinheritance)DistributedresponsibilityforbehaviormakessystemhardtounderstandinteractiondiagramsnowusedindesignCapturingfamiliesofrelateddesignstypes/classesareoftennotenough类图无法表示运行时内存状态designpatterns作为解决此问题的一个分支17ManagingLargeObjectSetsPureO-OdesignleadstolargeflatsystemswithmanyobjectsSameoldproblemscanreappearHundredsofmodules=>hardtofindthingsNeedawaytoimposestructureNeedadditionalstructureanddisciplineStructuringoptionsLayers(whicharenotnecessarilyobjects)SupplementalindexHierarchicaldecomposition:bigobjectsandlittleobjects18StylisticVariationsClient-serverObjectsareprocesses

进程就是对象Asymmetric:clientknowsaboutservers,butnotviceversa

不对称：客户端知道服务器，反之则不然TieredElaborationonclient-server

C/S模式的扩展Aggregationintorun-timestrata

运行时层的结合Usuallysmallnumberoftiers

通常只有少量的层Components(later)MultipleinterfacesSpecialprotocolsfordynamicreconfiguration

支持动态配置的专门协议19Layeredsystem无处不在的层次结构硬件OS应用应用应用平台20OSI参考模型2122ThelayeredarchitecturalpatternProblem:Thispatternissuitableforapplicationsthatinvolvedistinctclassesofservicesthatcanbearrangedhierarchically.Oftentherearelayersforbasicsystem-levelservices,forutilitiesappropriatetomanyapplications,andforspecifictasksoftheapplication.Context:Frequently,eachclassofserviceisassignedtoalayerandseveraldifferentpatternsareusedtorefinethevariouslayers.Layersaremostoftenusedatthehigherlevelsofdesign,usingdifferentpatternstorefinethelayers.Solution:Systemmodel:hierarchyofopaque（不透明的）layersComponents:usuallycomposites;compositesaremostoftencollectionsofproceduresConnectors:dependsonstructureofcomponents;oftenprocedurecallsunderrestrictedvisibility,mightalsobeclient/serverControlstructure:singlethread23Thelayeredarchitecturalpattern24层次风格特点每层为上一层提供服务，使用下一层的服务，只能见到与自己邻接的层适当时候(迫不得已时)，可以允许一定的越层操作大的问题分解为若干个渐进的小问题，逐步解决，隐藏了很多复杂度修改一层，最多影响两层，而通常只能影响上层。若层之间接口稳固，则不会造成其他影响上层必须知道下层的身份，不能调整层次之间的顺序层层相调，影响性能25TheMiddlewareViewMainfeaturestieredsystemfactorout50%-90%ofapplicationindependentcodeintosharedservicesbuildonexistingtransport/communicationinfrastructureApplicationsCommonApplicationServicesCommonTransportServicesinvokes26Client/Server

服务器客户客户客户客户客户LocalLoopback27Client/ServerStyle两层C/S结构三层C/S结构B/S结构（浏览器/服务器风格）28两层Client/ServerWorkstations包含显示层与业务层，Server只有数据29两层Client/ServerC/S是基于资源不对等，且为实现共享而提出的，20世纪90年代成熟起来C/S有三个主要组成部分：数据库服务器、客户端和网络服务器（后台）负责数据管理，客户端（前台）完成与用户的交互任务。“胖客户端，瘦服务器”缺点：对客户端软硬件配置要求较高，客户端臃肿客户端程序设计复杂数据安全性不好。客户端程序可以直接访问数据库服务器。信息内容和形式单一用户界面风格不一，使用繁杂，不利用推广使用软件维护与升级困难。每个客户机上的软件都需要维护30三层Client/ServerClient-Application-Server与二层C/S结构相比，增加了一个应用服务器。整个应用逻辑驻留在应用服务器上，只有表示层存在于客户机上（“瘦客户端”）应用功能分为表示层、功能层、数据层三层表示层是应用的用户接口部分。通常使用图形用户界面功能层是应用的主体，实现具体的业务处理逻辑数据层是数据库管理系统。以上三层逻辑上独立。通常只有表示层配置在客户端中思考：“瘦客户端”的三层C/S有何优缺点？3132Client-Application-Server…33B/SB/S是三层C/S的特例客户端为http浏览器为增强功能，往往还需要安装flash、jvm及一些专用插件使用标准http/https协议要考虑浏览器兼容的问题通常只能“拉”，不能“推”客户之间的通信只能通过服务器中转安全性较难控制（SQL注入攻击等）数据查询等响应速度低于C/S体系结构服务器的负荷大，客户机的资源浪费用RIA等技术解决，主流浏览器也对硬件逐步利用到底应把主要的计算量放到客户机还是服务器？34SoftwareArchitectureStyle:

DataCentered/SharedData

3536SharedInformationSystemsStylerepresentsalargevarietyofsystems

这种风格描绘很多种系统manyvariantsdependingonnatureofshareddata

共同特点是共享数据Styleaddressesmechanismsfor:collecting,manipulatingandpreservinglargebodiesofdata

收集、操作、存储大量的数据Databasesareanaturalexample,butnottheonlyone

数据库是一个典型的例子37SharedInformationSystemsHighlevelviewwhataretheapparentfeaturesofthisstyle?whataresomeissuesregardingthisstyle?

星型结构简化了拓扑38★SharedInformationSystemsAdvantageseasytoaddconsumersandproducersofdata

很容易增加数据的生产者和消费者Howaboutmodifier?Issuessynchronization（同步）configurationandschemamanagement（配置和管理）atomicity（原子性）consistency（一致性）persistence（持久性）performance（性能）39SharedInformationSystemsLineageEarliestrepositoriesappearinbatchsequentialsystems

早期的数据共享出现在批处理系统mainframes,drums,magnetictapes,discdrivesresourcesmanuallymanagedPressureforon-lineaccesstodata

迫切需要数据即时存取requirementtomakeaccesstodataeasyandinstanthelptodrivetheshiftfrombatch-sequentialtointeractiveprocessingTodaysharedinformationsystemsappeareverywherefromthesmallestbusiness,tothemostadvancedscientificapplicationsmanyapplicationsprovideaccessmechanismstoshareddatatheWebhasbecomeagiantdistributedrepository40EvolutionofSharedInformationSystemsBatchSequentialSystemsflatfileaccess(I/O)41EvolutionofSharedInformationSystemsDatapool(SharedMemory)Example:EnabledbyavailabilityofRAMandlanguagestopermitthesharingofcommondata(E.g.,FORTRANCOMMONBLOCK)ProcessesarenotnecessarilysequentialGetsmessywithoutimplementationrules-whataretheissues?42RepositoryArchitecture除数据库外，剪贴板、注册表是典型的仓库风格的例子43EvolvingDatabaseArchitecturesBatchprocessing:Standaloneprograms（独立的程序）resultswerepassedfromonetoanotheronmag-tape（结果通过磁带从一个程序传到另一个程序）batchsequentialmodel（批处理模式）Interactiveprocessing:concurrentoperationandfasterupdatesprecludebatching,soupdatesareoutofsynchwithreports.

并行操作、更快的更新速度，但是使更新难以保持和报告同步。Repositorymodelwithexternalcontrol（仓库风格）现状：信息分散在很多数据库中问题：想买本书，如何了解哪个网站最便宜？4445UnifiedSchemasforIntegratingDatabasesAbstraction:multiplexthedatabases;put

filtersonthequery/updateto

matchdiverseviews集成多个数据库；

在查询/更新操作中

增加过滤器/包装器来匹配

不同的视图难点：查询分解、结果合并46Multi-databases47ComputerAidedSoftware

EngineeringInitiallyjusttranslationfromsourcetoobjectcode:compiler,library,linker,make

起初，就是做从源代码到目标代码的转换Grewtoincludedesignrecord,documentation,analysis,configurationcontrol,incrementality

开始包含分析、设计、调试、测试、文档、配置管理、增量编译等功能Integrationdemandedfor20years,butnothereyet.

集成已经作了20年，但还没有结束48CASEvs.DBMSAscomparedtodatabases,CASEhas:moretypesofdata

更多的数据类型fewerinstancesofeachtype

更少的数据类型实例slowerqueryrates

更慢的查询频率larger,morecomplex,lessdiscreteinformation

更大，更复杂，更集中的信息butnotshorterlifetime

生命周期没有更短49TraditionalCompiler50Example:ModernCanonicalCompiler51CanonicalCompiler52SoftwareToolswithSharedRepresentation53EvolutionofCASEEnvironmentsEvolutionismuchlikedatabases:Interaction:batch-->interactive

交互：批处理交互式Granularity:completeprocessing-->incremental

粒度：完全处理增量Coverage:compilation-->fulllifecycle

覆盖：编译全生命周期Likedatabases,startedwithbatchsequentialstyle

从批处理风格开始Integrationneedsledtorepositorieswithrigidcontrol,thentoopensystemsinlayers

对集成性的要求，促成了仓库风格被应用，让系统开始分层54RepositoryProblem:Thispatternissuitableforapplications