SA02.2 Style 調(diào)用返回 倉庫

1SE3121021:SoftwareArchitecture

SoftwareArchitectureStyle

2SoftwareArchitectureStyle:Call/Return

調(diào)用/返回

3Call/Return的不同種類Mainprogramandsubroutines主程序和子程序Classicalprogrammingparadigm-functionaldecompositionObject-Oriented/AbstractDataTypesInformation(representation,accessmethod)hidingLayeredhierarchiesEachlevelonlycommunicateswithitsimmediateneighborsOtherClient/Server……4HistoryMainprogramandsubroutines單線程控制，劃分為若干處理步驟Functionalmodules把處理步驟集成到模塊內(nèi)AbstractDataTypes操作和數(shù)據(jù)捆綁在一起，隱藏具體實(shí)現(xiàn)Objects方法（動態(tài)綁定），多態(tài)（子類），重用（繼承）OOArchitectures對象活動在不同的進(jìn)程/線程Client/Server,tieredstylesComponents多個接口，二進(jìn)制兼容，中間件也是編程語言的發(fā)展歷程5MainProgramandSubroutine思考：此圖為有向圖，是否可能出現(xiàn)環(huán)？6MainProgramandSubroutineProblem:Thispatternissuitableforapplicationsinwhichthecomputationcanappropriatelybedefinedviaahierarchyofproceduredefinitions.存在層次結(jié)構(gòu)Context:Manyprogramminglanguagesprovidenaturalsupportfordefiningnestedcollectionsofprocedures（過程的嵌套）andforcallingthemhierarchically.Theselanguagesoftenallowcollectionsofprocedurestobegroupedintomodules,therebyintroducingname-spacelocality.Theexecutionenvironmentusuallyprovidesasinglethreadofcontrolinasinglenamespace.Solution:Systemmodel:callanddefinitionhierarchy,subsystemsoftendefinedviamodularityComponents:proceduresandexplicitlyvisibledataConnectors:procedurecallsandexplicitdatasharingControlstructure:singlethread7MainProgramandSubroutine:ModelHierarchicaldecomposition:Basedondefinition-userelationshipUsesprocedurecallasinteractionmechanismSinglethreadofcontrol:SupporteddirectlybyprogramminglanguagesHierarchicalreasoning:Correctnessofasubroutinedependsonthecorrectnessofthesubroutinesitcalls。這里有遞歸的含義Subsystemstructureimplicit:Subroutinestypicallyaggregatedintomodules8MainProgramandSubroutine9PipesvsProceduresPipesProceduresControlAsynchronous異步,data-drivenSynchronous同步,blockingSemanticsFunctionalHierarchicalDataStreamedParameter/returnvalueVariationsBuffering,end-of-filebehaviorBindingtime,exceptionhandling,polymorphism函數(shù)式編程命令式編程10CriteriaforModularizationWhatisamodule?Commonview:apieceofcode.Buttoolimited.Compilationunit,includingrelateddeclarationsandinterfaceWhymodularizeasystem,anyway?Management:PartitiontheoveralldevelopmenteffortdivideandconquerEvolution:DecouplepartsofasystemsothatchangestoonepartareisolatedfromchangestootherpartsUnderstanding:Permitsystemtobeunderstoodascompositionofmind-sizedchunksKeyissue:whatcriteriatouseformodularization11ModuleDecompositionParnasHidesecrets.OK,what’sa“secret”?RepresentationofdataPropertiesofadevice,otherthanrequiredpropertiesTrytolocalizefuturechangeHidesystemdetailslikelytochangeindependentlyExposeininterfacesassumptionsunlikelytochangeUsefunctionstoallowforchangeThey’reeasiertochangethanvisiblerepresentation隱藏“會變”的，暴露“不變”的12Encapsulation/InformationHidingParnas:Hidesecrets(notjustrepresentations)Booch:Object’sbehaviorischaracterizedbyactionsthat

itsuffersandthatitrequiresPracticallyspeaking:Objecthasstateandoperations,butalsohasresponsibilityfortheintegrityofitsstate（state相當(dāng)于內(nèi)部數(shù)據(jù)成員）ObjectisknownbyitsinterfaceObjectisprobablyinstantiatedfromatemplate（類）Objecthasoperationstoaccessandalterstateandperhapsgenerator（構(gòu)造函數(shù)）Therearedifferentkindsofobjects(e.g.,actor,agent,server)13Object-Oriented14DataAbstractionorObject-OrientedProblem:Thispatternissuitableforapplicationsinwhichacentralissueisidentifyingandprotectingrelatedbodiesofinformation,especiallyrepresentationinformation。OO是對現(xiàn)實(shí)中離散事件和個體交互的仿真，最適合模擬現(xiàn)實(shí)。Context:Numerousdesignmethodsprovidestrategiesforidentifyingnaturalobjects.Newerprogramminglanguagessupportvariousvariationsonthetheme,soifthelanguagechoiceorthemethodologyisfixed,thatwillstronglyinfluencetheflavorofthedecomposition.Solution:Systemmodel:localizedstatemaintenanceComponents:managers(e.g.,servers,objects,abstractdatatypes)Connectors:procedurecallControlstructure:decentralized,usuallysinglethread15ElementsofObjectArchitecturesEncapsulation:Restrictaccesstocertaininformation

封裝：限制對某些信息的訪問Interaction:Viaprocedurecallsorsimilarprotocol

交互：通過過程調(diào)用或類似的協(xié)議Polymorphism:Choosethemethodatrun-time

多態(tài)：在運(yùn)行時選擇具體的操作Inheritance:Shareddefinitionsoffunctionality

繼承：對共享的功能保持唯一的接口Reuseandmaintenance:Exploitencapsulationandlocalitytoincreaseproductivity

復(fù)用和維護(hù)：利用封裝和聚合提高生產(chǎn)力嚴(yán)重依賴于具體使用的語言16ProblemswithObjectApproachesManagingmanyobjectsvastseaofobjectsrequiresadditionalstructuring

大量對象需要額外的結(jié)構(gòu)來容納hierarchicaldesignsuggestedbyBoochandParnasManagingmanyinteractionssingleinterfacecanbelimiting&unwieldy(hence,“friends”)

只提供單一的接口不靈活（于是，“友元”）somelanguages/systemspermitmultipleinterfaces(innerclass,interface,multipleinheritance)DistributedresponsibilityforbehaviormakessystemhardtounderstandinteractiondiagramsnowusedindesignCapturingfamiliesofrelateddesignstypes/classesareoftennotenough類圖無法表示運(yùn)行時內(nèi)存狀態(tài)designpatterns作為解決此問題的一個分支17ManagingLargeObjectSetsPureO-OdesignleadstolargeflatsystemswithmanyobjectsSameoldproblemscanreappearHundredsofmodules=>hardtofindthingsNeedawaytoimposestructureNeedadditionalstructureanddisciplineStructuringoptionsLayers(whicharenotnecessarilyobjects)SupplementalindexHierarchicaldecomposition:bigobjectsandlittleobjects18StylisticVariationsClient-serverObjectsareprocesses

進(jìn)程就是對象Asymmetric:clientknowsaboutservers,butnotviceversa

不對稱：客戶端知道服務(wù)器，反之則不然TieredElaborationonclient-server

C/S模式的擴(kuò)展Aggregationintorun-timestrata

運(yùn)行時層的結(jié)合Usuallysmallnumberoftiers

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

支持動態(tài)配置的專門協(xié)議19Layeredsystem無處不在的層次結(jié)構(gòu)硬件OS應(yīng)用應(yīng)用應(yīng)用平臺20OSI參考模型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層次風(fēng)格特點(diǎn)每層為上一層提供服務(wù)，使用下一層的服務(wù)，只能見到與自己鄰接的層適當(dāng)時候(迫不得已時)，可以允許一定的越層操作大的問題分解為若干個漸進(jìn)的小問題，逐步解決，隱藏了很多復(fù)雜度修改一層，最多影響兩層，而通常只能影響上層。若層之間接口穩(wěn)固，則不會造成其他影響上層必須知道下層的身份，不能調(diào)整層次之間的順序?qū)訉酉嗾{(diào)，影響性能25TheMiddlewareViewMainfeaturestieredsystemfactorout50%-90%ofapplicationindependentcodeintosharedservicesbuildonexistingtransport/communicationinfrastructureApplicationsCommonApplicationServicesCommonTransportServicesinvokes26Client/Server

服務(wù)器客戶客戶客戶客戶客戶LocalLoopback27Client/ServerStyle兩層C/S結(jié)構(gòu)三層C/S結(jié)構(gòu)B/S結(jié)構(gòu)（瀏覽器/服務(wù)器風(fēng)格）28兩層Client/ServerWorkstations包含顯示層與業(yè)務(wù)層，Server只有數(shù)據(jù)29兩層Client/ServerC/S是基于資源不對等，且為實(shí)現(xiàn)共享而提出的，20世紀(jì)90年代成熟起來C/S有三個主要組成部分：數(shù)據(jù)庫服務(wù)器、客戶端和網(wǎng)絡(luò)服務(wù)器（后臺）負(fù)責(zé)數(shù)據(jù)管理，客戶端（前臺）完成與用戶的交互任務(wù)?！芭挚蛻舳?，瘦服務(wù)器”缺點(diǎn)：對客戶端軟硬件配置要求較高，客戶端臃腫客戶端程序設(shè)計復(fù)雜數(shù)據(jù)安全性不好?？蛻舳顺绦蚩梢灾苯釉L問數(shù)據(jù)庫服務(wù)器。信息內(nèi)容和形式單一用戶界面風(fēng)格不一，使用繁雜，不利用推廣使用軟件維護(hù)與升級困難。每個客戶機(jī)上的軟件都需要維護(hù)30三層Client/ServerClient-Application-Server與二層C/S結(jié)構(gòu)相比，增加了一個應(yīng)用服務(wù)器。整個應(yīng)用邏輯駐留在應(yīng)用服務(wù)器上，只有表示層存在于客戶機(jī)上（“瘦客戶端”）應(yīng)用功能分為表示層、功能層、數(shù)據(jù)層三層表示層是應(yīng)用的用戶接口部分。通常使用圖形用戶界面功能層是應(yīng)用的主體，實(shí)現(xiàn)具體的業(yè)務(wù)處理邏輯數(shù)據(jù)層是數(shù)據(jù)庫管理系統(tǒng)。以上三層邏輯上獨(dú)立。通常只有表示層配置在客戶端中思考：“瘦客戶端”的三層C/S有何優(yōu)缺點(diǎn)？3132Client-Application-Server…33B/SB/S是三層C/S的特例客戶端為http瀏覽器為增強(qiáng)功能，往往還需要安裝flash、jvm及一些專用插件使用標(biāo)準(zhǔn)http/https協(xié)議要考慮瀏覽器兼容的問題通常只能“拉”，不能“推”客戶之間的通信只能通過服務(wù)器中轉(zhuǎn)安全性較難控制（SQL注入攻擊等）數(shù)據(jù)查詢等響應(yīng)速度低于C/S體系結(jié)構(gòu)服務(wù)器的負(fù)荷大，客戶機(jī)的資源浪費(fèi)用RIA等技術(shù)解決，主流瀏覽器也對硬件逐步利用到底應(yīng)把主要的計算量放到客戶機(jī)還是服務(wù)器？34SoftwareArchitectureStyle:

DataCentered/SharedData

3536SharedInformationSystemsStylerepresentsalargevarietyofsystems

這種風(fēng)格描繪很多種系統(tǒng)manyvariantsdependingonnatureofshareddata

共同特點(diǎn)是共享數(shù)據(jù)Styleaddressesmechanismsfor:collecting,manipulatingandpreservinglargebodiesofdata

收集、操作、存儲大量的數(shù)據(jù)Databasesareanaturalexample,butnottheonlyone

數(shù)據(jù)庫是一個典型的例子37SharedInformationSystemsHighlevelviewwhataretheapparentfeaturesofthisstyle?whataresomeissuesregardingthisstyle?

星型結(jié)構(gòu)簡化了拓?fù)?8★SharedInformationSystemsAdvantageseasytoaddconsumersandproducersofdata

很容易增加數(shù)據(jù)的生產(chǎn)者和消費(fèi)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

早期的數(shù)據(jù)共享出現(xiàn)在批處理系統(tǒng)mainframes,drums,magnetictapes,discdrivesresourcesmanuallymanagedPressureforon-lineaccesstodata

迫切需要數(shù)據(jù)即時存取requirementtomakeaccesstodataeasyandinstanthelptodrivetheshiftfrombatch-sequentialtointeractiveprocessingTodaysharedinformationsystemsappeareverywherefromthesmallestbusiness,tothemostadvancedscientificapplicationsmanyapplicationsprovideaccessmechanismstoshareddatatheWebhasbecomeagiantdistributedrepository40EvolutionofSharedInformationSystemsBatchSequentialSystemsflatfileaccess(I/O)41EvolutionofSharedInformationSystemsDatapool(SharedMemory)Example:EnabledbyavailabilityofRAMandlanguagestopermitthesharingofcommondata(E.g.,FORTRANCOMMONBLOCK)ProcessesarenotnecessarilysequentialGetsmessywithoutimplementationrules-whataretheissues?42RepositoryArchitecture除數(shù)據(jù)庫外，剪貼板、注冊表是典型的倉庫風(fēng)格的例子43EvolvingDatabaseArchitecturesBatchprocessing:Standaloneprograms（獨(dú)立的程序）resultswerepassedfromonetoanotheronmag-tape（結(jié)果通過磁帶從一個程序傳到另一個程序）batchsequentialmodel（批處理模式）Interactiveprocessing:concurrentoperationandfasterupdatesprecludebatching,soupdatesareoutofsynchwithreports.

并行操作、更快的更新速度，但是使更新難以保持和報告同步。Repositorymodelwithexternalcontrol（倉庫風(fēng)格）現(xiàn)狀：信息分散在很多數(shù)據(jù)庫中問題：想買本書，如何了解哪個網(wǎng)站最便宜？4445UnifiedSchemasforIntegratingDatabasesAbstraction:multiplexthedatabases;put

filtersonthequery/updateto

matchdiverseviews集成多個數(shù)據(jù)庫；

在查詢/更新操作中

增加過濾器/包裝器來匹配

不同的視圖難點(diǎn)：查詢分解、結(jié)果合并46Multi-databases47ComputerAidedSoftware

EngineeringInitiallyjusttranslationfromsourcetoobjectcode:compiler,library,linker,make

起初，就是做從源代碼到目標(biāo)代碼的轉(zhuǎn)換Grewtoincludedesignrecord,documentation,analysis,configurationcontrol,incrementality

開始包含分析、設(shè)計、調(diào)試、測試、文檔、配置管理、增量編譯等功能Integrationdemandedfor20years,butnothereyet.

集成已經(jīng)作了20年，但還沒有結(jié)束48CASEvs.DBMSAscomparedtodatabases,CASEhas:moretypesofdata

更多的數(shù)據(jù)類型fewerinstancesofeachtype

更少的數(shù)據(jù)類型實(shí)例slowerqueryrates

更慢的查詢頻率larger,morecomplex,lessdiscreteinformation

更大，更復(fù)雜，更集中的信息butnotshorterlifetime

生命周期沒有更短49TraditionalCompiler50Example:ModernCanonicalCompiler51CanonicalCompiler52SoftwareToolswithSharedRepresentation53EvolutionofCASEEnvironmentsEvolutionismuchlikedatabases:Interaction:batch-->interactive

交互：批處理交互式Granularity:completeprocessing-->incremental

粒度：完全處理增量Coverage:compilation-->fulllifecycle

覆蓋：編譯全生命周期Likedatabases,startedwithbatchsequentialstyle

從批處理風(fēng)格開始Integrationneedsledtorepositorieswithrigidcontrol,thentoopensystemsinlayers

對集成性的要求，促成了倉庫風(fēng)格被應(yīng)用，讓系統(tǒng)開始分層54RepositoryProblem:Thispatternissuitableforapplications