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1、1.Object-OrientedDesign:BridgingfromAnalysistoImplementationSystemsdesignisthebridgebetweenuserrequirementsandprogrammingthenewsystem.Onestrengthoftheobject-orientedapproachisthatthedesignmodelsareoftenjustextensionsoftherequirementsmodels.Obviously,itismucheasiertoextendanexistingmodelthantocreatee
2、ntirelynewdesignmodels.OnetenetofAgile,adaptiveapproachestodevelopmentistocreatemodelsonlyiftheyhavemeaningandarenecessary.Thedesignmodelsmaynotbeformalizedintoacomprehensivesetofdocumentsanddiagrams,buttheyarecertainlynecessary.2024/7/25第1页/共53页第一页，共54页。1.1OverviewofObject-OrientedProgramsAnobject-
3、orientedprogramconsistsofasetofprogramobjectsthatcooperatetoaccomplisharesult.Eachprogramobjecthasprogramlogicandanynecessaryattributesencapsulatedintoasingleunit.Theseobjectsworktogethebysendingeachothermessagesandworkinginconcerttosupportthefunctionsofthemainprogram.2024/7/25第2页/共53页第二页，共54页。1.1Ov
4、erviewofObject-OrientedPrograms2024/7/25第3页/共53页第三页，共54页。1.1OverviewofObject-OrientedProgramsAnobject-orientedsystemconsistsofsetsofcomputingobjects.Eachobjecthasdataandprogramlogicencapsulatedwithinitself.Thisiscalledaninstantiationoftheclassthatis,makinganinstance(anobject)basedonthetemplateprovid
5、edbytheclassdefinition.Eachobjectalsorepresentsastructureofthree-layerarchitecture.2024/7/25第4页/共53页第四页，共54页。1.2Object-OrientedDesignModelsandProcesses2024/7/25第5页/共53页第五页，共54页。1.2Object-OrientedDesignModelsandProcessesThedomainmodelclassdiagramidentifiesalltheclasses,or“things,”thatareimportantinth
6、eproblemdomain.Theusecasediagramsidentifiedtheelementarybusinessprocessesthatthesystemneedstosupportinotherwords,allthewaysuserswanttousethesystemtocarryoutprocessinggoals.Theactivitydiagramsandusecasedescriptionsdocumenttheinternalworkflowofeachusecase.2024/7/25第6页/共53页第六页，共54页。1.2Object-OrientedDe
7、signModelsandProcessesAnactivitydiagramshowsthestepsnecessarytocarryoutaparticularusecase.Thesystemsequencediagramsarecloselyrelatedtoactivitydiagrams,exceptthattheyshowthemessagesordatathataresentbackandforthbetweentheuserandthesystemduringthestepsoftheusecase.Finally,statemachinediagramskeeptracko
8、fallstatusconditionrequirementsforoneparticularclass.Theyalsoshowthebusinessrulesthatcontrolthechangingofonestate(statuscondition)toanother.2024/7/25第7页/共53页第七页，共54页。1.2Object-OrientedDesignModelsandProcessesArchitecturaldesignisoneofthefirststepsinsystemsdesign,inasmuchasitprovidesthebigpictureando
9、verallstructureofthenewsystem.Atthetopoftherightcolumnarecomponentdiagramsanddeploymentdiagrams.wenextseedesignclassdiagrams,orDCDs,whichareanexpansionofthedomainmodelclassdiagram.Thedesignversionofsequencediagramsismuchmoredetailedandisusedtocarryoutmuchofthedetaileddesignactivity.2024/7/25第8页/共53页
10、第八页，共54页。2.Object-OrientedArchitecturalDesignInmostcases,developersbegintothinkabouthowthesystemwillbedeployedandwhattheoverallstructurewilllooklikeduringtheearlystepsofrequirementsgatheringanddocumentation.Softwaresystemsaregenerallydividedintotwotypes:1.single-usersystems2.enterprise-levelsystems.
11、2024/7/25第9页/共53页第九页，共54页。2.Object-OrientedArchitecturalDesignEnterprise-levelsystemsalmostalwaysuseclient/serverarchitectureswithmultiplelayers.Characteristicofenterprise-levelsystems,thedatabaseanddataaccessareonacentralserverbecauseitisasharedresourcethroughouttheorganization.2024/7/25第10页/共53页第十
12、页，共54页。2.Object-OrientedArchitecturalDesign2024/7/25Design IssueClient/Server Network System Internet System (Web)StateStateful” or state-based system e.g., client/server connection is long term.“Stateless systeme.g., client/server connection is not long term and has no inherent memory.Client config
13、uration Screens and forms that are programmed are displayed directly.Domain layer is often on the client or split between client and servermachines.Screens and forms aredisplayed only through abrowser. They must conform to browser technologyServerconfiguration Application or data server directly con
14、nects to client tier.Client tier connectsindirectly to the application server through a Web server第11页/共53页第十一页，共54页。2.Object-OrientedArchitecturalDesignTheconceptofstaterelatestothepermanenceoftheconnectionbetweentheclientviewlayerandtheserverdomainlayer.Iftheconnectionispermanent,asinaclient/serve
15、rsystem,valuesinvariablescanbepassedbackandforthandarerememberedbyeachcomponentinthesystem.Theviewlayerhasdirectaccesstothedatafieldsinthedomainlayer.Inastatelesssystem,suchastheInternet,theclientviewlayerdoesnthaveapermanentconnectiontotheserverdomainlayer.2024/7/25第12页/共53页第十二页，共54页。2.1ComponentDi
16、agramsandArchitecturalDesignThecomponentdiagramidentifiesthelogical,reusable,andtransportable(portable?)systemcomponentsthatdefinethesystemarchitecture.Theessentialelementofacomponentdiagramisthecomponentelementwithitsinterfaces.Acomponentisanexecutablemoduleorprogram,anditconsistsofalltheclassestha
17、tarecompiledintoasingleentity.Therearetwowaystorepresentacomponent:asageneralclassorasaspecificinstance.2024/7/25第13页/共53页第十三页，共54页。2.1ComponentDiagramsandArchitecturalDesign2024/7/25第14页/共53页第十四页，共54页。StereotypingUMLdoeshaverulesforstereotypingasymbolandforextendingthelanguage2024/7/25第15页/共53页第十五页
18、，共54页。Two-LayerArchitecturalDesignofInternetSystems2024/7/25第16页/共53页第十六页，共54页。Two-LayerArchitecturalDesignofInternetSystemsThebusinesslogicinthedomainlayerfrequentlyrelatesonlytodataformattingandtodecidingwhichdatabasetabletoupdate.DuetothestructureofWebservers,theprogram(definedasobject-orientedcl
19、asses)thatprocessestheinputformsalsooutputstheHTMLcodethatissentbacktotheclientbrowser.ThebasicideaisthatevenaWeb-basedsystemcanbedevelopedinmultiplelayersoftheviewthatis,theuserinterface,themodel(whichisthebusinesslogicanddatabaseaccess),andthecontroller(whichprovidesalinkbetweentheviewandthemodel)
20、.2024/7/25第17页/共53页第十七页，共54页。2.1ComponentDiagramsandArchitecturalDesignItiscriticallyimportantforthesamebackendbusinesslogicanddatabaseaccesstolinkwitheitheruserinterface.Consequently,thedesignteammustspecifythearchitecturaldesigninenoughdetailtoensuretheprogrammersimplementasystemthatcansupportboth
21、userinterfaces.Eachcomponentisanexecutableprogramandismadeupofclasses.2024/7/25第18页/共53页第十八页，共54页。3.FundamentalPrinciplesofObject-OrientedDetailedDesignTheobjectiveofobject-orienteddetaileddesignistoidentifyandspecifyalltheobjectsthatmustworktogethertocarryouteachusecase.Onemajorresponsibilityofdeta
22、ileddesignistoidentifyanddescribeeachsetofobjectswithineachlayerandtoidentifyanddescribetheinteractionsormessagesthataresentbetweentheseobjects.Thefullsequencediagramisusedfordesignandisatypeofinteractiondiagram.Acommunicationdiagramisalsoatypeofinteractiondiagram.2024/7/25第19页/共53页第十九页，共54页。3.Funda
23、mentalPrinciplesofObject-OrientedDetailedDesign2024/7/25第20页/共53页第二十页，共54页。3.FundamentalPrinciplesofObject-OrientedDetailedDesign2024/7/25第21页/共53页第二十一页，共54页。3.FundamentalPrinciplesofObject-OrientedDetailedDesignItdescribesthesetofobject-orientedclassesneededforprogramming,navigationbetweentheclasse
24、s,attributenamesandproperties,andmethodnamesandproperties.Adesignclassdiagramisasummaryofthefinaldesignthatwasdevelopedbyusingthedetailedsequencediagrams,anditisuseddirectlywhendevelopingtheprogrammingcode.2024/7/25第22页/共53页第二十二页，共54页。Translatemodelintocode.Thesamemodelispresentedindifferentlanguage
25、s.2024/7/25第23页/共53页第二十三页，共54页。第24页/共53页第二十四页，共54页。3.1Object-OrientedDesignProcess2024/7/25第25页/共53页第二十五页，共54页。4.DesignClassesandtheDesignClassDiagramThedomainmodelclassdiagramshowsasetofproblemdomainclassesandtheirassociations.Duringanalysis,becauseitisadiscoveryprocess,analystsgenerallydontworrymu
26、chaboutthedetailsoftheattributes.However,inOOP,theattributesofaclassmust?bedeclaredas publicorprivate,andeachattributemustalsobedefinedbyitstype,suchascharacterornumeric.Duringdetaileddesign,itisimportanttoelaborateonthesedetailsaswellastodefinethemethodsandparametersthatarepassedtothemethodsandther
27、eturnvaluesfrommethods.2024/7/25第26页/共53页第二十六页，共54页。4.1DesignClassSymbolsAstereotypeissimplyawaytocategorizeamodelelementasacertaintype.Astereotypeextendsthebasicdefinitionofamodelelementbyindicatingthatithassomespecialcharacteristicwewanttohighlight.EntityControllerBoundary2024/7/25第27页/共53页第二十七页，共
28、54页。Anentityclassisthedesignidentifierforaproblemdomainclass.Itisalsousuallyapersistentclass.Apersistentclassisonewithobjectsthatexistaftertheprogramquits.Aboundaryclass,orviewclass,isspecificallydesignedtoliveonthesystemsautomationboundary.Inadesktopsystem,theseclasseswouldbethewindowsclassesandall
29、theotherclassesassociatedwiththeuserinterface.2024/7/25第28页/共53页第二十八页，共54页。4.1DesignClassSymbolsAcontrolclassmediatesbetweentheboundaryclassesandtheentityclasses.Inotherwords,itsresponsibilityistocatchthemessagesfromtheboundaryclassobjectsandsendthemtothecorrectentityclassobjects.Itactsasakindofswit
30、chboard,orcontroller,betweentheviewlayerandthedomainlayer.Adataaccessclassisusedtoretrievedatafromandsenddatatoadatabase.Ratherthaninsertdatabaseaccesslogic,includingSQLstatements,intotheentityclassmethods,aseparatelayerofclassestoaccessthedatabaseisoftenincludedinthedesign.2024/7/25第29页/共53页第二十九页，共
31、54页。4.1DesignClassSymbols2024/7/25第30页/共53页第三十页，共54页。4.1DesignClassSymbols2024/7/25第31页/共53页第三十一页，共54页。4.2DesignClassNotationTheformatthatanalystsusetodefineeachattributeincludes:VisibilityWhetherotherobjectscandirectlyaccesstheattribute.(Aplussignindicatesthatanattributeisvisible,orpublic;aminussig
32、nindicatesthatitisntvisible,orprivate.)AttributenameType-expression(suchascharacter,string,integer,number,currency,ordate)Initial-value,ifapplicableProperty(withincurlybraces),suchaskey,ifapplicable2024/7/25第32页/共53页第三十二页，共54页。4.2DesignClassNotationRememberthatintheobject-orientedapproach,aclassisat
33、emplatetocreateindividualobjectsorinstances.Thethirdcompartmentcontainsthemethodsignatureinformation.Amethodsignatureshowsalltheinformationneededtoinvoke(orcall)themethod.Itshowstheformatofthemessagethatmustbesent,whichconsistsofthese:MethodvisibilityMethodnameMethodparameterlist(incomingarguments)R
34、eturntype-expression(thetypeofthereturnparameterfromthemethod)2024/7/25第33页/共53页第三十三页，共54页。4.2DesignClassNotation2024/7/25第34页/共53页第三十四页，共54页。4.2DesignClassNotationEachofthesubclassesalsohasauniqueattributethatisunderlined,suchasnoOfPhoneSales.Underlinedattributesareclass-levelattributesandhavethesa
35、mecharacteristicsasclass-levelmethods.Aclass-levelattributeisastaticvariable,anditcontainsthesamevalueinallinstantiatedobjectsofthesametype.Anitalicizedclassnameindicatesthatitisanabstractclassaclassthatcanneverbeinstantiated.Eachofthethreesubclassesisconsideredaconcreteclassbecauseitcanbeinstantiat
36、ed;inotherwords,objectscanbecreated.2024/7/25第35页/共53页第三十五页，共54页。4.3DevelopingtheFirst-cut(初步(chb)DesignClassDiagram2024/7/25第36页/共53页第三十六页，共54页。4.3DevelopingtheFirst-CutDesignClassDiagramThefirst-cutdesignclassdiagramisdevelopedbyextendingthedomainmodelclassdiagram.Itrequirestwosteps:(1)elaborating
37、ontheattributeswithtypeandinitialvalueinformationand(2)addingnavigationvisibilityarrows.Asindicatedearlier,object-orienteddesignisusecasedriven.2024/7/25第37页/共53页第三十七页，共54页。4.3DevelopingtheFirst-CutDesignClassDiagram2024/7/25第38页/共53页第三十八页，共54页。AttributeVisibility,NavigationandNavigationVisibilityHe
38、reareafewgeneralguidelines:One-to-manyassociationsthatindicateasuperior/subordinaterelationshipareusuallynavigatedfromthesuperiortothesubordinateforexample,fromSaletoSaleItem.Sometimes,theserelationshipsformhierarchiesofnavigationchainsforexample,fromPromotiontoProductItemtoInventoryItem.Mandatoryas
39、sociations,inwhichobjectsinoneclasscantexistwithoutobjectsofanotherclass,areusuallynavigatedfromthemoreindependentclasstothedependentclassforexample,fromCustomertoSale.Whenanobjectneedsinformationfromanotherobject,anavigationarrowmightberequired,pointingeithertotheobjectitselfortoitsparentinahierarc
40、hy.Navigationarrowsmaybebidirectional.2024/7/25第39页/共53页第三十九页，共54页。4.3DevelopingtheFirst-CutDesignClassDiagram2024/7/25第40页/共53页第四十页，共54页。4.3DevelopingtheFirst-CutDesignClassDiagramThreepointsareimportanttonote.1.First,asdetaileddesignproceedsusecasebyusecase,weneedtoensurethatthesequencediagramssup
41、portandimplementthenavigationthatwasinitiallydefined.2.Second,thenavigationarrowsneedtobeupdatedasdesignprogressestobeconsistentwiththedesigndetails.3.Finally,methodsignatureswillbeaddedtoeachclassbasedonthedesigndecisionsmadewhencreatingthesequencediagramsfortheusecases.2024/7/25第41页/共53页第四十一页，共54页
42、。5.DetailedDesignwithCRCCardsCRCcardsareabrainstormingtechniquethatisquitepopularamongobjectorienteddevelopers.Here,“CRC”isanacronymforClassResponsibilityCollaboration.2024/7/25第42页/共53页第四十二页，共54页。5.DetailedDesignwithCRCCardsForeachusecaseyouneedtodesign,thesestepsaredoneiteratively:1.Selectingausec
43、ase2.IdentifyingtheproblemdomainclassthathasresponsibilityforthisusecaseThisobjectwillreceivethefirstmessagefromtheusecasecontroller.Usingthedomainmodelthatwasdevelopedduringanalysis,selectoneclasstotakeresponsibility.Focusonlyontheproblemdomainclasses.Ontheleftsideofthecard,writetheobjectsresponsib
44、ility.3.Identifyingotherclassesthatmustcollaboratewiththeprimaryobjectclasstocompletetheusecase2024/7/25第43页/共53页第四十三页，共54页。5.DetailedDesignwithCRCCardsAttheendofthisprocess,youwillhaveasmallsetofCRCcardsthatcollaboratetosupporttheusecase.Anotherhelpfulstepistoincludetheuser-interfaceclasses.Anyothe
45、rrequiredutilityclassescanalsobeaddedtothesolution.2024/7/25第44页/共53页第四十四页，共54页。5.DetailedDesignwithCRCCards2024/7/25第45页/共53页第四十五页，共54页。6.FundamentalDetailedDesignPrinciplesCouplingCouplingisaqualitativemeasureofhowcloselytheclassesinadesignclassdiagramarelinked.Asimplewaytothinkaboutcouplingisasth
46、enumberofnavigationarrowsonthedesignclassdiagram.Lowcouplingisusuallybetterforasystemthanhighcoupling.Inotherwords,fewernavigationvisibilityarrowsindicatethatasystemiseasiertounderstandandmaintain.2024/7/25第46页/共53页第四十六页，共54页。6.FundamentalDetailedDesignPrinciplesCohesionButwhatifthatsameobjectalsoha
47、dmethodstomakeclassroomassignmentsorassignprofessorstocourses?Thecohesivenessoftheclasswouldbereduced.Classeswithlowcohesionhaveseveralnegativeeffects.First,theyarehardtomaintain.Second,itishardtoreusesuchclasses.2024/7/25第47页/共53页第四十七页，共54页。6.FundamentalDetailedDesignPrinciplesProtectionfromvariati
48、onsOneoftheunderlyingprinciplesofgooddesignisprotectionfromvariationstheideathatthepartsofasystemthatareunlikelytochangeshouldbesegregated(orprotected)fromthosethatwillchange.Protectionfromvariationsisaprinciplethatdrivesthemultilayerdesignpattern.2024/7/25第48页/共53页第四十八页，共54页。6.FundamentalDetailedDe
49、signPrinciplesIndirectionIndirectionistheprincipleofdecouplingtwoclassesorothersystemcomponentsbyplacinganintermediateclassbetweenthemtoserveasalink.Inotherwords,instructionsdontgodirectlyfromAtoB;theyaresentthroughCfirst.Orinmessageterminology,dontsendamessagefromAtoB;letAsendthemessagetoCandthenle
50、tCforwardittoB.Insertinganintermediateobjectallowsanyvariationsinonesystemtobeisolatedinthatintermediateobject.Indirectionisalsousefulformanycorporatesecuritysystems.2024/7/25第49页/共53页第四十九页，共54页。ObjectResponsibilityOneofthemostfundamentalprinciplesofobject-orienteddevelopmentistheideaofobjectrespons
51、ibility;thatis,objectsareresponsibleforcarryingoutthesystemprocessing.Theseresponsibilitiesarecategorizedintwomajorareas:1.KnowingWhatisanobjectexpectedtoknow?2.Doing.Whatisanobjectexpectedtodoortoinitiate?2024/7/25第50页/共53页第五十页，共54页。ObjectResponsibility:Knowning“Knowing”includesanobjectsresponsibil
52、itiesforknowingaboutitsowndataandknowingaboutotherclasseswithwhichitmustcollaboratetocarryoutusecases.Obviously,aclassshouldknowaboutitsowndata,whatattributesexist,andhowtomaintaintheinformationinthoseattributes.Anobjectshouldknowaboutorhavenavigationvisibilitytootherobjectsthatcanprovidetherequired
53、information.2024/7/25第51页/共53页第五十一页，共54页。ObjectResponsibility:Doing“Doing”includesalltheactivitiesanobjectdoestoassistinexecutingausecase.Someofthoseactivitiesincludereceivingandprocessingmessages.Anotheractivityistoinstantiate,orcreate,newobjectsthatmayberequiredforcompletionofausecase.Classesmustc
54、ollaboratetocarryoutausecase,andsomeclassesareresponsibleforcoordinatingthecollaboration.2024/7/25第52页/共53页第五十二页，共54页。2024/7/25感谢您的欣赏(xnshng)！第53页/共53页第五十三页，共54页。内容(nirng)总结1. Object-Oriented Design: Bridging from Analysis to Implementation。“Stateless systeme.g.,。Initial-value, if applicable。感谢您的欣赏(xnshng)第五十四页，共54页。
