软件工程-实践者的研究方法 (3)

1Chapter3AgileDevelopmentSoftwareEngineering:APractitioner’sApproach,7/ebyRogerS.PressmanFornon-profiteducationaluseonlyMaybereproducedONLYforstudentuseattheuniversitylevelwhenusedinconjunctionwithSoftwareEngineering:APractitioner'sApproach,7/e.Anyotherreproductionoruseisprohibitedwithouttheexpresswrittenpermissionoftheauthor.2TheManifesto(宣言)forAgileSoftwareDevelopment“Weareuncoveringbetterwaysofdevelopingsoftwarebydoingitandhelpingothersdoit.Throughthisworkwehavecometovalue:•Individualsandinteractionsoverprocessesandtools•Workingsoftwareovercomprehensivedocumentation•Customercollaborationovercontractnegotiation•RespondingtochangeoverfollowingaplanThatis,whilethereisvalueintheitemsontheright,wevaluetheitemsontheleftmore.”KentBecketal3Whatis“Agility”?Effective(rapidandadaptive)responsetochangeEffectivecommunicationamongallstakeholdersOrganizingateamsothatitisincontroloftheworkperformedYielding…Rapid,incrementaldeliveryofsoftware传统软件开发方法：强调过程；强调文档；开发人员负担过重软件开发的新挑战：快速进入市场要求高生产率；快速变化的需求；快速发展的技术4AgilityandtheCostofChange5AnAgileProcessIsdrivenbycustomerdescriptionsofwhatisrequired(scenarios)Recognizesthatplansareshort-livedDevelopssoftwareiterativelywithaheavyemphasisonconstructionactivitiesDeliversmultiple‘softwareincrements’Adaptsaschangesoccur6AgilityPrinciples-I1.Ourhighestpriorityistosatisfythecustomerthroughearlyandcontinuousdeliveryofvaluablesoftware.2.Welcomechangingrequirements,evenlateindevelopment.Agileprocessesharnesschangeforthecustomer'scompetitiveadvantage.3.Deliverworkingsoftwarefrequently,fromacoupleofweekstoacoupleofmonths,withapreferencetotheshortertimescale.4.Businesspeopleanddevelopersmustworktogetherdailythroughouttheproject.5.Buildprojectsaroundmotivatedindividuals.Givethemtheenvironmentandsupporttheyneed,andtrustthemtogetthejobdone.6.Themostefficientandeffectivemethodofconveyinginformationtoandwithinadevelopmentteamisface–to–faceconversation.7AgilityPrinciples-II7.Workingsoftwareistheprimarymeasureofprogress.(可运行的软件是测量项目进展的主要依据)8.Agileprocessespromotesustainabledevelopment(敏捷过程提倡可持续的开发).Thesponsors,developers,andusersshouldbeabletomaintainaconstantpaceindefinitely.9.Continuousattentiontotechnicalexcellenceandgooddesignenhancesagility.10.Simplicity–theartofmaximizingtheamountofworknotdone–isessential.11.Thebestarchitectures,requirements,anddesignsemergefromself–organizingteams.12.Atregularintervals,theteamreflectson(反思)howtobecomemoreeffective,thentunesandadjustsitsbehavioraccordingly.8HumanFactorstheprocessmoldstotheneedsofthepeopleandteam,nottheotherwayaroundkeytraits(特征)mustexistamongthepeopleonanagileteamandtheteamitself:Competence(技能).Commonfocus.Collaboration.Decision-makingability.Fuzzyproblem-solvingability.Mutualtrustandrespect.Self-organization.9ExtremeProgramming(XP)Themostwidelyusedagileprocess,originallyproposedbyKentBeckXPPlanningBeginswiththecreationof“userstories”AgileteamassesseseachstoryandassignsacostStoriesaregroupedtoforadeliverableincrementAcommitment(承诺)ismadeondeliverydateAfterthefirstincrement“projectvelocity”isusedtohelpdefinesubsequentdeliverydatesforotherincrements10Userstories类似于usecases替代详细的用户需求规格说明书由用户书写，但不局限于界面的描述没有技术术语，能够成为验收测试的依据例如：描述买饮料过程的Userstory1.用户投入一些钱。2.售货机显示用户已经投了多少钱。3.如果投入的钱足够买某种饮料，这种饮料对应的按钮的灯就会亮。4.用户按了某个亮了的按钮。5.售货机卖出一罐饮料给他。6.售货机找零钱给他。11DeliverableincrementReleaseplanning计划向客户发布多个版本通过召开专门的会议releaseplanningmeeting来制订一份发布计划(发布计划详细描述用户各版本的要求)。对用户业务有重要影响的功能可在早期加入到系统中。越晚向用户介绍系统的总体特征，开发队伍所获得的完成时间越短。12ExtremeProgramming(XP)XPDesignFollowstheKISprinciple(keepitsimple)EncouragetheuseofCRCcards(Class-Responsibility-Collaboration)Fordifficultdesignproblems,suggeststhecreationof“spike(探针)solutions”—adesignprototypeEncourages“refactoring(重构)”—aniterativerefinementoftheinternalprogramdesign13SimplicityistheKey决不增加没有列入到进度中的功能设计只考虑当前定义的功能而不考虑以后需求的变化；该设计是完成目前功能所需的最简洁的设计。14CRCCardsClass,Responsibilities,andCollaboration(CRC)每个CRC卡片表示一个对象类，表明类名、责任和每个责任需要交互的其他类。CRC卡帮助Team交流设计思想，简化设计文档15Spikesolutions探针方案对不确定的需求和设计等，通过写一些可执行原型程序、进行详细设计或者演算等等方式做探测和尝试，以降低潜在的风险。这些探测过程称为SPIKE。16Refactor(重构)在不影响程序的外部行为的情况下，按“高内聚、低耦合”的原则对程序结构进行改进，优化设计结构，保持代码简洁、无冗余。17ExtremeProgramming(XP)XPCodingRecommendstheconstructionofaunittestforastorebeforecodingcommencesEncourages“pairprogramming”On-siteCustomerXPTestingAllunittestsareexecuteddaily“Acceptancetests”aredefinedbythecustomerandexcutedtoassesscustomervisiblefunctionality18PairProgramming所有发布的代码都由两个程序员在一台机器上共同开发。结对编程的最好方式是两人共同坐在显示器前，将键盘和鼠标在两人之间“滑动”，一人考虑所创建的方法，而另一人同时考虑该方法如何在类中得到更好的体现。19On-siteCustomer客户是Team成员，在开发现场和开发人员一起工作。传统的客户任务一般是提出需求，承担验收测试，接收发布的系统。XP新增加的任务：(1)写UserStory；(2)评估UserStory的商业优先级；(3)为每个UserStory定义验收测试；(4)计划开发内容；(5)调控开发过程。20ExtremeProgramming(XP)unittestcontinuousintegrationacceptancetestingpairprogrammingReleaseuserstoriesvaluesacceptancetestcriteriaiterationplansimpledesignCRCcardsspikesolutionsprototypesrefactoringsoftwareincrementprojectvelocitycomputed21Iteration根据交付计划和项目速率，选择要优先完成的userstory，将其分解为1～n天内完成的任务，制订本次迭代计划，然后通过每天的站立会议解决碰到的问题，调整迭代计划，会后是代码共享式的开发工作。开发人