外文翻译使用开放源码工具的专业便携式开发文档格式.docx

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DesignPatternConsiderationsinYourPortalClearly,therearemanywaystoimplementadesignthatcannotbeexpressedadequatelyinthischapteralone.Hopefully,theintroductionofhigh-levelpatternconstructsandbriefdiscussionoftheimplementationofJavastandardsinthischaptercanfacilitateyourdesigndecisionsonyourportaldeployments.

Javalanguageandimplementationstandardscanalsohelpcontrolcomplexitysothatconsistentlevelsofqualitycanbeattainedinyourdevelopmentactivities.Thisinturncanleadtoincreasedpartneradoptionandportletmaintenance.Last,theadoptionofdesignpatternsshouldbeappliedsothatbestpracticesarepropagatedinyourportaldeploymentanddevelopmentoperationscanbehastened.

MuchhasbeenwrittenduringthelastfewyearsaboutdesignpatternsandtheiruseinJavadevelopment,soratherthangointogreatelaborationoftheiruse,wefeltthatitwouldbemorebeneficialtoprovidehigh-levelconceptsofpatternsthatmightbeusedinyourportaldeploymentsandtoencourageyoutoexplorethemfromtheonlineJavaworldnewsletterandfromtheCoreJ2EEPatternsbook[ALUR].

PlanningforPortalDeployment

UsingJavaStandards

Formanymission-criticaldevelopmentportalefforts,decisionsneedtobemadeaboutexpensivesoftwareprocurementstosatisfyyourdevelopmentneeds.Inordertoprotectthisinvestment,itiswisetoconsiderstandardswhenyoumakeyourpurchasingdecisionbecausethereisnothingworsethandumpingalotofmoneyintoaparticularframeworkonlytolearnafteryouhaveobtaineditthatitisaclosed,proprietarysystemthatdoesnotworkwellwithothersystems.Toguaranteethatthisdoesnothappentoyou,youshouldbecomefamiliarwithsoftwarestandardsandotherapplicationframeworks’useofthem.Regrettably,systemsthatdorelyheavilyonproprietaryextensionsoftenforceyourprojecttohireexpensiveexpertisetohelpyoudeployyourprogramwiththeirframework.

Figure7.21illustratessomeoftheJavastandardsthatcouldbeconsideredforportaldevelopment.Itisimportanttorememberthattheseneedtobeestablishedpriortoprocuringaportalframeworkorintegratingexistingapplicationsintoahomegrownportalapplication.AlwaysbecognizantofthelatestversionsofthestandardslistedinFigure7.21,andtheeffectsthatnewerversionsofthosestandardsmighthaveonyourdesigndecisions.

Figure7.21

Figure7.22illustratessomeoftheportalstandardsthatshouldbeconsideredbeforebuildingyourportalapplication.

Onmanyportalimplementations,abusinesscaseforadherencetolanguagestandardsthatrelatetoindividualportletsneedstobemadesothatproprietaryextensionsarenotadoptedbyaprogramthatdisallowscodereuseandpromotesvendorlock-in.Beingexposedtoproprietarydataformats,oneinevitablygetsincreasinglylockedintothesolutionsofaparticularvendor,whichinturnlimitstheoptionsforapplicationsoftware.Thisultimatelyenablesvendorstodictateenhancementpricesandintroducesunnecessaryriskstoyoursystem

Figure7.22

Model-View-Controller（MVC）Pattern

IntheportalarchitectureshowninFigure7.23,theMVCPatterniswheretheservletcontrollerrendersdifferentviewstotheportalfaç

adefromadisparatesetofdatasources.

Themodelisthepiecethathasnospecificknowledgeofitscontrollersoritsviews.Theportalsystemmaintainsrelationsbetweenthedifferentmodelsandviewsandbroadcastscontenttotheviewswhenthemodelchangesstate.Theviewistypicallythepiecethatmanagesthevisualizationsofthemodeldata.Thecontrolleristhepiecethatmanagesuserinteractionwiththemodeldata.

TheMVCPatternisusedwithmanyframeworksbecauseofitsabilitytohandlecontentdeliverycomplexitiesthatareprominentinmanyenterprisesystems.Jakarta’sStrutsandBEA’sWebFlowaretwonotableimplementationsthatusethisintheirframeworks.

TemplateMethodPattern

AgoodpracticewhendevelopingJavaBeansinyourportalapplicationsistousetheTemplateMethodPattern[GoF]toenforceacommondesignacrosstheportalback-end.TheTemplateMethodPatterncanbeusedsothatmodificationstoyourgetand/orsetmethodswillnotaffectyourpresentationview.

IntheportaldisplayinFigure7.23,theJavaBeanapplicationsontheback-endimplementtheTemplateMethodPatterntomanagethelogicintheaccessor（get/set）methods.

MementoPattern

InthesampleportalvisualizationshowninFigure7.23,theviewlabeled#4indicatesthataformwillberenderedtotheuserdisplay.Inmanycases,theformwilluseJavaScripttoperformvalidationtestingsothatactivitieswillbeperformedontheclientsideinordertoalleviateunnecessaryoperationsontheserver.ThisisagoodpracticeforsomeWebappl