14_j2ee_web_component_introductionnew

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1、J2EEWebComponentIntroductionUnit14UnitobjectivesAftercompletingthisunit,youshouldbeableto:UnderstandthestagesinthedevelopmentofWebapplicationsDescribethemodel-view-controller(MVC)designpatternUnderstandtheimportanceofMVCinJ2EEapplicationsDescribethewebcomponentsan

2、dcontainersprovidedbyaJ2EEplatformDescribethewebarchitectureofJ2EE2WebApplicationEvolution–StaticClientNetworkServerHTTPRequestWebBrowserWebServerHTTPResponseFileSystemOrganizationswanttomaketheirinformationavailabletoasmanypeopleintheworldaspossibleThiscanbeachiev

3、edbyusingtheWeb,deliveringtheinformationasstaticHTMLpages3WebApplicationEvolution–AppletsClientNetworkServerWebBrowserHTTPRequestwithJVMWebServerHTTPResponseFileSystemWithstaticHTML,usersseepassivepagepresentationswhicharealwaysthesamePresentationcanbeimprovedwithJa

4、vaappletsorotherclient-sideprograms4WebApplicationEvolution–ServletsClientHTTPRequestServerNetworkWebBrowserWebServerPlug-inRequestsforRequestsforstaticdynamicresourcesresourcesHTTPResponseDynamicWebServerresponseWebContainerFileSystemAppletscannotaccessdataonback-en

5、dsystemsAWebcontainercanprovideserver-sidecomponents(suchasservlets)togeneratedynamiccontent5WebApplicationEvolution–JSPPagesservice(req,res)WebContainerServletmethods()RequestJavaBeanforward(req,res)Responsemethods()RequestDispatcherservice(req,res)JavaServerPageSe

6、rvletsgivepoorseparationbetweenbusinesslogicandpresentationlogicUseJavaServerPagesandJavaBeanstoimproveseparation6WebApplicationEvolution–ScalabilityWebWebBrowserContainerHTTPWebServerContainerBusinessrequirementsofteninvolvehighavailabilityImprovedperformancemaybe

7、requiredasbusinessgrowsBoththeserequirementscanbeachievedthroughscalingServerscanprovideredundancyinthesystemBysharingtheloadbetweenservers,performancecanbeenhanced7TheModel-View-ControllerPatternModel-View-Controller(MVC)isadesignpatternVerywidelyusedandregarded

8、asacoreconceptinJ2EEdevelopmentVariouspracticalbenefits(coveredinmoredetaillater)PromotescodereuseReducesdevelopmenttime