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MySQL和JSP的Web那么JSPJSPSQLUMLJSPJSPJSPWebCGIJSPJavaJavaWebOut.println("<HTML>\n<HEAD>\n<TITLE>ThankyouforOut.println("<IMGSRC=\"thanks.jpg\"WIDTH=200HEIGHT=100HTMLservletJavaServer（在微軟方面，成果是活動服務(wù)器頁面。JSP1HTTP2、WEBJSP，JSPJSP是從.jsp種.class.jsp5、一種新創(chuàng)立的類實例被實例化，并發(fā)送_jspServiceSQLHTMLWebJavaHTML。servletWebDMZ安裝方便（10Oracle。MySQLMySQLCREATETABLEUSER(USERIDINTEGER, CREATETABLEPURCHASEUSERIDFOREIGNKEYUSER(USERID),ITEMINTEGER,QUANTITYOraclePURCHASEID3PURCHASEUSERID3MySQL的人們做了一種美麗慷慨激昂的論點有關(guān)在各自的文檔進行數(shù)據(jù)的完整性DBAship把Tomcat和MySQLiPlanetOracleWebSphereSQLServer。GNU（GPL）的人免費提供。（咨詢公司陷入一種不可思議的空間，但至今沒有人方便使用GPL而追逐它們。）原文出處《MySQLandJSPWebapplications》作者：JamesMySQLandJSPWebJSPdevelopersencounteruniqueproblemswhenbuildingwebapplicationsthatrequireintensedatabaseconnectivity.MySQLandJSPWebApplicationsaddressesthechallengesofbuildingdata-drivenapplicationsbasedontheJavaServerPagesdevelopmentmodel.MySQLandJSPWebApplicationsbeginswithanoverviewofthecoretechnologiesrequiredforJSPdatabasedevelopment--JavaServerPages,JDBC,andthedatabaseschema.ThebookthenoutlinesandpresentsanInternetcommerceapplicationthatdemonstratesconceptssuchasreceivingandprocessinguserinput,designingandimplementingbusinessrules,andbalancingtheuserloadontheserver.ThroughtheJDBC(JavaDataBaseConnector),thedevelopercancommunicatewithmostcommercialdatabases,suchasOracle.ThesolutionspresentedinMySQLandJSPWebApplicationscenterontheopensourcetoolsMySQLandTomcat,allowingthereaderanaffordablewaytotestapplicationsandexperimentwiththebook'sexamples.SoWhatIsJSPAllIfyoumeettherequirementsmentioned,youshouldalreadyhaveaprettygoodideawhattheanswertothisquestionis.JSPisallaboutdoinghighlyobject-orientedWebsitesthatcanleverageallthebestpracticesofmodernsoftwareengineering.ThesepracticesincludethingssuchasSQLdatabasesandUML-baseddesign.Thisisn'ttosaythatJSPisacure-allandthatusingitwillautomaticallymakeyourWebsiteaparagonofengineeringart.It'sjustaspossibletodesignbadWebsitesinJSPaswithanyothertechnology.That'swhy,asyougothroughthetext,youwillseehowtoincorporatethebestpracticesandhowtoavoidthepitfallsofconveniencewhenprojectsgetstressful.JSPitselfisanevolutionarystepalongthepaththatstartedwiththefirststaticWebservers,movedthroughCGI-enabledservers,andfinallythefirstgenerationofscript-enabledservers.JSPislessaWebserverwithaJavacomponentthanitisaJavaenginethatunderstandstheWeb.JSPgrewoutofJavaservlets.ServletsallowthedevelopertohandletheincomingWebrequestsusingaJavaprogramthathasaccesstoallthenormalinformationthataCommonGatewayInterface(CGI)programwould.Inaddition,theservlethasaccesstosession-persistentobjects.TheseareJavaobjectsthatareassociatedwithaspecificusersessionandcanbeusedtostorestatebetweenrequests.Servletprogrammingwasamajorstepforwardinallowingdeveloperstowritewell-structuredmodularWebapplicationsusinganobject-orientedlanguage.Italsosolvedtheproblemofstatepersistence,allowingmoreinformationtoresideontheserverduringatransactionandlesstohavetopassbackandforthbetweentheuserandtheserver.Servletsstillsufferedfromonemajorproblem.BecausetheyeventuallyneedtospitoutHTML,theHTMLcodinghadtobeembeddedintheservletcode.Thisledtocodefragmentsliketheoneshownhere:Out.println("<HTML>\n<HEAD>\n<TITLE>Thankyoufor Thiskindofembeddinggetsveryoldveryfastwhenyouhavetocodealotofpages.Inaddition,havingtoescapeallofthequotationmarkscanleadtoalotofconfusingandhard-to-finderrorsifyouleaveoutabackslash.Eventually,astill-betterideaemerged.SupposethatyoucouldcombinethebestofstaticHTMLpagesandwiththeinteractivecapabilitiesofservlets.TheresultwasJavaServerPages(ontheMicrosoftside,theresultwasActiveServerPages).AsFigureI.1shows,JSPisacomplicatedbeast.Inthenextchapter,you'llwalkthroughthisflowindetail,butforthemoment,herearethemajorsteps:ArequestcomesinfromabrowserusingthenormalHTTPrequestTheWebserverhandsofftherequesttoJSP.JSPlooksatthefilenameandfindstheappropriateJSPfile.The.jspfileisconvertedintoa.javafile,containingJavacodethatwillcreateaclasswhosenameisderivedfromthe.jspfilename.JSPthencompilesthe.javafileusingjavactoproducea.classfile.Notethattwopreviousstepsareskippedifa.classfilealreadyexistsandisnewerthanthe.jspAninstanceofthenewlycreatedclassisinstantiatedandsentthe_jspServiceThenewinstancelookstoseeifthereisalreadyaninstanceofthestuff.Userobjectcalleduserexistinginthesessionobjectspaceforthecurrentlyconnecteduser.Ifnot,oneisinstantiated.Aspartofservicingstuff.jsp,theuserinstanceiscalledwiththegetUserName()IftheJSPprocessingrequiresaccesstoinformationinadatabase,itusesJDBCtomaketheconnectionandhandletheSQLrequests.Asyoucansee,atremendousamountofpowerisavailableintheJSPworld.DevelopersarefreetowriteWebpagesthatlookmostlylikeHTML,exceptwherecalloutstoJavaarerequired.But,atthesametime,theyarefreetodevelopfullyfleshed-outobject-orientedapplicationsusingallthefeaturesthatJavacanbringtobear.Theyalsogetallthebenefitsofservlets,includingsessionpersistence.WhyDoWeNeedWell,onereasonissothatLarryEllisonofOraclecanaffordtokeephimselfonProzacwhenhethinksaboutBillGates.Amoreseriousansweristhesamereasonthatdrovemantofirstpressastickagainstapieceofwetmud:becauseit'sgoodtowritethingsdown.Webserversaremarvelouscreatures,butthey'reabitlikeidiotsavants.AskthemtoserveaWebpageorrunapieceofJava,andtheyperformlikeachamp.Butstartaskingthemtorememberwhattheydidfiveminutesago,andtheydevelopamnesiafasterthanacharacterinasoapopera.Thefirstandmostimportantreasonthatyouusedatabasesisthatthere'salotinane-commercetransactionthatyouneedtorememberandtrack:?Auser'sname,address,creditcard,andotherinformationpreviouslyenteredonaregistrationpage?hattheusermighthaveputintoashoppingcartandleftfromaprevious?Whatitemsareinstock,alongwiththeirprice,description,andso?Ordersthatneedtobefulfilled,ordersthathavebeenshipped,anditemsthathavebeenbackordered.Now,youcouldstoreallthisinformationinaflatfileontheserver'sharddisk,butthereareotherimportantpropertiesthatyouwanttohaveforthisdata:?Youwanttobeabletobackoutatransactionifpartofit?YouwanttobeabletolocatethedatasomewheremoresecurethantheWebserver,whichcouldbeinaDMZoroutsidethefirewallaltogether.?Youwanttobeabletoaccessdatasuchasuserdataorproductsquickly,eveniftherearethousandsormillionsofthem.Whenyouaddtheseitemstotheshoppinglist,onlyarelationaldatabasewillreallydothejobeffectively.Manysitesdon'tneedthebattleshipstrength(andpricetag)ofOracle.MySQLisanopen-sourceSQLdatabaseavailableforanyonetouse,withmany(althoughnotall)ofthefeaturesofitsbigbrothers,suchasOracle.MySQLisavailableforjustaboutanycomputerthathasdecentpower—itisfairlylightweightontheprocessorandeasytoinstall(10minutes,asopposedtomultiplehoursforOracle).So,perhapsyouarewondering,what'sthecatch?WhatareyounotgettinginMySQLthatmakespeopleturntoOracle?Well,MySQLisaneatlittlepackage,butitismissingsomethingsthatwouldbenicetohaveinaperfectworld.AmajorfeaturethatMySQLdoesnotofferisdatabaseconsistencychecking.Youcanuseforeignkeytagsinyourschema,butMySQLcheerfullyignoresthem.AlotofDBAsIknowwouldconsiderthisaverybadthing.Aforeignkeyconstraintpreventsyoufromcreatinginconsistentdata.example,let'ssupposethatyouhadaschemethatlookedlikeCREATETABLEUSERUSERID CREATETABLEPURCHASEUSERIDFOREIGNKEYUSER(USERID),ITEMINTEGER,QUANTITYInadatabasesuchasOracle's,ifyoucreatedanentryinthePURCHASEtablewithauserIDof3,therewouldhavetoalreadybeauserIDof3intheUSERtableoranerrorwouldoccur.Similarly,youcouldn'tdeleteuser3fromUSERifitwasreferencedinPURCHASE.TheMySQLfolksmakeaprettyimpassionedargumentintheirdocumentationthatdependingonforeignkeysfordataintegrityisabadideaanyway,butconvincingyourDBAofthisphilosophyislikelytodegradeintoareligiousdebate.Inaddition,someotherfeaturesaremissing,suchassubselectsandselectinto.Butprobablytheothermajorpiecethatyouwillmissistherollback/commitfunctionality.MySQLdoesimplementrollbackandcommitforcertaintypesoftables,butnotallofthem.Again,theMySQLfolksoffertheirownspinonwhythisisokay,butbeingabletorollbacktransactionsis(inmyopinion)importantenoughtomakesurethatyouhaveitavailable.Rollbackallowsyoutosetasavepointonthedatabasebeforestartingtodoaseriesoftransactionswithit,andbeabletoeitherrollbacktotheoriginalstateorcommitthechangesattheend.Forexample,whenrecordingapurchase,youneedtorecordadebitagainsttheuser'saccountandenterarecordintotheshippingtablesothatyou'llknowlatertoshiptheitem.Let'ssaythatthesecondpartfails.Youwouldn'twanttochargetheuserbutnotshiptheitem.Thus,you'dwanttorollbacktothestatebeforethetransactionbegan.So,MySQLisn'tafull-blownproductiondatabase—atleast,notyet.It'sstillgoodenoughforprobably90%ofthee-commercesitesintheworld,however.Andversion4.0,whichisinalphaasofthiswriting,addressesanumberoftheseincludingrow-levellockingandtransactionPuttingTomcatandMySQLCombiningTomcatandMySQLprovidesapowerful,reliable,andfreeplatformthatyoucanusetolearn,develop,anddeployJSPapplications.And,bestofall,thecodethatyoudevelopusingthisplatformwillrunnicelyusingiPlanetandOracleorWebSphereandSQLServer.Asalearningtoolthetwotogetherarealmost"referenceimplementations"oftheirrespectiveprotocols(JSPandSQL).Asaresult,youwon'tpickupanynastyvendor-proprietarybadhabitswhileyou'regettinguptospeed.Inaddition,youcanenjoytheknowledgethatyouaresupportingtheopen-sourcesoftwaremovement.Open-sourcesoftwareiscodethatismadefreelyavailableunderoneofseveralpubliclicenses,frequentlytheGNUGeneralPublicLicense(GPL).FACTSANDFICTIONABOUTTHETheGNUGeneralPublicLicenseisprobablyoneofthemostmisunderstooddocumentsinexistence,Thebasicsbreakdowntothis:IfyouplaceapieceofsoftwareundertheGPL,anyoneisfreetomakeacopyofitineithersourceorexecutableformandgiveittoanyoneelse.IfyoutakeapieceofsoftwareundertheGPLanduseitasapartofyourproduct

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