extending a cics web application using jcics · • fundamentals of using the jcics api ... in the...

ExtendingaCICSWebapplicationusingJCICS

ThiscourseprovidesJavaapplicationdeveloperswithaguidetoCICSservices,demonstratinghowtoaccessthemusingtheJCICSAPI.Topicscoveredinclude:

• FundamentalsofusingtheJCICSAPI• UsingJZOStomapnativerecord-basedlanguagestructurestoJavadatatypes• CommunicatingwithotherCICSprogramsusingaCOMMAREA• LINKingtoaJavaapplicationdeployedinLiberty• AccessingCICSresources,forexampleVSAMandtemporarystoragequeues• ManagingunitofworkscopeinJava• HandlingerrorsinJava

Studentsshouldbefamiliarwiththeconceptsandtechniquesdiscussedin"DevelopingaRESTfulWebapplicationforLibertyinCICS"beforetakingthiscourse.

http://www.redbooks.ibm.com/abstracts/crse0302.html?Open

Section1Lecture1HelloandwelcometotheCICSJavacoursetoextendaCICSwebapplicationusingtheJCICSAPI.MynameisIanBurnettandI’mpartoftheCICSdevelopmentteam,basedintheIBMHursleylabintheUK.

ThiscoursewillshowyouhowtoextendyourknowledgeofJavadevelopmentinCICS,inordertoproducefeature-richapplicationsthatusearangeofCICSfeatures.

Wewillbuilduponknowledgegainedinthe“DevelopingaRESTfulWebapplicationforLibertyinCICS”course,anduseyourexistingdevelopmentenvironmenttoproducemorecomplexJavaapplications.

WewillstartthecoursebylookingatthefundamentalconceptsyouneedtounderstandasaJavadeveloperwheninteractingwithCICS.Usingthesefundamentals,wewillcreateasimplepieceofcodetoinvokeCICSprogramsfromtheLibertyenvironment.

AfterwehaveunderstoodtheprinciplesofinvokingotherCICSprogramstomanipulatedata,wewilllookatseveralresourcesavailableinCICSandstudytheAPIsusedtointeractwiththoseresourcesdirectlyfromJava.

AnotheraspectofCICSapplicationsisthattheyadheretotheACIDpropertiesofatransaction,andtheabilitytodelineateresourceupdatesintounitsofworkisalsoavailabletoJavaapplications.WewilllookathowCICSprovidesunit-of-worksupport,andalsohowthatfitswiththeJCICSAPI.

Developingapplicationsthatareenterprise-ready,requiresrobustprogrammingpracticestogracefullyhandleapplicationandsystemerrors.OurfinaltopicwillbetocovertheconceptsandpracticalitiesofhandlingerrorconditionsusingJava.

OurcodesamplesareavailablefromtheCICSdevGithubrepositoryandprovidefully-workingexamplesofusingtheJCICSAPIsthatwewillbediscussing,alongwithadditionalsupportingmaterial.

TherepositoryshowncontainsmanyJavasourcefilesthatusetheJAX-RSinterface,inordertoprovideasimplemechanismofinvokingJavacodeinaCICSenvironment.AlltheexamplesusetheHTTPGETverb,andreturnJSONdata.RESTfulapplicationswouldtypicallyuseavarietyofHTTPverbs,howeverthesamplecodeisnotintendedasareferenceforthedevelopmentofRESTfulapplications,butmerelytoalloweasytestingusingasimplewebbrowser.

Duringthiscourse,wewillassumethatyouhaveaLibertyJVMserverrunninginCICS.ThesamplecodeprovidedrequiresuseoffacilitiesdefinedbytheJAX-RSspecification,thereforeyourLibertyserver.xmlfileshouldbeconfiguredtoincludethisfeature.

WewillalsoassumeyourworkstationisconfiguredwithadevelopmentenvironmentthatcontainsthenecessaryJCICSJavalibraries.Adynamicwebprojectissufficienttopackagethecodesamples,andforsimplicity,theLibertydrop-insdirectorycanbeusedfordeployment,althoughCICSbundlesmaybeusedifrequired.

Refertothe“DevelopingaRESTfulWebapplicationforLibertyinCICS”courseifyouneedfurtherinformationonconfiguringJavainyourCICSenvironment.

Thank-youforwatchingthiscourse.

Section2Lecture1TheabilityforprogramswrittenindifferentlanguagestocommunicateandshareresourceswhilstrunningasasingletaskisakeystrengthofCICS.AswediscussedinapreviouscoursetheinterfacetoaCICSprogramisdefinedusingeitheraCOMMAREA,orChannelsandContainers.

DifferentlanguagesdefinethelayoutoftheCOMMAREAorcontainerusinglanguagespecificstructures.

TheClanguageallowsfieldstobedefinedwithdatatypessuchascharacters,integersandfloatingpoints.

COBOLprogramsdefinestoragelayoutusingfields,representedbypictureclauses,tospecifythedifferentnumericandcharacterdatatypes.

UsuallytheselanguagestructuresareseparatedoutintoasourcefilereferredtoasacopybookinCOBOL,orasaheaderfileintheClanguage.Inpracticalterms,acopybookoftenrepresentsanentitysuchasanemployeeorastockitem.

Aswellasdescribinginterfaces,alanguagestructurecanalsobeusedtodescribethelayoutofdatastoredinsequentialrecordssuchasVSAMfilesorTemporaryStorageQueues.

TointerfacewithexistingprogramsfromJavaweneedameansofaccessingdatawithinstructuredrecords.

WhenusingtheJCICSAPItolinktoaCICSprogramCOMMAREAdataispassedasabytearray.

UsingthestandardJavalanguageconstructs,itispossibletoconstruct,populate,andreadfromthisbytearraydirectly.However,thereareseveralproblemswiththisapproach.

Firstly,manualbytearraymanipulationistimeconsumingtodevelopanderrorprone.

Secondly,arecordmaycontainanelementinaformatthatisnotnativelysupportedbythestandardJavalibraries.Forexample,packeddecimalfieldsarecommononz/OS,buthavenoJavadatatypeequivalent.

Finally,manipulationofindividualbyteswithinabytearraydoesnotfitverywellwiththeobject-orientedprogrammingmodelofJava.

ThesolutiontotheseproblemsistogenerateaJavabeanfromthecopybookwithaccessormethodswhichgetandsetthefieldsautomaticallyconvertingdataasrequired.

Thegeneratedbeanprovidesamappingbetweentheobject-orientedJavaprogrammingmodel,andtherecordorientatedprogrammingmodel.

Wewillcoverthegenerationofthesebeansinafollowinglecture.

Duringthiscourse,itwillbeusefultouseasamplecopybooktodemonstratehowandwherebytearraysareusedintheJCICSAPI.

ThesamplematerialsprovideanexampleCOBOLcopybookthatdefinesseveralfieldsinan80-byterecord.

Therecordrepresentsanentryinastockwarehouse.Inourapplication,afileisusedtoholdthousandsoftheserecords,representingthetotalstockinventoryforawarehouse.

AsweexploretheJCICSAPIinthiscourse,wewillbeusingthesamplerecordtodemonstratecommunicationbetweenvariousapplicationcomponents.

Lookinginmoredetailatthe80-byterecorddefinedinthesample,wecanseeseveralfields.

Firstly,an8-bytefieldisusedasthepartID,itrepresentstheuniquekeyforthisrecordwithinthestockdatabase.NotwopartswithinthedatabasehavethesamepartID.

Asecond8-bytefieldisusedtorepresenttheIDofthesupplierofthatpart.Thiswouldlikelyreferenceanentryinanotherfile,whichcontainedalistofallthesuppliersused.

Eachparthasaunitprice,thatisdefinedusingthepackeddecimalformat.

Twodatesarestoredintherecord–thelasttimeanorderwasplaced,andthenexttimeanorderwillbeplacedforthispart.

Anumericfieldcontainsinformationaboutthenumberofthesepartsthatarecurrentlyheldinthewarehouse.

Finally,adescriptionofthispartisstoredinthesecondhalfoftherecordintextformat.

Thesupportingmaterialcontainsanothersamplecopybooktorepresentasupplier.Thiswillbeusefullaterwhendemonstratingcaseswhererelationshipsexistbetweenrecords.

Inthenextlecture,wewilllookattheJZOStoolkitandhowtherecordgeneratorcomponentcanbeusedtomapfromoursampleCOBOLcopybooktoanobject-orientedJavaclass.

Section2Lecture2JavarecordsareusedtomapnativerecordbasedlanguagestructurestoJavadatatypes.IBMsuppliestwoJavarecordgenerationtools.

OneoptionistheJ2CrecordimporterprovidedwithIBMDeveloperforzSystemsEnterpriseEditionwithintheJ2Cfeature.

TheotheroptionistheJZOSRecordGeneratorwhichwewilldescribeinthiscourse.

TheJZOSrecordgeneratorcreatesaJavaclass,basedonacopybookfromCOBOLoraDSECTfromassembler.Inourexample,wewillgenerateaJavaclassfromthestockpartcopybookthatwelookedatinthepreviouslecture.GeneratingaJavarecordisatwo-stageprocess.

ThefirststageistocompiletheCOBOLprogramspecifyingtheADATAparametertogeneratetheADATAfile.

ThesecondstageistoruntheJZOSrecordgeneratorusingtheADATAfileasinput,togenerateaJavasourcefile

TheJavasourcefilecanbeincludedinajavaprojectorcanbecompileddirectlyintoaJavalibrary.

IncludingthegeneratedJavasourcefileintheJavaapplicationprojectisusefulwhenthegeneratedcodeneedsfurthercustomizationsuchaschangingencodingsforspecificfields.TodothatrequiresimportingthegeneratedJavasourcefileintoyourEclipsedevelopmentenvironment,andthenaddingtheJZOSlibrarytotheprojectbuildpath.However,iftheCOBOLcopybookchangesandrecordneedstoberegenerated-thiswillrequiredevelopmentefforttoupdatethesourceintheEclipsedevelopmentenvironment.

AnalternativeapproachistocompilethegeneratedsourcefileandpackageitintoaJavaarchive,orjarfile,whichcanbeincludedwiththeJavaapplication.ThisuseofacompiledjarfileavoidstherequirementtoaddtheJZOSlibrariestotheEclipseworkspaceandallowsmultiplerecordstobepackagedwithinasinglelibrary.AnotheradvantageofthisapproachisthatitcanbeautomatedandtheJARfileplacedinarepositoryfordependencymanagement.

Thesampleapplicationthataccompaniesthiscoursefollowsthe“compileandJAR”approach.Itsuppliesalibraryjarfilecontainingacompiledrecordclassthatcorrespondstothestockpartcopybook.

Inthissection,wehavelookedathowtheinterfacetoCICSprogramscanbedefined,andhowJavaapplicationscanuserecordgeneratorstomaptothisinterface.WethenshowedhowtheJZOSrecordgeneratorcouldbeusedtobuildaJavarecordfromthecompilerADATA.Finally,weshowedhowtopackagetheJavarecordintoalibraryfordistributiontodevelopers.

Inthenextsection,wewilllookatusingthisgeneratedrecordwhenlinkingtoaCICSCOBOLprogramfromaJavaapplication.

Formoredetailsonthesesteps,includingaworkedexamplewithcompleteJCL,havealookatthe“BuildingJavarecordsfromCOBOLwithIBMJZOS”ontheCICSdevelopercenter.

Thankyouforwatching.

Section3Lecture1Inthe“DevelopingaRESTfulWebapplicationforLibertyinCICS”course,welookedattheconceptofaCICSprogram.

Aprogramisaunitofcompiledcodethatprovidesapplicationlogic,andcanbedevelopedusingoneofmanylanguagessupportedintheCICSenvironment,includingJava.

TheterminologyusedwhencallingfromoneCICSprogramtoanotherisknownasalink.Thelinkcommandpassescontroltothetargetprogramandwaitsforittocomplete.

AlinkdiffersfromaJavamethodcallinthatthetargetprogramcanbeimplementedinanylanguagesupportedbyCICSandcanalsoresideonadifferentCICSsystem.

AJavamethodcallhoweverisconsiderablymorelightweightthanalinkcommand

WhenusingtheJCICSAPI,firstcreateaninstanceoftheProgramclass,andspecifythenameofthetargetprogramusingthesetName()method.

Toissuethelinksimplyinvokethelinkmethodontheprogramobject.Herewedonotpassanyargumentsonthelinkmethodsonodataispassedtothetargetprogram.

Whencommunicatingfromoneprogramtoanother,therearetwomainwaystopassdata---eitherthroughtheuseofacommarea-orthroughtheuseofchannelsandcontainers.

Nowlet’slookatpassingacommareaonalinkcommand

Acommareaisanareaofmemoryusedtopassdatabetweentwoprograms.

FromaCICSperspective,acommareaisjustasequenceofbytes,CICSdoesnotattempttoformatthedatastructureandjustfacilitatesthetransferofthedatabetweentheprograms.

Thedatastructureisdescribedusinganinterface,wherethefieldsaredefinedusingalanguagespecificstructuresuchasaCOBOLcopybookaswediscussedinthepreviouslecture.

ForaJavaapplicationtocommunicatewithanapplicationwritteninanotherlanguagewecanuseabytearraytorepresentthecommareaandtoholdthedatatobetransferred.Asnotedintheprevioussection,generatedJavaclassescanbeusedtomoreeasilyconstructtherequiredbytearray.

Inthisexample,welookatpassingasinglerecordfromourJavaapplicationintoanexistingCICSprogramusingtheCOMMAREAinterface.Thisrecordisdefinedbythestandardstockpartrecordformatcoveredearlier.

WhenusingtheJZOSrecordgeneratortooling,wecalledourgeneratedclass“StockPart”.So,ourfirsttaskistocreateaninstanceofthisclass,andpopulateitwithrelevantdata.

TheJZOSrecordgeneratortoolingdefinesgetterandsettermethodsintheJavaclass,thenamesofthesemethodscorrespondtothefieldsoftheoriginalCOBOLcopybook.

GetterandSettermethods,otherwiseknownas“accessor”methods,allowaJavadevelopertouseanobject-orientedapproachwhenbuildingarecord.

OncetheJavaobjecthasbeeninstantiated,wecanconvertitintoabytearrayusingthegetByteBuffer()method.Thisreturnsaserializedversionofthestructuredrecorddefinedintheoriginalcopybook.

Nowthatwehavethedataready,wecanusethistolinktothetargetprogram.

WecreateanewinstanceoftheProgramclass,andspecifythenameofthetargetprogramthatwewishtoLINKtousingthesetName()method.

Wetheninvokethelinkmethodonourprogramobject-thistimepassingtheStockPartbytearray

Onsuccessfulreturnfromthetargetprogram,anyupdatestothecommareawillbereflectedinthebytearray.

Here,wetaketheupdatedbytearrayandconstructanewStockPartobjecttorepresentthereturneddata.Subsequentcodemaythenreadvaluesfromthisnewly-constructedobjectusingtheaccessormethods.

Acommareaisabidirectionaltransfermechanism,andprogramscanusethisareatosendanyformatofdataineitherdirection.OurpreviousexamplesentarecordintheStockPartformat,andreceivedarecordinthesameformat.

Withalargeenoughdataarea,anyrecordformatcanbereturned.

Inthisexample,weuseaStockPartobjecttoconstructabytearraythatwillbepassedtoatargetprogram.Whencalled,thatprogramwilllookupthesupplierrecordandpopulatethecommareawitharecordformatdetailingthesupplierofthatpart.

HavingpreviouslycreatedasuitableJZOSclasstomaptherecordforasupplier-whenthelinkmethodcompletes-wecangenerateanewinstanceofthesupplierobjectfromthereturnedbytearray.Theresultingobjectcanbequeriedforthesupplierinformation.

CICSoffersanoptimizationonalinkcommandbyspecifyingthesizeofthedatatothetargetprogram-abenefitalsoavailablefromtheJCICSAPI.

Asanexample,apartlookuproutinemayonlyneeda8-bytepartnumberasinput,butwillrequirean80-bytecommareatoreturnthedata.Specifyingtheoptionalintparameterafterthebytearrayallowsthecallertospecifythedatalengthusedonthesend.

Inthisexample,abytearrayoflength80iscreatedbythecallingprogram,butthedatalengthisspecifiedas8.WhenCICSpassescontroltothetargetprogram,onlythefirst8bytesaretransmitted.Theremainderofthe80-bytecommareaispaddedwithzeroes.Whenthetargetprogramreturns,all80-bytesaresentbacktothecallingprogram.

ThisoptimizationcanbeusedtoreduceCPUandresponsetimes,especiallywherelargecommareasarerequiredforreturnvaluesorwherelinksflowbetweenCICSsystems.

RecallthattheothermethodofpassingdatafromoneprogramtoanotherisbyChannelsandContainers.Achannelisaconduitbetweenprograms,ittypicallyholdsoneormorecontainerstobepassedbetweentheprograms.Acontainerisanamedblockofdata.

Channelsandcontainersoffertheadvantagethatmorethan32KBofdatacanbepassed.Bycontrast,commareasareconfinedtoa32KBlimit.

Multiplecontainerscanbepassedbetweenprogramswithinachannel.Achannelisthereforeanalogoustoaparameterlist.

AworkedexampleofusingchannelsandcontainersinJCICSisavailableinthe“DevelopingaRESTfulWebapplicationforLibertyinCICS”course.Thesamplematerialsforthiscoursealsocontainanexampleofusingchannelsandcontainerstopassdata.

ThislecturehaslookedatthewaysinwhichtheJCICSAPIcanbeusedtoLINKtoanotherCICSprogram.

ThesamplesourcecodeprovidedwiththiscoursehasexamplesofalltheJCICScommandscoveredinthislecture.

ThenextlecturewilllookathowwecanlinkfromaCICSprogramintoaJavacomponentinaLibertyJVMserver

Section3Lecture2WebSphereLibertyprovidesaJavaEnterpriseEditionorJavaEEplatform,andisdesignedtohelpdeveloperscreatelarge-scaleenterpriseapplications.

UsingLinktoLiberty,anyCICSprogramcannowcallJavaEEapplicationsinaLibertyJVMserver.

TheCICSLINKcommandcaninvokePlainOldJavaObjects(POJOs)thathavebeendeployedinsideaWebapplication...justasiftheywereanyCICSprogram.

ToachievethisseamlessLINK,aCICSdefinedJavaannotationisappliedtoaJavamethodwithintheLibertyapplication.TheannotationindicatesthatthemethodshouldbeexposedastheentrypointforaCICSJavaprogram

WhentheapplicationisinstalledCICSwilldetecttheannotationmeta-dataandautomaticallycreateandinstallaPROGRAMresourceforeachentrypointdetected.

OncethesePROGRAMresourceshavebeencreated,thenaCICSapplicationwritteninanylanguagecanusetheLINKcommandandinvokethedesiredJavamethodpassingachannelastheinterface.Notethatacommareacannotbepassedinthisscenario.

Inthisexample,wehaveaclassorPOJOinaWebapplicationthatexposesthegetSupplierInfo()methodasanentrypoint.The@CICSProgramannotationisusedtoindicatethismethodshouldbemadeavailableasaPROGRAMresource.Whentheapplicationisinstalled,aCICSprogramresourcenamedGETSUPPLisautomaticallycreated,andisreadytobeinvoked.

DataispassedbetweencallingprogramandtheLibertyapplicationusingChannelsandContainers.

WithinthetargetJavamethod,JCICSisusedtogetareferencetothecurrentchannelandtoobtainthedatafromcontainersprovidedbythecaller.

Oursamplecodeprovidesacompleteimplementationofthegetsupplierinfomethod.ThesamplecodecouldbeextendedtouseJavaEEcapabilitiessuchasJAX-RSclientAPItorequestinformationfromasupplierusingaremote,RESTfulwebservice.

FromtheperspectiveofthecallingCOBOLapplication,ithasusedtheCICSLINKcommandtoinvokeanamedprogrampassingindataviaacontainer,andreceivedaresponseusingaCOBOLstructure.

ThePOJOcomponentinthewebapplicationwasabletoreceiveandprocessthecontainersandexploitJavaEE7functionality.

Inthissection,wehavelookedathowwecanlinktootherCICSprogramsusingmethodsontheJCICSProgramclass.

Usingourgeneratedrecord,wepasseddatatoexistingCICSapplicationsusingthecommareainterface.Thealternativemethodofpassingdatabetweenprograms-theCICSchannelsandcontainerssupport-wascoveredinthe“DevelopingaRESTfulWebapplicationforLibertyinCICS”course.

Finally,welookedathowCICScanmakeLibertyapplicationsavailabletotraditionalprograms,usingtheLinktoLibertycapability.

Inthenextsection,wewilllookathowtoaccessotherCICSresourcesusingtheJCICSAPI.

Section4Lecture1CICSprovidesaccesstoarangeofresourcetypes.SomeoftheseresourceslikeTemporaryStorageQueuesareuniquetoCICS,whileotherssuchasVSAMfilesarecommonacrossz/OS.Inthissection,wewillbelookingataccessingtheseresourcesusingtheJCICSAPI.

We'llcometotheCICS-specificresourcesshortly,butfirstlet’sstartwithVSAMfiles.

InCICS,datamanagementservicesaretraditionallyknownasCICSfilecontrol.CICSfilecontroloffersyouaccesstodatasetsthataremanagedbytheVirtualStorageAccessMethod,orVSAM.

Basicdirect-accessmethod,orBDAM,datasetsarenotsupportedbytheJCICSAPI,sothislecturewillfocusonVSAMfiles.

CICSfilecontrolletsyouread,update,add,delete,andbrowsedatainVSAMdatasets.YoucanalsoaccessCICSshareddatatablesandcouplingfacilitydatatablesusingthefilecontrolAPIs.

FilesmaybesharedbyapplicationswithinaCICSregion,oracrossthewiderz/OSsysplex.

ACICSapplicationprogramreadsandwritesitsdataintheformofindividualrecords.EachreadorwriterequestismadebyaCICScommand.

Toaccessarecord,theapplicationprogrammustidentifyboththerecordandthedatasetthatholdsit.

Thereareseveralmethodsthatcanbeusedtoidentifyarecord–whichonetousedependsonthetypeofVSAMfileinuse.WewilllookatthedifferenttypesofVSAMfilelater.

AnapplicationusesaCICSfileresourcetoidentifyadataset.ThisfileresourcehasauniquenamewithintheCICSregion,allowingtheapplicationtoremainagnosticoftheunderlyingdatasetname.

Itisnotnecessaryforanapplicationtoopenorcloseafileexplicitly,CICSmanagestheresourceonbehalfofallapplications.

Inthisdiagram,anapplicationaccessesaVSAMfileusingCICSfilecontrol.

TheapplicationidentifiesthedatasettobeusedbyreferencingtheCICSFILEresourcenamedSTOCK1.

TheSTOCK1fileresourceisdefinedtoreferencetheMVSdatasetTESTdotDATAdotSTOCK.

Theapplicationcouldlaterbedeployedintoadifferentsystem,whereafileresourceofthesamenamereferencesadifferentMVSdataset.

CICSsupportsaccesstothefollowingtypesofVSAMdataset:

• Key-sequenceddataset,orKSDS• Entry-sequenceddataset,orESDS• andRelativerecorddataset,orRRDS

Akey-sequenceddatasethaseachofitsrecordsidentifiedbyakey.Thekeyofeachrecordisafieldinapredefinedpositionwithintherecord.Eachkeymustbeuniqueinthedataset.

Anentry-sequenceddatasetisoneinwhicheachrecordisidentifiedbyitsrelativebyteaddressoroffset.

Arelativerecorddatasethasrecordsthatareidentifiedbytheirrelativerecordnumberororder.

TheVSAMdatasetstopicintheIBMKnowledgeCenterhasamorecomprehensivedescriptionofthesedifferentVSAMdatasets.

Ourexamplewilluseakey-sequenceddataset.

BeforewecanuseVSAMfiles,weneedtodefinethedatasetusingthez/OSutilityIDCAMS.

TheexampleshowssomesampleinputtotheIDCAMSutilitytodefineaVSAMfilenamedTEST.DATA.STOCK.WewillusethisdatasetinourexampletostorestockinformationfromtheStockPartrecordwegeneratedusingJZOSearlier.

Therecordskeywordindicatestheamountofspacethatthedisksubsystemneedstoreserveforthedataset,whiletheINDEXEDkeywordspecifiestheVSAMdatasetistobeusedforkey-sequenceddata.

TheKEYSkeywordspecifiesthateachrecordhasauniquekeythatiseightbytesinlengthandbeginsatoffsetzero.ThismatchestheSTOCKPARTrecordwedefinedearlier.

Finally,theRECORDSIZEkeywordspecifiesthatonaverage,eachrecordwillbeeightybytesinlength,withamaximumlengthofeightybytes.WhileVSAMfilessupportvariable-lengthrecords,oursimpleapplicationonlyusesfixed-lengthrecords.

Forthefullexample,seetheaccompanyingsampleprojectmaterialsinGithub.

Asdescribedearlier,aCICSapplicationisabstractedfromthephysicaldatasetsitusesbymeansofaCICSFILEresource.Inordertouseoursampleapplication,youwillneedtodefineandinstallaFILEdefinitionintotheCICSregion.

Forthisexample,mostofthedefaultswillbesuitable,withsomeexceptions.

Thefileresourcedefinitionrequiresanameofuptoeightcharacters–thesamplecodeusestheSMPLXMPLname.

IfyoudonotspecifythefileasaDDstatementinyourCICSstartupjob,youwillneedtospecifythephysicaldatasetnameusingtheDSNAMEattributeonthedefinition.

TofullydemonstratetheJCICSfilecontrolAPI,youshouldsetalloftheadd,browse,delete,read,andupdateattributestoyes,otherwiseCICSwillthrowanexceptionwhentheapplicationattemptstoperformanoperationthatisnotpermitted.

NowwearegoingtodevelopthewebapplicationtoaccesstheVSAMfile.

ThesampleclassVSAMKSDSfileresourceprovidesanumberofmethodstodemonstratethevariousaspectsofaccessingaVSAMfile.

Thesimplestofthesemethodsisthe“writenewrecord”methodwhichcreatesanewstockpartandaddsittotheVSAMfile.

Aswiththeexamplesinthe“DevelopingaRESTfulWebapplicationforLibertyinCICS”course,weuseasimpleRESTfulinterfacetoinvoketheJavacode.

TheCICSApplicationclassspecifiesabaseapplicationpathof“rest”,thereforeanyRESTfulresourcesaccessedinthiswebapplicationwillusethisstringasarootURI.

TheVSAMKSDSfileresourceclassspecifiesarelativeresourceURIofksdsusingthePathannotation,whilethewritenewrecordmethodspecifiesapathof“write”relativetotheparentresource.

Forthewritenewrecordmethod,wewouldthereforeusetheURI“rest/ksds/write”relativetothebaseURIoftheapplicationwheninstalledintoCICS.

OnlytheHTTPGETverbisrecognizedinthisapplication,asindicatedbytheGETannotationonthemethod.

ThewritenewrecordmethodreturnsaStockPartCollectionobject,whichisserializedtoJSONasdirectedbytheProducesannotationontheclass.TheStockPartCollectionobjectisasimplewrapperobjectthatcontainsalistofStockPartobjects.

TocreatearecordsuitableforinsertionintotheVSAMfile,thegeneratemethodinthestockparthelperclasscreatesaninstanceoftheJZOS-generatedStockPartclassandpopulatesitwithsampledata.

ThewritenewrecordmethodtakesthegeneratedrecordandconvertsthistoabytearrayusingtheJZOSgetbytebuffermethod.

Anothermethodinthestockparthelperclassextractstherecordkeyasabytearray.Recallthatthekeyforthestockpartrecordiseightbytesinlengthandbeginsatoffsetzero.ThehelperclassobtainsthebytearrayfromtheStockPartobjectandextractsthefirsteightbytesasanewbytearray.

Inthisexample,weareaccessingakey-sequenceddataset,orKSDSfile.ToreferencethisfileusingJCICS,wecreateaninstanceoftheKSDSclassandspecifythenameoftheCICSfileresource.

ThewritemethodontheKSDSclasstakestwobytearraysasparameters–thekeyandtherecordforwriting.

TheCICStransactionwouldautomaticallybecommittedonnormalcompletionoftheCICStask,butasasimpledemonstrationofmanagingunitsofwork,thesampleapplicationusestheTaskcommitmethodtoexplicitlycompletethecurrentunitofwork.

Finally,thequeryfilemethodisinvoked,whichreturnsaninstanceofthestockpartcollectionclass.

Thequeryfilemethodperformsafilebrowseoperation,startingattheveryfirstrecordinthefile,andreadingeachrecordintomemory.Eachrecordisconvertedtoastockpartobjectandaddedtothestockpartcollectioninstance.WhenserializedtoJSON,thisprovidesasimplemeansofviewingthecontentsofthesampleVSAMfileandhowitisaffectedbyeachfilecontroloperation.

Forclarity,thenecessaryerror-handlinglogichasnotbeenincludedhere,butisprovidedinthesamplecode.Wewillcovererror-handlinglaterinthecourse.

TheupdateRecord()methodprovidesanexampleofupdatingarecordinaVSAMfile.

Firstly,theKSDSfileisreferencedbycreatinganewinstanceoftheKSDSclass,aspreviouslydoneinthewritenewrecordmethod.

Toreaddatafromafile,arecordholderobjectisrequired.ThereadforupdatemethodontheKSDSclassisthencalled,passinginthreeparameters.

ThefirstparameteristhekeyoftherecordthatwewishtoreadfromtheVSAMfile.Inthiscase,wesupplyakeyofallzeroes,createdusingamethodinthestockparthelperclass.Akeyofallzeroesisusedinourapplication,simplytoobtainthefirstrecordintheabsenceofrealdata.

Thesecondparameterspecifiesthattheapplicationwillreadtherecordwithakeyequalto,orgreaterthan,thekeysupplied.

Thefinalparameteristherecordholderinstance,whichwillbeusedtoreceivethedatathatresultsfromtheVSAMfilereadoperation.

Onsuccessfulcompletionofthereadforupdatemethod,therecordholderinstancewillcontainabytearrayrepresentingtherecordinthedataset,aslocatedbythespecifiedkey.Thegetvaluemethodextractsthisbytearray,anditispassedtotheconstructorofthegeneratedstockpartclass.

Asecondstockpartinstanceiscreatedusingthegeneratemethodwecoveredearlier.Thepartid,orkey,fromthereadrecordiscopiedintothenewly-generatedrecord.Thisstepisusedasasimpledemonstrationofwherebusinesslogicwouldamendvaluesinareal-worldapplication.

WethenupdatetherecordintheVSAMfilebycallingtherewritemethod,supplyingthefullrecordasabytearray.

Notethatforarewriteoperation,wedonotneedtosupplythekey,asthiswasestablishedonthepreviousreadforupdateoperation.

Finally,weexplicitlycallthetaskcommitmethodtoreleaseanylocksweholdagainstthefile.

Whenexecutingthesamplecode,repeatedlyaccessingtherest/ksds/updatemethodbypressingrefreshinyourbrowserwillshowthefirstrecordinthefilebeingupdatedwithnewsampledata.

ThedeleterecordmethodintheVSAMKSDSfileresourceclassprovidesanexampleofdeletingarecordinaVSAMfile.

Theflowofthemethodisverysimilartotheupdaterecordexample,withareadforupdateoperationfindingthecorrectrecord,andthenthedeletemethodbeingcalledtodeletetherecordfromthefile.

Inthislecture,wehavelookedathowwecanusetheJCICSAPItoaccessVSAMKSDSfiles,usingourgeneratedJZOSclasstoprovideanobject-orientedmeansofaccessingstructuredrecordsondisk.ManyoftheconceptscoveredhereareequallyapplicabletoESDSandRRDSfiles.SeetheJCICSJavadocdocumentationforacompletereferenceonthesyntaxrequiredtoaccessthesetypesofVSAMfiles.

Inthenextlecture,wewilllookathowJavaapplicationscanaccessCICStemporarystoragequeues.

Section4Lecture2

CICStemporarystoragequeues,orTSQs,areameansofstoringasequenceofdataitems.

DatainaTSQcanbestoredinmainmemory,ondisk,knownasauxiliaryTSQs,orsharedviathesysplexcouplingfacility.

ThedataitemsinaTSQhaveamaximumsizeofjustunderthirtytwokilobytes,andcanbeaccessedinanyorder

TSQsarereferencedusinganameofupto16charactersinlength.Theycanbedefinedasbeingrecoverableornon-recoverableCICSresources.

Temporarystoragequeuesdonotneedtobedefinedinadvanceofanapplicationusingthem,andcanbeusedtosharedataacrossapplications.

SupportfortemporarystoragequeuesisprovidedintheJCICSAPIbyusingtheTSQclass.

InoursampleweareusingaTSQfromwithinaCICSLibertyWeb-applicationandbecauseHTTPrequestsarestateless,we'llneedsomemeansofpersistingtheTSQnameacrossmultipleHTTPrequests.

Toprovideasimple-to-usemethodofaccessingthesametemporarystoragequeuefromabrowseracrossmultiplerequests,thequeuenameisstoredinanHTTPsessionobject.

EverytimeabrowserissuesaGETrequestagainstthetemporarystorageresourceclass,thegetqueuemethodextractsthequeuenamefromtheHTTPsessionobject,andreturnsaJCICSTSQobjectthatcorrespondstothecorrectqueueforthatbrowsersession.

Examiningtheflowinmoredetail,thefirsttimeabrowseraccessesthesampleapplication,itissuesanHTTPGETrequestagainsttherestslashtsqslashwriteURI,andhasnocookietokentosendtotheserver.Thegetqueuemethodintheapplicationfindsnocookiehasbeensent,andhencenoHTTPsessionispresent.

Thegeneratequeuenamemethodisinvokedtocreateanew,uniquequeuename.ThisqueuenameisstoredinanHTTPsessionobject,whichispersistedautomaticallybytheLibertyruntime.

Thewritenewrecordmethodwillwriteanelementtothisnewqueue,andthenreturntotheclient.WhentheLibertycontainersendstheJSONresponsebacktothebrowser,italsoincludesanHTTPsessioncookieaspartoftheflow.

SubsequentrequestsfromthebrowserwillflowthisHTTPsessioncookietotheapplication,andthiscookieisusedbytheLibertyserverasakeytoretrievetheHTTPsessionobjectthatcorrespondstothebrowserinstancemakingtherequest.

BeforeweexaminetheJCICSAPIindetail,let’stakeabrieflookatsomeofthesamplecode’shelpermethods.

Thenameofthequeueusedbyoursampleapplicationiscreatedbythegeneratequeuenamemethod.Thiscreatesaqueuename,basedonaknownprefixandthecurrenttime.

ThesampletemporarystorageresourceclassprovidesexamplesofaccessingaTSQusingtheJCICSAPI,

Thewritenewrecordmethoddemonstrateshowtowriteasingleelementtoatemporarystoragequeue.

HereweusethegetqueuemethodtoobtainaninstanceoftheJCICSTSQclass.

ThisTSQobjectreferencestheCICStemporarystoragequeuethatisinusebythecurrentbrowsersession,usingthemechanismdescribedearlier.

AsamplerecordiscreatedusingthestockparthelperclasswecoveredwhenlookingatVSAMfileaccess,andabytearrayisobtainedusingtheJZOSgetbytebuffermethod.

WritingasingleelementtoaTSQisachievedbysimplycallingthewriteitemmethod,passingthedatatobewrittenasabytearray.

InasimilarmannertotheVSAMexamples,astockpartcollectionobjectisreturnedbythemethod,andisserialisedbytheLibertyserverasaJSONresponse.

Thiscollectionobjectiscreatedbythequeryqueuemethod,whichperformsabrowseacrossthequeue,addingeachqueueelementtothecollection.

Therearetwoimportantpointstonotefromthequeryqueuemethod.

Thefirstisthatelementsinatemporarystoragequeuearenumberedfromelementone,unlikemanyconstructsyoumaybeusedtoinJava.

ThesecondisthatitemsarereadfromaTSQusinganItemHolderinstance.ThisitemholderobjectperformsasimilarfunctiontotherecordholderwediscussedearlierforVSAMfiles.

AsinthepreviousVSAMexample,theupdaterecordmethodwillupdatethefirstelementinthequeue.

ThegetqueuemethodisagainusedtoobtaintheTSQcorrespondingtothecurrentbrowsersession,andanewsamplestockpartrecordiscreatedusingthestockparthelperclass.

TheTSQisupdatedthroughtheuseoftherewriteitemmethodintheTSQclass,whichtakestwoparameters–theitemindexandthenewdatatowritetothequeue.

Afterupdatingthequeue,ourqueryqueuemethodiscalledtoreturnthecontentsofthequeueasaJSONresponse.

Individualelementscannotbedeletedfromatemporarystoragequeue–itisonlypossibletodeleteanentirequeue.

ThedeletemethodintheTSQclasstakesnoargumentsanddeletesthecorrespondingtemporarystoragequeue.

ThedeletequeuemethodinoursamplecodegivesasimpleexampleofobtainingaTSQobjectandthendeletingtheunderlyingqueue.

Inthislecturewehavecoveredthebasicconceptsofatemporarystoragequeue,andlookedathowwecanusetheJCICSAPItoaccessthesequeuesfromJava.

Thankyouforwatching.

Section4Lecture3

Oneofthefundamentalconceptsoftransactionprocessingisthatresourceupdatesadheretotheatomicity,consistency,isolation,anddurabilityprinciples,commonlyknownastheACIDpropertiesofatransaction.

Resourcesaccessedbyaprogramaremanagedwithinatransactionalscopeknownasaunitofwork.AllrecoverableresourcesaccessedwithinasingleunitofworkareupdatedaccordingtotheACIDprinciples.

Aunitofworkmayeithercompletesuccessfully,knownasacommit,orunsuccessfully,knownasarollback.

InaCICStask,anactiveunitofworkisalwayspresent.

AunitofworkbeginsautomaticallyatthestartofaCICStask,beforecontrolispassedtotheapplication.UponsuccessfulcompletionofaCICStask,theunitofworkisautomaticallycommitted.

IfaCICStaskterminatesabnormally,thentheactiveunitofworkisrolled-backandanyupdatestorecoverableresourcesareundone.

UpdatestorecoverableCICSresourcesmadefromJavaapplicationswillbesubjecttothesameunitofworkconstraintsasotherCICSprograms.

Itisalsopossibleforanapplicationtomangetheunitofworkboundaries.

TheJCICScommitandrollbackmethodsintheTaskclasscanbeusedtocompletethecurrentunitofworkandupdateresourcesaccordingly.

OncethecurrentunitofworkhasbeencompletedinCICS,anewunitofworkisautomaticallycreated,ensuringthatanyresourceupdatesalwaysoccurwithinaunitofwork.

Wherelargenumbersofresourcesarebeingupdatedinlong-runningtasks,iftheapplicationdesignpermits,itisrecommendedthatunitsofworkarecommittedperiodically.Thiswillreducethenumberofoutstandinglocksthatareheldbytheapplication,andpotentiallyimproveoverallsystemthroughput.

ThewritenewrecordmethodinourVSAMsampleshowsanexampleofexplicitlycommittingthecurrentCICSunitofwork.

Inthissection,wehavelookedatthecharacteristicsofseveralCICSresources,andhowtoaccessthemusingtheJCICSAPI.

InthislecturewecoveredtheCICSsupportforunitsofwork,andhowapplicationscancontrolthescopeofupdatestorecoverableresources.

Inthenextsection,wewilllookathowJavaapplicationscansuccessfullyhandleapplicationandsystemerrors,inordertoproducemorerobustapplications.

Oursampleapplicationcodeprovidesexamplesofaccessingkey-sequencedVSAMfiles,CICStemporarystoragequeues,andalsoCICStransientdataqueuesusingJCICS.

Thankyouforwatching.

Section5Lecture1

Itisimportanttoprovidegooderror-handlinglogicinenterprise-classsoftwaretogracefullyhandlearangeofapplicationandsystemproblems.

Inthissection,wewilllookathowJavahandleserrorsingeneral,thenapplythatknowledgetotheJCICSAPI.

Duringexecutionofanapplication,variouserrorconditionsmayarise.Theseerrorconditionsmayhavemanyrootcauses,butfundamentallytheycanbecategorisedintothreemaintypes:expectederrors,unexpectederrors,andfatalerrors.

Expectederrorsareconditionsthatcanbereasonablyforeseenbyanapplicationdeveloper.Forexample,attemptingtoreadanon-existingrecordfromaVSAMfileislikelytobeaconditionthattheapplicationisexpectedtohandle.

Unexpectederrorsareconditionsthatmayoccur,butarenotnormallyexpectedtobehandledbytheapplication.Forexample,aprogrammayattempttoaccessanelementofaJavaarraywhichdoesnotexist.Thisprobablyrepresentsaprogrammingerror,andasaresult,theapplicationislikelytobeinanindeterminatestate.

Fatalerrorsarethemostseriousofallerrorconditions,andusuallyrepresentasituationfromwhichanapplicationisunlikelytobeabletorecover.AnexampleofafatalerroroccurringwouldbeiftheJavavirtualmachinefailedtoloadaJavaclassrequiredbyanapplication.

ErrorconditionsintheJavalanguagearemanagedusingtheexceptionmechanism.

IfaJavamethodencountersanerrorcondition,thenaspecialJavaobjectcalledaThrowableiscreatedtocapturethestateofthecurrentthreadatthetimeoftheerror,andthisobjectispropagatedtothecallerofthecurrentmethod–aprocessknownasthrowinganexception.Correspondingly,handlingtheerrorconditionisknownascatchinganexception.Acallingmethodusesatrykeywordtoindicatethescopeoftheerrorhandlinglogic.

TheJavalanguagespecifiesthattheobjectsusedwhenpropagatingexceptionsmustbeinstancesofatypewhichextendstheThrowableclass.TheThrowableclassitselfhastwodirectsubclasses–ExceptionandError.Therearemanysub-classesofException.However,theRuntimeExceptionsubclassisaspecialcaseandisnotclassifiedasacheckedexceptionasitrepresentsunexpectedruntimeerrors.

Together,thecheckedexception,runtimeexception,anderrorclassesrepresenterrorconditionsinJavacodethatcorrespondtotheexpected,unexpected,andfatalerrorcategoriesthatwecoveredearlier.

InJava’serrorhandlingmechanism,expectederrorsextendtheExceptionclass,andareknownascheckedexceptions.

TheJavalanguagespecifiesthatanymethodwhichcanthrowacheckedexceptionmustdeclarethisaspartofthemethodsignature,usingthethrowskeyword.

AnyJavacodewhichcallsamethoddeclaredasthrowingacheckedexceptionmusteitherprovidelogictocatchthecheckedexception,oraddtheexceptiontoit’sownmethodsignature,inordertopropagatetheexceptionfurtherupthestack.

Theconstraintsoncheckedexceptionsareenforcedatcompiletime,andfailuretoadheretothespecificationwillresultinacompilationerror.

UnexpectederrorconditionsarerepresentedbyJavaclasseswhichextendtheRuntimeexceptionclass,andareknownasuncheckedexceptions.

Uncheckedexceptionsarenotsubjecttothecompiletimecheckingmandatedforcheckedexceptions,althoughtheycanbecaughtifrequired.

FatalerrorconditionsarerepresentedbyJavaclasseswhichextendtheErrorclass.ItisconsideredpoorprogrammingpracticetocatchanyexceptionsthataresubclassesoftheErrorclass,astheserarelyrepresentaconditionfromwhichtheapplicationwillbeabletorecover.

NowletstakealookathowCICSerrorhandlingismanagedforCOBOLandotherhighlevellanguages.

TheselanguagesthatusetheEXECCICSAPIhavethreechoiceswhenhandlingerrorconditions:onaper-commandbasis,usingaconditionhandler,orusinganabendhandler.

IfaCICScommandproducesanerror,thenitwillfirsttrytoreturnaresponsecodetotheapplicationusingthedataareasuppliedintheRESPparameteroftheCICScommand.

IfaRESPparameterhasnotbeensupplied,thenCICSwillsearchforanactiveconditionhandler.ConditionhandlersareregisteredinadvanceusingtheEXECCICSHANDLECONDITIONcommand,andperformsomeformofapplication-specificrecoveryoperation.

Ifnoactiveconditionhandlerisfound,thenCICSwillabnormallyend,orabendthetask.TherearemanytypesofCICSabendsdefined,eachcorrespondingtoaspecificerrorcondition,andabendsareclassifiedbytheirfour-characterabendcode.

Whenanabendoccurs,CICSwillsearchforanactiveabendhandlerthatmatchesthegeneratedabend.Similartoconditionhandlers,anabendhandlerroutineisregisteredinadvanceusinganEXECCICSHANDLEABENDcommand.

Ifanactiveabendhandlercannotbelocated,thenCICSwillabnormallyterminatethecurrenttask,whichinturnwillrollbackanyuncommittedupdatestorecoverableresourcesinthecurrentunitofwork.

NowletsconsiderhowCICSerrorsmaptotheJCICSAPI.

TheJCICSexceptionhierarchyincludesuncheckedexceptions,checkedexceptions,andfatalerrors.

ThekeytothemappingbetweenCICSerrorsandtheJCICSexceptionhierarchyisunderstandingwheretheseexceptionscouldbethrown,howtheymaptotheCICSresponsecodes,andwhatactionyoushouldtakeasanapplicationdeveloper.

Let'sstartbylookingatcheckedexceptions.

HereweseethekeyclassesinvolvedintheJCICSexceptionhierarchy.MostJCICSmethodsaredefinedasthrowingcheckedexceptions,andthesecheckedexceptionsrepresentthemajorityofconditionsthatanapplicationmaybeexpectedtohandle.

EacherrorconditionfromaCICScommandismappedtoanexception,andthisexceptionisasubclassoftheCICSconditionexception.

Asanexample,theCICScommandtoreadanelementfromatemporarystoragequeuemayreturnanITEMERRORconditiontoindicatethequeuedidnotcontaintheelementrequested.

IntheJCICSAPI,anelementisreadfromtheTSQusingthereaditemmethod.Thismethodsignaturedeclaresitmaythrow(amongstothers)anItemErrorException,whichistheJCICSAPIequivalentoftheITEMERRORcondition.

SeethequeryqueuemethodinthetemporarystorageresourcesampleclasstoseehowtheITEMERRORandQIDERRconditionsarehandledasexpectederrors,whileanyothererrorconditionresultsinafailureoftherequest,

ThereareonlyafewuncheckedexceptionsintheJCICSAPI,andtheyallextendtheCICSruntimeexceptionclass.

AlloftheseexceptionsrepresentconditionswithinCICSthatshouldnotbehandledbyanapplication.

JavacoderunninginCICSshouldnotcatchtheseexceptions,eitherexplicitlyinacatchblock,orimplicitlybycatchingasuperclassoftheseexceptions.Instead,theyshouldbeallowedtopropagateoutoftheJavaenvironmentandbacktoCICS,wheretheunitofworkcanberolledback.

NoteincludedinthislististheAbendExceptionwhichrepresentsanabendofaCICStask,andshouldonlybecaughtifyouwishtodevelopyourownabendhandlingroutine.

ItimportanttostressthathavingatryblockthatcatchesanysuperclassofthejavadotlangdotexceptionclassshouldnotbeusedwheninvokingtheJCICSAPI.

ItimportanttostressthathavingatryblockthatcatchesanysuperclassofthejavadotlangdotexceptionclassshouldnotbeusedwheninvokingtheJCICSAPI.

<<Notetovideoteam.Youwillprobablyneedtopausethespeakerhereforashortwhile–thecomplexityofthisslidewasn’treallythoughtaboutwhenpreparingthescript.ThankfullyIamoff-screen.>>

TheJavaErrorclassrepresentsafatalerrorconditionintheJVMthatshouldnotbecaughtbyanapplication.

ThesameappliestotheCICSerrorclass,whichextendsjavadotlangdoterror.AnapplicationshouldnotattempttohandleafatalCICSerror,butinsteadallowtheexceptiontopropagatebacktotheCICSenvironmenttoallowfullrecoverytotakeplace.

IfaJavaexceptionsuchasanullpointerexceptionisallowedtopropagateoutoftheJavacodeandbacktotheJVMserverruntime,thisisgenerallysurfacedasoneoftheCICSabendsstartingwithAJ.

Mostcommonly,anuncaughtexceptionwillresultinanAJ04abend,andthecurrentunitofworkwillberolled-back.

ItisalsopossibleforaJavaapplicationtoissueanabenddirectly,usingoneoftheabendorforceabendmethodsintheTaskclass.ThisissimilarinconcepttothethrowingofJavaexception,asitcanallowsaCICSabendhandlertotakecontroloferrorprocessing.

Thevariousformsoftheabendmethodallowanapplicationtooptionallyspecifyanabendcodeorifadumpisrequired.

Theforceabendmethodsprovidethesameoptionsastheirequivalentabendmethods,butareequivalenttospecifyingtheCANCELkeywordontheEXECCICSABENDcommand.Invokingaforce

abendmethodwillalwaysterminatethetaskabnormally,andoverridesanyexistingabendhandlersthathavebeenestablishedforthetask.

InoursampleVsamKsdsFileResourceclassweusethefollowingtrycatchblocktohandleCICSerrorconditionswhendeletingitemsfromaVSAMfile

TheRecordNotFoundExceptionisacheckedexceptionbutisanormalsituationontheinitialbrowse,assocanbeignoredwhenbrowsingthefile.

AllotherCICSconditionexceptionareunexpected,andinthissituationwethrowtheJAX-RSInternalServerErrorExceptionwhichwillcauseaHTTPservererrortobereturnedtothecaller.

ThislecturehasintroducedtheconceptofcheckedanduncheckedexceptionsinJava,alongwiththethrowingandcatchingmechanismusedtopropagatetheexceptionobjects.

WehaveseenhowtheJCICSAPImapsCICSerrorconditionvaluestoexceptions,andhowCICSabendsareprocessed.

RememberitisacceptableforanapplicationtocatchandhandleCICSconditionexceptions,butitstronglyrecommendedthatCICSruntimeexceptionsareallowedtopropagatebacktotheCICSenvironment.

Finally,welookedathowJavaexceptionsaremappedtoabendsinCICSprograms,alongwiththeAPIsrequiredtoissueabendsdirectlyfromJavacode.

Thankyouforwatching.

Section6Lecture1

Inthiscourse,wehaveextendedourknowledgeofJavadevelopmentinCICS.

WecoveredsomeofthefundamentalconceptsyouneedtounderstandasaJavadeveloperwheninteractingwithCICS,andthenusedthesefundamentalstoinvokeCICSprogramsfromtheLibertyenvironment.

WethenlookedattheuseoftheJCICSAPItoaccessCICSresourcesincludingVSAMfilesandTSQs,andexaminedhowJavaapplicationscanparticipateinCICSunitofworksupport.

Finally,welookedattheconceptsandpracticalitiesofhandlingerrorconditionsusingJava.

Manycodesamples,includingtheonesusedinthiscourse,areavailableonourCICSDevgithubsite.

ThisconcludesourcoursearoundextendingaCICSwebapplicationusingJCICS.

Thank-youforwatching.