Type-safe Functional Queries over Object-oriented Data Models

75 Pages·2009·0.99 MB·English

Type-safe Functional Queries over
Object-oriented Data Models
DiplomThesis
submittedby
KhaledAlshurafa
supervisedby
Prof. Dr. RalfMöller
Prof. Dr. DieterGollmann
HamburgUniversityofScienceandTechnology
SoftwareSystemsInstitute(STS)
July30,2009
Abstract
UtilizingtheJavaPersistenceAPI(JPA)anditsquerylanguageJavaPersistenceQueryLan-
guage (JPQL), developers can easily interact with relational data structures from the object
level. JPQLisovershadowedhoweverwiththelackofpropertype-safeandfunctionalcapa-
bilities. Unlikeitscounterpartonthe.NETframework,LanguageINtegratedQuery(LINQ).
This work discusses, on the one hand, possibilities of translating LINQ into JPQL, and the
impact of the newer JPA on the research done so far, and on the other hand, processing of
queryresultsassecondary-memoryobjectsthatarejoinedwithotheronesoperatingonthe
main-memory. Largedatasetscannotbehandledadequatelyinmain-memory,andafflicted
with mapping and memory-architecture constraints when moving from one memory to an-
other. Simpleiterationtechniquesinimperativelanguagesleadtypicallytoineffectivenested
loops. Tothecontraryoffunctionallanguages,listcomprehensionsareoftendeployedthere
tohandledatasetssuccinctlyanddynamically. Comprehensionsarereinforcedbyaproper
semanticfoundation.
Declaration
Ideclarethat:
thisworkhasbeenpreparedbymyself,
allliteralorcontentbasedquotationsareclearlypointedout,
andnoothersourcesoraidsthanthedeclaredoneshavebeenused.
Hamburg,July30,2009
KhaledAlshurafa
I owe special gratitude to Prof. Dr. Möller for providing me with valuable insights
andpracticalguidance,aswellasencouragementthroughouttheresearch.
Iwouldliketothankmyfamilyfortheirunwaveringsupport, andmywifeandbest
friendBerrinforbelievinginme.
Contents
ListofFigures v
ListofTables vi
Listings vii
ListofAcronyms viii
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 ProblemDescription . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 TaskDescription . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 RelatedWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.5 OrganizationoftheReport . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 LINQandJPAQueryingCapabilities 6
2.1 LanguageINtegratedQuery(LINQ) . . . . . . . . . . . . . . . . . . . . . . 6
2.1.1 DistinctiveFeatures. . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.2 ORMinLINQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.3 Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2 JavaPersistenceAPI(JPA) . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.1 SettingtheORM . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2 JPQLinAction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.3 JPA2.0andCriteriaAPI . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3 Type-safeQueryProcessing 16
3.1 DesignAspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.1.1 CompileTimeChecks . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.1.2 FunctionalQualities . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.1.3 MechanicalNotes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.1.4 MoreonTranslatingLINQtoJPQL . . . . . . . . . . . . . . . . . . 19
3.1.5 MoreonJPA2.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2 LanguageImplementations . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2.1 Quaere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.2.2 JaQue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
iii
4 ManipulatingObjectPopulations 25
4.1 ProcessingofQueryResult . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.1.1 IterationoverResultObjects . . . . . . . . . . . . . . . . . . . . . . 25
4.1.2 HierarchicalStructures . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.2 ObjectsResidinginDifferentMemories . . . . . . . . . . . . . . . . . . . . 29
4.2.1 Secondary-memoryObjects . . . . . . . . . . . . . . . . . . . . . . 29
4.2.2 MethodCallsonORM-mappedObjects . . . . . . . . . . . . . . . . 30
4.2.3 Memory-relatedRestrictions . . . . . . . . . . . . . . . . . . . . . . 30
4.3 OperationsonObjects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.3.1 MethodsforComputingJoins . . . . . . . . . . . . . . . . . . . . . 33
4.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5 FunctionalComputingwithListComprehensions 36
5.1 FunctionalNestedLoops . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.1.1 ExpressingLoopsasListComprehensions . . . . . . . . . . . . . . 36
5.1.2 Higher-orderFunctionsandListComprehensions . . . . . . . . . . . 37
5.1.3 LoopsinSelectedFunctionalLanguagesfromanImperativePerspec-
tive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5.2 ImplementationsofEffectiveIterationTechniques . . . . . . . . . . . . . . . 39
5.2.1 Higher-orderFunctionsandClosures . . . . . . . . . . . . . . . . . 39
5.2.2 ListComprehensions . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.3 DenotationalSemanticsforLoopStructures . . . . . . . . . . . . . . . . . . 43
5.3.1 MonoidComprehensionCalculusandAlgebra . . . . . . . . . . . . 43
5.3.2 TheNeedofDenotationalSemantics . . . . . . . . . . . . . . . . . 47
5.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
6 ConclusionandFutureWork 49
6.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
6.2 FutureWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
A ProjectConfigurationPreferences 53
A.1 PreparingtheJPAProject . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
A.2 SettingtheJPAProject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
B SourceCodeforTestingPurposes 55
B.1 UsingQuaere,JaQue,andKijaro . . . . . . . . . . . . . . . . . . . . . . . . 55
B.2 Self-ImpliedSimpleListComprehensionsUsingAnonymousJavaClasses. . 57
C MonoidComprehensionCalculusandAlgebra 61
Bibliography 62
Index 65
List of Figures
2.1 LINQanditsenvironment . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Anin-depthlookattheconceptsofJPA . . . . . . . . . . . . . . . . . . . . 10
2.3 Theemployeessampledatabase . . . . . . . . . . . . . . . . . . . . . . . . 11
2.4 PersistentobjectviewofanexistingRDBtable . . . . . . . . . . . . . . . . 12
3.1 Querytranslation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.2 Formulatingqueriesasclosures. . . . . . . . . . . . . . . . . . . . . . . . . 22
4.1 Operationsbetweenobjectsresidingindifferentmemories . . . . . . . . . . 29
4.2 Memoryhierarchy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4.3 Dataaccessbycomparison . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.4 Groupingasasolutionfornestedloops . . . . . . . . . . . . . . . . . . . . 34
v
List of Tables
5.1 Examplesofcollectionandprimitivemonoids . . . . . . . . . . . . . . . . . 43
5.2 Examplesofmonoidcomprehensions . . . . . . . . . . . . . . . . . . . . . 45
C.1 Themainformsofmonoidcomprehensioncalculus . . . . . . . . . . . . . . 61
C.2 Monoidalgebra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
vi
Listings
A.1 Thepersistence.xmlfile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
B.1 QuerieswithQuaere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
B.2 QuerieswithJaQue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
B.3 QuerieswithlistcomprehensionsundertheKijaroproject. . . . . . . . . . . 57
B.4 InterfaceComprehendforprocessinglistcomprehensions . . . . . . . . . . . 57
B.5 ClassComprehendInsforimplementingtheinterfaceComprehend . . . . . . 57
B.6 ClassComprehendUtilforlistprocessing . . . . . . . . . . . . . . . . . . . 58
B.7 Themainclasstodemonstrateprocessingusinglistcomprehensions . . . . . 59
vii
List of Acronyms
API ApplicationProgrammingInterface
AST AbstractSyntaxTree
BNF Backus-NaurForm
DBMS DatabaseManagementSystem
DSL DomainSpecificLanguage
EJB EnterpriseJavaBean
EMF EclipseModelingFramework
IDE IntegratedDevelopmentEnvironment
J2EE Java2Platform,EnterpriseEdition
J2SE Java2Platform,StandardEdition
JAXB JavaArchitectureforXMLBinding
JDBC JavaDatabaseConnectivity
JDK JavaDevelopmentKit
JPA JavaPersistenceAPI
JPQL JavaPersistenceQueryLanguage
JSR JavaSpecificationRequest
JVM JavaVirtualMachine
LINQ LanguageINtegratedQuery
OCL ObjectConstraintLanguage
OODBMS Object-OrientedDatabaseManagementSystem
OQL ObjectQueryLanguage
ORM Object-RelationalMapping
RDB RelationalDatabase
RDBMS RelationalDatabaseManagementSystem
SQO StandardQueryOperators
viii