Les associations entre entités avec JPA

Contrôles des relations entre entités avec JPA.

Lecture
Containers
Java
JPA
Persistence
ORM
Apprenez à gérer les associations entre entités en utilisant Jakarta Persistence API (JPA) avec des exemples pratiques en Java.
Auteur
Affiliations

Emmanuel BRUNO

Université de Toulon

LIS UMR CNRS 7020

Date de publication

2026-10-01

JPA offre une prise en charge complète pour la gestion des relations entre entités de différents types, que ce soit en mode un-vers-un (OneToOne), un-vers-plusieurs (OneToMany), ou plusieurs-vers-plusieurs (ManyToMany). Ces relations peuvent être configurées de manière unidirectionnelle ou bidirectionnelle.

One To One (1-1)

Dans certaines situations, lors de la modélisation orientée objet, il est nécessaire d’associer deux classes dans une relation un-à-un, mais en gardant une seule relation.

java.io.IOException: Cannot run program "/opt/local/bin/dot": Exec failed, error: 2 (No such file or directory) 
    at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1112)
    at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1046)
    at net.sourceforge.plantuml.dot.ProcessRunner.run(ProcessRunner.java:71)
    at net.sourceforge.plantuml.dot.ProcessRunner.run(ProcessRunner.java:60)
    at net.sourceforge.plantuml.dot.GraphvizVersionFinder.dotVersion(GraphvizVersionFinder.java:120)
    at net.sourceforge.plantuml.dot.GraphvizVersionFinder.getVersion(GraphvizVersionFinder.java:75)
    at net.sourceforge.plantuml.dot.GraphvizRuntimeEnvironment.getVersion(GraphvizRuntimeEnvironment.java:86)
    at net.sourceforge.plantuml.svek.DotStringFactory.getGraphvizVersionInternal(DotStringFactory.java:278)
    at net.sourceforge.plantuml.svek.DotStringFactory.getGraphvizVersion(DotStringFactory.java:267)
    at net.sourceforge.plantuml.svek.GraphvizImageBuilder.printEntityInternal(GraphvizImageBuilder.java:381)
    at net.sourceforge.plantuml.svek.GraphvizImageBuilder.printEntity(GraphvizImageBuilder.java:363)
    at net.sourceforge.plantuml.svek.GraphvizImageBuilder.printEntities(GraphvizImageBuilder.java:355)
    at net.sourceforge.plantuml.svek.GraphvizImageBuilder.buildImage(GraphvizImageBuilder.java:225)
    at net.sourceforge.plantuml.svek.CucaDiagramFileMakerSvek.createFileInternal(CucaDiagramFileMakerSvek.java:104)
    at net.sourceforge.plantuml.svek.CucaDiagramFileMakerSvek.createFile(CucaDiagramFileMakerSvek.java:70)
    at net.atmp.CucaDiagram.exportDiagramInternal(CucaDiagram.java:489)
    at net.sourceforge.plantuml.classdiagram.ClassDiagram.exportDiagramInternal(ClassDiagram.java:85)
    at net.sourceforge.plantuml.UmlDiagram.exportDiagramNow(UmlDiagram.java:119)
    at net.sourceforge.plantuml.AbstractPSystem.exportDiagram(AbstractPSystem.java:216)
    at net.sourceforge.plantuml.SourceStringReader.outputImage(SourceStringReader.java:189)
    at net.sourceforge.plantuml.SourceStringReader.outputImage(SourceStringReader.java:147)
    at io.github.spencerpark.ijava.magics.JavaPlantUMLMagics.plantUML(JavaPlantUMLMagics.java:53)
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
    at java.base/java.lang.reflect.Method.invoke(Method.java:565)
    at io.github.spencerpark.jupyter.kernel.magic.registry.Magics.invoke(Magics.java:89)
    at io.github.spencerpark.jupyter.kernel.magic.registry.Magics$CellReflectionMagicFunction.execute(Magics.java:164)
    at io.github.spencerpark.jupyter.kernel.magic.registry.Magics.applyCellMagic(Magics.java:36)
    at REPL.$JShell$61.do_it$($JShell$61.java:65)
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
    at java.base/java.lang.reflect.Method.invoke(Method.java:565)
    at io.github.spencerpark.ijava.execution.IJavaExecutionControl.lambda$execute$0(IJavaExecutionControl.java:95)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:328)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1090)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:614)
    at java.base/java.lang.Thread.run(Thread.java:1474)
Caused by: java.io.IOException: Exec failed, error: 2 (No such file or directory) 
    at java.base/java.lang.ProcessImpl.forkAndExec(Native Method)
    at java.base/java.lang.ProcessImpl.<init>(ProcessImpl.java:300)
    at java.base/java.lang.ProcessImpl.start(ProcessImpl.java:231)
    at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1078)
    ... 34 more
Figure 1: Un Customer a une Biography 
No JDBC connection available. Set system properties 'jdbc.url' (and optionally 'jdbc.user'/'jdbc.password'), or provide a Connection in the kernel environment.
Figure 2

Pour cela JPA propose des annotations spécifiques :

@Embeddable: Cette annotation indique que les membres d’une classe Java peuvent être persistés en tant qu’attributs de la classe qui les utilise. En d’autres termes, elle spécifie qu’une classe peut être utilisée comme composant réutilisable dont les propriétés peuvent être incorporées dans une autre entité.

@Embedded: Utilisée au niveau d’un membre de classe annoté avec @Embeddable, cette annotation indique que le membre annoté doit être intégré dans la relation. Cela signifie que les propriétés de la classe annotée avec @Embeddable seront incluses dans la table de la classe qui les utilise.

@Builder
@NoArgsConstructor(access = AccessLevel.PROTECTED)
@AllArgsConstructor

@Embeddable
public class Biography {
    @Column(name = "BIO_BRIEF")
    private String brief;

    @Lob
    @Column(name = "BIO_EXTENDED")
    private String extended;
}
Figure 3: Embeddable.java 
@Getter
@Setter
@ToString
@RequiredArgsConstructor(staticName = "of")
@NoArgsConstructor(access = AccessLevel.PROTECTED)

@Entity
@Table(name = "CUSTOMER", schema = "ex_biography")
public class Customer {
    @Id
    @GeneratedValue
    private long id;

    @Column(length = 50, nullable = false)
    @NonNull
    private String name;

    @Embedded
    @Column()
    private Biography biography;
}

Customer.java

On peut donc rendre persistente une instance de Customer associé à une instance de Biography.

Creation et persistence d’un Customer 
import fr.univtln.bruno.demos.jpa.hello.samples.ex_biography.Customer;
try (EntityManager entityManager = emf.createEntityManager()) {
   entityManager.getTransaction().begin();

   Customer customer = Customer.of("Jim");
   customer.setBiography(Biography.builder()
      .brief("bla")
      .extended("bla bla")
      .build());
   entityManager.persist(customer);

   entityManager.getTransaction().commit();
}

dans une seule relation

No JDBC connection available. Set system properties 'jdbc.url' (and optionally 'jdbc.user'/'jdbc.password'), or provide a Connection in the kernel environment.
Figure 4

One to Many (1-N)

Figure 5: Une Order a plusieurs Line 
@Getter
@Setter
@ToString
@AllArgsConstructor(staticName = "of")
@NoArgsConstructor(access = AccessLevel.PROTECTED)

@Embeddable
@Table(name = "LINE", schema = "EX_ONE_TO_MANY_B")
public class Line {
    @NonNull
    private String product;

    private double price;
}
@Getter
@Setter
@ToString
@NoArgsConstructor
@Builder
@AllArgsConstructor

@Entity
@Table(name = "EORDER", schema = "EX_ONE_TO_MANY_B")
public class Order {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private long id;

    @Builder.Default
    @Column(nullable = false)
    private LocalDateTime date = LocalDateTime.now();

    @ElementCollection
    @CollectionTable(name = "LINE", schema = "EX_ONE_TO_MANY_B")
    @Singular
    private Set<Line> lines = new HashSet<>();

}
No JDBC connection available. Set system properties 'jdbc.url' (and optionally 'jdbc.user'/'jdbc.password'), or provide a Connection in the kernel environment.
Figure 6

Avec deux entités

Dans le cas général, l’attribut de type Collection<T> est annoté avec @OneToMany.

L’attribut optionnel mappedBy indique le nom de l’attribut correspondant dans le type T si l’on souhaite une relation bi-directionnelle. L’autre entité (de Type T) est alors annotée avace @ManyToOne

@Getter
@Setter
@ToString
@NoArgsConstructor

@Entity
@Table(name = "EORDER", schema = "EX_ONE_TO_MANY_A")
public class Order {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private long id;

    private LocalDateTime date = LocalDateTime.now();

    @OneToMany(mappedBy = "order",
            cascade = {CascadeType.PERSIST,
                    CascadeType.REMOVE},
            orphanRemoval = true)
    @ToString.Exclude
    private Set<Line> lines = new HashSet<>();

    public Order addLine(Line line) {
        line.setOrder(this);
        lines.add(line);
        return this;
    }

    public Order removeLine(Line line) {
        line.setOrder(null);
        lines.remove(line);
        return this;
    }
}
@Getter
@Setter
@ToString
@RequiredArgsConstructor(staticName = "of")
@NoArgsConstructor(access = AccessLevel.PROTECTED)

@Entity
@Table(name = "LINE", schema = "EX_ONE_TO_MANY_A")
public class Line {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private long id;
    @NonNull
    private String product;

    @NonNull // just for requiredargsconstructor
    private double price;

    @ManyToOne
    @JoinColumn(nullable = false)
    @ToString.Exclude
    private Order order;

    public void setOrder(Order order) {
        if (this.order != null) {
            this.order.getLines().remove(this);
        }
        this.order = order;
        if (order != null) {
            order.getLines().add(this);
        }
    }
}
12:25:16.807 [IJava-executor-0] INFO  notebook -- Order(id=1, date=2026-10-01T12:25:16.666150) [Line(id=1, product=Paper, price=5.0), Line(id=3, product=Scissor, price=8.0), Line(id=2, product=Pen, price=1.0)]
No JDBC connection available. Set system properties 'jdbc.url' (and optionally 'jdbc.user'/'jdbc.password'), or provide a Connection in the kernel environment.
Figure 7 
No JDBC connection available. Set system properties 'jdbc.url' (and optionally 'jdbc.user'/'jdbc.password'), or provide a Connection in the kernel environment.
Figure 8

Many to Many (N-M)

L’annotation @ManyToMany en Java Persistence API (JPA) est utilisée pour modéliser une relation many-to-many entre deux entités. La table d’association sera alors générée et utilisée implicitement.

Figure 9: Un Customer a plusieurs adresses (qui peuvent être associées à d’autres) 
No JDBC connection available. Set system properties 'jdbc.url' (and optionally 'jdbc.user'/'jdbc.password'), or provide a Connection in the kernel environment.
Figure 10 
@Getter
@Setter
@ToString
@RequiredArgsConstructor(staticName = "of")
@NoArgsConstructor(access = AccessLevel.PROTECTED)

@Entity
@Table(name = "CUSTOMER", schema = "EX_MANY_TO_MANY")
public class Customer {
    @Id
    @GeneratedValue
    private long id;

    @NonNull
    private String name;

    @ManyToMany
    @ToString.Exclude
    @JoinTable(schema = "EX_MANY_TO_MANY")
    private Set<Address> places = new HashSet<>();

    public void addPlace(Address address) {
        this.places.add(address);
        address.getOccupants().add(this);
    }

    public void removePlace(Address address) {
        this.places.remove(address);
        address.getOccupants().remove(this);
    }
}
@Getter
@Setter
@ToString
@RequiredArgsConstructor(staticName = "of")
@NoArgsConstructor(access = AccessLevel.PROTECTED)

@Entity
@Table(name = "ADDRESS", schema = "EX_MANY_TO_MANY")
public class Address {
    @Id
    @GeneratedValue
    private long id;

    @NonNull
    private String addressDetail;

    @ManyToMany(mappedBy = "places")
    @ToString.Exclude
    private Set<Customer> occupants= new HashSet<>();

    public void addOccupant(Customer customer) {
        this.occupants.add(customer);
        customer.getPlaces().add(this);
    }

    public void removeOccupant(Customer customer) {
        this.occupants.remove(customer);
        customer.getPlaces().remove(this);
    }

}
No JDBC connection available. Set system properties 'jdbc.url' (and optionally 'jdbc.user'/'jdbc.password'), or provide a Connection in the kernel environment.
Figure 11 
No JDBC connection available. Set system properties 'jdbc.url' (and optionally 'jdbc.user'/'jdbc.password'), or provide a Connection in the kernel environment.
Figure 12 
No JDBC connection available. Set system properties 'jdbc.url' (and optionally 'jdbc.user'/'jdbc.password'), or provide a Connection in the kernel environment.
Figure 13

Réutilisation