Question

我正在尝试一些JPA + Hibernate配置，我遇到了单向ManyToMany的问题。我的测试应用程序正在为Person和Event建模;该活动有一个创作者，但有很多参与者

这是我的活动：

@Entity
@Table(name = "EUO")
public class EventUnidirectionalRelationshipOwner {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String title;

    @Temporal(TemporalType.DATE)
    private Date eventDate;

    @ManyToOne(cascade = CascadeType.PERSIST)
    private PersonUnidirectionalNonRelationshipOwner creator;

    @ManyToMany(cascade = {CascadeType.PERSIST})
    @JoinTable(name = "participant_event_U")
    private Set<PersonUnidirectionalNonRelationshipOwner> participants;

    protected EventUnidirectionalRelationshipOwner() {
        super();
    }

    public EventUnidirectionalRelationshipOwner(String title, Date eventDate,
            PersonUnidirectionalNonRelationshipOwner creator) {
        this.title = title;
        this.eventDate = eventDate;
        this.creator = creator;
        this.participants = new HashSet<>();
    }

    /* get and set */

    public void registerParticipant(PersonUnidirectionalNonRelationshipOwner participant) {
        participants.add(participant);
    }
}

人：

@Entity
@Table(name = "PUN", uniqueConstraints = @UniqueConstraint(name = "key_fNlNS", columnNames = {
        "firstName", "lastName", "ssn" }))
public class PersonUnidirectionalNonRelationshipOwner {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String firstName;
    private String lastName;
    private String ssn;

    /*
     * required by Hibernate. Protected because not meaningful for the
     * application (no default values for title and eventDate)
     */
    protected PersonUnidirectionalNonRelationshipOwner() {
        super();
    }

    public PersonUnidirectionalNonRelationshipOwner(String firstName,
            String lastName, String ssn) {
        super();
        this.firstName = firstName;
        this.lastName = lastName;
        this.ssn = ssn;
    }
    /* get and set */
}

测试主要：

// CASE 1
PersonUnidirectionalNonRelationshipOwner p1 = new PersonUnidirectionalNonRelationshipOwner(
                "p1n", "p1l", "ssn1");
EventUnidirectionalRelationshipOwner e1 = new EventUnidirectionalRelationshipOwner(
                "e1", new Date(), p1);
PersonUnidirectionalNonRelationshipOwner pp1 = new PersonUnidirectionalNonRelationshipOwner(
                "pp1n", "pp1l", "pssn1");
e1.registerParticipant(pp1);

EventDaoJPA.store(e1);

最后是商店方法：

EntityManager em = DBResourcesManager.getEntityManager();
em.getTransaction().begin();
em.persist(e);
em.getTransaction().commit();

但是，当我调用store时，不填充连接表，而实体表是。为了填充连接表，我需要在提交事务后调用em.refresh（e）。有没有办法避免这两步程序？

除非在持久提交后调用刷新，否则不会填充单向ManyToMany连接表

0 个答案: