hibernate.hbm2ddl.auto=update don't work

Question

I have model. there is this part:

model was mapped by jpa annotations.Everywhere I use fetchType = EAGER. If I load vacancy from database, I have 2 duplicates status_for_vacancy objects. I use property hbm2ddl.auto = update. If I make new schema of database and fill data, I haven't duplicates status_for_vacancy objects. It really?

code: vacancy:

@Entity
@Table(name = "vacancy")
@XmlRootElement(name="vacancy")

public class Vacancy {

    private List<VacancyStatus> statusList = new LinkedList<VacancyStatus>();

    @OneToMany(mappedBy = "vacancy", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    public List<VacancyStatus> getStatusList() {
        return statusList;
    }

    public void setStatusList(List<VacancyStatus> statusList) {
        this.statusList = statusList;
    }

}

status_for_vacancy:

@Entity
@Table(name = "status_for_vacancy")
public class StatusForVacancy extends AbstractStatus {

    public StatusForVacancy() {
        super();
    }

    public StatusForVacancy(Integer id, String name) {
        super(id, name);
    }

}


@MappedSuperclass
@XmlRootElement
public abstract class AbstractStatus {

    private Integer id;
    private String name;

    public AbstractStatus() {
        super();
    }

    public AbstractStatus(String name) {
        super();
        this.name = name;
    }

    public AbstractStatus(Integer id, String name) {
        super();
        this.id = id;
        this.name = name;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column (name ="id")
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    @Column(name = "name")
    @NotEmpty
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

vacancy_status:

@Entity
@Table(name = "vacancy_status")
public class VacancyStatus extends AbstractHistoryStatus {

    private Vacancy vacancy;
    private StatusForVacancy status;

    public VacancyStatus() {
        super();
    }

    public VacancyStatus(Integer id, User author, Date date, 
            Vacancy vacancy, StatusForVacancy status) {
        super(id, author, date);
        this.vacancy = vacancy;
        this.status = status;
    }


    @ManyToOne
    @JoinColumn(name = "vacancy_id")
    public Vacancy getVacancy() {
        return vacancy;
    }

    public void setVacancy(Vacancy vacancy) {
        this.vacancy = vacancy;
    }

    @ManyToOne
    @JoinColumn(name = "status_id")
    public StatusForVacancy getStatus() {
        return status;
    }

    public void setStatus(StatusForVacancy status) {
        this.status = status;
    }
}


@MappedSuperclass
public abstract class AbstractHistoryStatus {

    private Integer id;
    private User author;
    private Date date;


    public AbstractHistoryStatus() {
    }

    public AbstractHistoryStatus(Integer id, User author, Date date) {
        super();
        this.id = id;
        this.author = author;
        this.date = date;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    @ManyToOne
    public User getAuthor() {
        return author;
    }

    public void setAuthor(User author) {
        this.author = author;
    }

    @Column(name="creation_date")
    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

}

It is all mapping code for these entities.

in debugger:

both id==500 ==> hibernate understand, that it is same objects.

I try add all data from old database to new database - I get old error(

I fix cause of appearance of this problem. It appearances if I add record to note table:

Answer 1

I highly recommend you write equals() and hashCode() methods. The standard equals()/hashCode() implement referential equality (do 2 objects reference the same memory location). So if hibernate has 2 of the 'same' object in memory, but they don't reference the same memory location then you will see the object show up twice. But if you implement equals() based on primary key being equal, then even if there are two copies of the same object in memory, Hibernate won't give you duplicates.

See the JPA spec:

2.4 Primary Keys and Entity Identity

Every entity must have a primary key. ... The value of its primary key uniquely identifies an entity instance within a persistence context and to EntityManager operations

Also see this SO post.