CODEWITHSUNDEEP
javamysqlhibernatejpaorm
Louie
Louie

Reputation: 1

@OneToOne(mappedBy) causes column to not be created

I am trying to learn JPA and Hibernate. When trying to use the mappedBy annotation to map a access card to an owner of it, the column wont create. I am new to stack overflow so forgive me if I am doing this wrong.

Here is my Employee class

@Entity
@Table(name = "EMPLOYEE_DATA")
public class Employee {

    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private int id;
    @Column(name = "EMPLOYEE_NAME")
    private String name;
    @Column(unique = true, length = 9, nullable = false, updatable = false)
    private String ssn;
    @Column(nullable = true)
    private int age;
    @Temporal(TemporalType.DATE)
    private Date dob;
    @Enumerated(EnumType.STRING)
    private EmployeeType type;
    @OneToOne
    private AccessCard card;
    @Transient
    public String debugString;

    //getters and setters, toString

Here is my AccessCard class

@Entity
@Table(name = "ACCESS_CARD")
public class AccessCard {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private int id;
    @Temporal(TemporalType.DATE)
    private Date issueDate;
    private boolean isActive;
    private String firmwareVersion;
    @OneToOne(mappedBy = "card")
    private Employee owner;

   //getters and setters, toString

Here is my JpaStarterMain class used to create the objects and persist them

public class JpaStarterMain {
    public static void main(String[] args) {

        Employee employee2 = new Employee();
        employee2.setType(EmployeeType.FULL_TIME);
        employee2.setAge(24);
        employee2.setDob(new GregorianCalendar(1998, Calendar.OCTOBER, 20).getTime());
        employee2.setName("Louie Jenkins");
        employee2.setSsn("123456789");

        Employee employee1 = new Employee();
        employee1.setType(EmployeeType.PART_TIME);
        employee1.setAge(21);
        employee1.setDob(new GregorianCalendar(2001, Calendar.OCTOBER, 5).getTime());
        employee1.setName("Gigi Vad");
        employee1.setSsn("987654321");

        AccessCard card2 = new AccessCard();
        card2.setFirmwareVersion("2.7.0");
        card2.setIssueDate(new Date());
        card2.setActive(true);
        card2.setOwner(employee2);
        employee2.setCard(card2);

        AccessCard card1 = new AccessCard();
        card1.setFirmwareVersion("2.7.0");
        card1.setIssueDate(new Date());
        card1.setActive(false);
        card1.setOwner(employee1);
        employee1.setCard(card1);

        EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("test");
        EntityManager entityManager = entityManagerFactory.createEntityManager();
        EntityTransaction transaction = entityManager.getTransaction();

        transaction.begin();

        entityManager.persist(employee1);
        entityManager.persist(employee2);
        entityManager.persist(card1);
        entityManager.persist(card2);

        transaction.commit();
        entityManager.close();
        entityManagerFactory.close();

I get this in the console

Hibernate: insert into EMPLOYEE_DATA (age, card_id, dob, EMPLOYEE_NAME, ssn, type, id) values (?, ?, ?, ?, ?, ?, ?)
Hibernate: insert into EMPLOYEE_DATA (age, card_id, dob, EMPLOYEE_NAME, ssn, type, id) values (?, ?, ?, ?, ?, ?, ?)
Hibernate: insert into ACCESS_CARD (firmwareVersion, isActive, issueDate, id) values (?, ?, ?, ?)
Hibernate: insert into ACCESS_CARD (firmwareVersion, isActive, issueDate, id) values (?, ?, ?, ?)

for some reason, when getting rid of the mappedBy in the @OneToOne annotation, owner_id is added into the database under the ACCESS_CARD table, but when using mappedBy, it doesn't work anymore! see below

@Entity
@Table(name = "ACCESS_CARD")
public class AccessCard {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private int id;
    @Temporal(TemporalType.DATE)
    private Date issueDate;
    private boolean isActive;
    private String firmwareVersion;
    @OneToOne
    private Employee owner;

   //getters and setters, toString

Then I get this in the console

Hibernate: insert into EMPLOYEE_DATA (age, card_id, dob, EMPLOYEE_NAME, ssn, type, id) values (?, ?, ?, ?, ?, ?, ?)
Hibernate: insert into EMPLOYEE_DATA (age, card_id, dob, EMPLOYEE_NAME, ssn, type, id) values (?, ?, ?, ?, ?, ?, ?)
Hibernate: insert into ACCESS_CARD (firmwareVersion, isActive, issueDate, owner_id, id) values (?, ?, ?, ?, ?)
Hibernate: insert into ACCESS_CARD (firmwareVersion, isActive, issueDate, owner_id, id) values (?, ?, ?, ?, ?)

any help is appreciate thanks!

Upvotes: 0

Views: 69

Answers (1)

Pierre Demeestere
Pierre Demeestere

Reputation: 406

When you use mappedBy, it means that the relation is persisted on the other side of the relation. This is sufficient in terms of data persistence. You can find the same behaviour with a OneToMany relation where the mappedBy attribute gives the name of the corresponding member on the other class annotated with ManytoOne. In this second case, it is more obvious that the persistence is on the manyToOneside.

Upvotes: 1

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