How to manage OnetoOne inserting data in child only

Question

I am very new to hibernate and I am working with JPA and Hibernate4. Trying to insert parent object in child as onetoone relationship.

I went through some tutorials but All the example in the web shows, inserting both parent and child tables.

I want to insert data in child table only.

I have two tables called user and department.

User table consists of user details with department as onetoone relationship, as follows,

@Entity
@Table(name = "User")
public class UserEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "_id")
    private String id;

    @Column(name = "firstName")
    private String firstName;

    @Column(name = "lastName")
    private String lastName;

    @OneToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "departmentId")
    private Department departmentId;

    // getters and setters...

}

Below is my Department entity,

@Entity
@Table(name = "Department")
public class Department {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "_id")
    private String id;

    @Column(name = "name")
    private String name;

    // getters and setters...
}

In department table there is only 4 data. I want to insert data only in user data while insert into it and don't want to insert in Department.

How can I do that.Please assist.

Answer 1

You have to use mappedBy for this, as mentoned below in child Table, Department in your case

@OneToOne(mappedBy="department")
private UserEntity user;

These posts explain you better this,

JPA JoinColumn vs mappedBy

Understanding mappedBy annotation in Hibernate