Persist Nested Entity Spring Rest Data

Question

I have a User Class

@Entity(name = "users")
@Table(name = "users")
public class User implements UserDetails {

static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "user_id", nullable = false)
private Long id;

@Column(name = "username", nullable = false, unique = true)
private String username;

@Column(name = "password", nullable = false)
private String password;
}

Tied to a simple Repository

public interface UserRepository extends PagingAndSortingRepository<User, Long> {
}

And I have an Instructor Class that has a nested User object

@Entity
@Table(name = "instructors")
public class Instructor {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "instructor_id", nullable = false, updatable = false)
private Long id;

@OneToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "user_id")
private User user;

@OneToMany(fetch = FetchType.EAGER)
@JoinColumn(name = "course_id")
private List<Course> courses;

}

It is saved with the following repository

public interface InstructorRepository extends PagingAndSortingRepository<Instructor, Long> {

}

The JSON I am posting

{
"user": {
    "id": 1
}
}

When I try to do a POST to /instructors . User is coming in null. Is there something I am missing to get JPA to tie the two together? I have tried adding CascadeType.ALL onto the field and that only throws a detached persist exception.

Answer 1

Leave the CascadeType.ALL to Instructor like you already tried:

@ManyToOne(fetch = FetchType.EAGER, cascade=CascadeType.ALL)
@JoinColumn(name = "user_id")
private User user;

In addition add the following to User . Seems to work with me. It provides the mapping information and makes JPA treat User managed

@OneToMany(mappedBy="user")//, cascade=CascadeType.ALL)
private List<Instructor> instructors = new ArrayList<>();

I have commented out the cascadeType in the above but it might be useful if you want to persist User wit all of its Instructors .