[FIXED] Hibernate One to One mapping Foreign Key null

Issue

Here I m having two different tables, User and Profile Image. Both are mapped using One to One relation. The problem is- Foreign key of Profile Image (user_userid) is null when a new profile image is inserted into the database. Why is the user_id remains null... I come up with this issue many time.... Is there any issue with the way I m mapping both the entities?...

User

@Entity
@Getter
@Setter
@Table(name = "Users")
public class User {

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

    @OneToOne(cascade = CascadeType.ALL,mappedBy = "user",fetch =FetchType.LAZY)
    private UserProfileImage userProfileImage;
}

Profile Image

@Entity
@Getter
@Setter
public class UserProfileImage {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    @Column(name = "name")
    private String name;
    @Column(name = "type")
    private String type;
    @Column(name = "picByte", length = 1000000)
    private byte[] picByte;

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

    public UserProfileImage() {
        super();
    }

    public UserProfileImage(String name, String type, byte[] picByte) {
        this.name = name;
        this.type = type;
        this.picByte = picByte;
    }
}

Controller

public ResponseEntity<String> addProfileImage(int id,MultipartFile file) {
        User user=userRepository.findById(id);
        UserProfileImage present=user.getUserProfileImage();
        if(present==null) {
            UserProfileImage userProfileImage = new UserProfileImage(file.getOriginalFilename(), file.getContentType(), file.getBytes());
            user.setUserProfileImage(userProfileImage);
        }else{
            present.setName(file.getOriginalFilename());
            present.setType(file.getContentType());
            present.setPicByte(file.getBytes());
            user.setUserProfileImage(present);
        }
        userRepository.save(user);
       
    }

Solution

As it's stated in the hibernate documentation:

Whenever a bidirectional association is formed, the application developer must make sure both sides are in-sync at all times.

So, you should correct your addProfileImage method in this way:

public ResponseEntity<String> addProfileImage(int id,MultipartFile file) {
  User user=userRepository.findById(id);
  UserProfileImage present=user.getUserProfileImage();
  if(present==null) {
     UserProfileImage userProfileImage = new UserProfileImage(file.getOriginalFilename(), file.getContentType(), file.getBytes());

     // sync both sides of bidirectional association
     user.setUserProfileImage(userProfileImage);
     userProfileImage.setUser(user);
  } else {
      present.setName(file.getOriginalFilename());
      present.setType(file.getContentType());
      present.setPicByte(file.getBytes());

      // this is redundant
      // user.setUserProfileImage(present);
  }
  userRepository.save(user);
}

Answered By - SternK
Answer Checked By - Mary Flores (JavaFixing Volunteer)