I have a UserEntity that has a @ManyToMany bidirectional mapping association with ConversationEntity. The issue I’m facing is when I save a detached UserEntity that has an empty conversation mapping (even though there are associated conversations in the database), I expect that the entity will be merged and the @ManyToMany mapping will be populated in the returned entity. However, the associations are not being populated in the returned entity after the merge operation.

what is happening here, am I doing something wrong ?

@Transactional
public UserEntity saveUser(UserModel userModel) {
    log.debug("Saving user {}", userModel);
    
    // Converting UserModel to UserEntity (this creates a detached entity)
    UserEntity userEntity = UserEntity.from(userModel);
    
    log.debug("Converted User Entity {}", userEntity);
    
    // Merging the detached entity
    userEntity = userRepository.saveAndFlush(userEntity);
    
    // Refreshing the entity as a workaround
    //entityManager.refresh(userEntity);
    
    log.debug("Conversations : {}", userEntity.getConversations());
    
    return UserEntity.toModel(userEntity);
}

@Entity
public class UserEntity {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @ManyToMany(fetch = FetchType.EAGER, mappedBy = "members", cascade = {CascadeType.MERGE, CascadeType.REFRESH})
    @Builder.Default
    private Set<ConversationEntity> conversations = new HashSet<>();
    
    // Other fields and methods
}

@Entity
public class ConversationEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToMany(fetch = FetchType.LAZY)
    @JoinTable(name = "conversation_user",
            joinColumns =
            @JoinColumn(name = "conversation_id" , referencedColumnName = "id"),
            inverseJoinColumns =
            @JoinColumn(name = "user_id",referencedColumnName = "id") )
    
    private Set<UserEntity> members = new HashSet<>();

    // Other fields and methods
}

I have tried with modifying LAZY loading to EAGER , with no luck