title: JPA Foreign Key Not being Set in @OneToOne
body: <p>I have a @OneToOne relationship mapped. I can get records and see the relationship but I have not been able to create a record and have the foreign key persist. Currently, When a new record gets created in the parent table (FacilityGeneral) I also create a new record in the ChildTable(FacilityLocation), however, the foreign key in the child table does not get created automatically. </p>
  
  <pre><code>@Entity
  public class FacilityGeneral {
  
  @Id
  @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "facilityGenIdSeq")
  @SequenceGenerator(name = "facilityGenIdSeq", initialValue = 567, allocationSize = 1)
  @Column(updatable = false, unique = true)
  private Long generalIdPk;
  
  @NotBlank(message = "Facility Name is required")
  private String facilityName;
  
  @OneToOne(fetch = FetchType.EAGER, mappedBy = "facilityGeneral", cascade = CascadeType.PERSIST)
  @JsonIgnore
  private FacilityLocation location;
  }
  
  
  @Entity
  public class FacilityLocation {
  @Id
  @SequenceGenerator(name = "facilityLocationSeq", initialValue = 374, allocationSize = 1)
  @GeneratedValue (strategy = GenerationType.SEQUENCE, generator = "facilityLocationSeq")
  @Column(updatable= false, nullable = false, unique = true)
  private Long locationIdPk;
  
  @OneToOne (fetch = FetchType.EAGER)
  @JoinColumn (name="facilityIdFk")
  private FacilityGeneral facilityGeneral;
  </code></pre>
  
  <p>I tried to persist it programmatically by assigning the  sequence value being created as the Primary key in parent table (FacilityGeneral) to a differnt field in the Child table but was unable since the Sequence # isn't generated until the object is persisted. The actual foreign key field remained null. </p>
  
  <pre><code>public FacilityGeneral createOrUpdate(FacilityGeneral facility){
      if(facility.getGeneralIdPk() == null) {
          //create new facility
          Number nextInSeq = entityManager.createNativeQuery("SELECT FACILITY_GEN_ID_SEQ.nextval from dual").getFirstResult();
          facility.setGeneralIdPk(nextInSeq.longValue());
  
          //Create new Records for corresponding relationships
          FacilityLocation location = new FacilityLocation();
          facility.setLocation(location);
          location.setFacilityGeneral(facility);
          //had a none foreignkey field here that I tried to insert to but failed
          //location.setFacilityId(nextInSeq.LongValue());
      }
  
      return facilityGeneralRepository.save(facility);
  }
  </code></pre>
  
  <p>What am I missing in order to populate the foreign key filed (facilityIdFk) automatically with the parent table primary key?</p>