Persistence in JPA Cascade

Question

I’m trying to perform a cascade persistence using JPA.

I have the entity: Course and Module

• 1 Course can have several Module

  @Entity(name = "course")
  
  public class Course extends BaseEntity {
  
  private static final long serialVersionUID = 1L;
  
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column(name = "id_course")
  private Long idCourse;
  
  @SerializedName("Modules")
  @OneToMany(mappedBy = "course", cascade = CascadeType.ALL, orphanRemoval = false)
  private List<Module> modules;
  

• 1 Module can have only one Course

  @Entity(name = "module")
  public class Module extends BaseEntity {
  
  private static final long serialVersionUID = 1L;
  
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column(name = "id_module")
  private Long idModule;
  
  @OneToOne
  @JoinColumn(name = "id_course")
  private Course course;
  

I want that the moment that the Course is saved it saves all the "children - Module". As it is today, the two are persisting in the correct way. However in the table module the field id_course is turning out to be null.

Answer 1

Probably because Course is null

@OneToOne(cascade= {{CascadeType.DETACH})
@JoinColumn(name = "id_course")
private Course course;

Fill it before saving

for (Module  m : course.getModules()) {
    m.setCourse(course);
}