Parent Id null in @OneToMany mapping JPA

Question

I am using javax.persistence.OneToMany relationship in a Parent Child relationship. The parent Id is coming as null, I have read through all the related post in Stackoverflo

Answer 1

I know it's too late but you can also do...

Parent Class:

@Entity
@Table(name = "DIVERSITY_TEMPLATE")
public class DiversityTemplate implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name = "DIVERSITY_TEMPLATE_ID", sequenceName = "DIVERSITY_TEMPLATE_ID", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "DIVERSITY_TEMPLATE_ID")
    @Column(name = "DIVERSITY_TEMPLATE_ID")
    private Integer diversityTemplateId;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name = "DIVERSITY_TEMPLATE_ID")
    private List attributes = new ArrayList<>();

Child Class:

@Entity
@Table(name = "DIVERSITY_TEMPLATE_ATTRIBUTE")
@TypeName("DiversityTemplateAttribute")
public class DiversityTemplateAttribute implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name = "DIVERSITY_TEMPLATE_ATTR_ID", sequenceName = "DIVERSITY_TEMPLATE_ATTR_ID", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "DIVERSITY_TEMPLATE_ATTR_ID")
    @Column(name = "DIVERSITY_TEMPLATE_ATTR_ID")
    private Integer diversityTemplateAttributeId;

    @ManyToOne(fetch = FetchType.LAZY)
    private DiversityTemplate diversityTemplate;

Service Class:

diversityTemplateRepository.save(diversityTemplate);

This way you DON'T NEED TO DO PARENT ENTRY IN EACH CHILD. it will do by itself. you just need to save parent that's it.

Quick steps what I did.

1. Removed mappedBy from Parent.
2. Added @JoinCollumn foreign key in Parent
3. Removed @JoinCollumn from Child.

Hope it helps.