休眠多对一外键未设置

Question

I have a fairly straightforward one-to-many relationship

[SampleAliasMask] has many [SampleAliasMaskPart]

My problem is that when I persist a new instance of SampleAliasMask with collection parts I get an constraint violation that the foreign key link from the tables of SampleAliasMaskPart to SampleAliasMask is being set to NULL.

I am mapping using hibernate annotations as such:

@Entity
@Table(name="SAMPLE_ALIAS_MASK")
public class SampleAliasMask extends ClientEntity {
    @OneToMany(mappedBy = "sampleAliasMask", fetch = FetchType.EAGER, cascade = javax.persistence.CascadeType.ALL, orphanRemoval = true)
    @Cascade(CascadeType.ALL)
    @Length(min = 1, message = "The sample alias mask must have components")
    private Set<SampleAliasMaskPart> components;

With the other half of the relationship mapped as so:

@Entity
@Table(name="SAMPLE_ALIAS_MASK_PART")
public class SampleAliasMaskPart extends ClientEntity {
    @ManyToOne(optional = false, fetch = FetchType.LAZY)
    @JoinColumn(name = "SAMPLE_ALIAS_MASK_ID", nullable = false)
    private SampleAliasMask sampleAliasMask;

The relevant part of ClientEntity is

@MappedSuperclass
public abstract class ClientEntity {
    @Id
    @Column(name="ID")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

I am creating the parts like this:

HashSet<SampleAliasMaskPart> components = new HashSet<>();
for(Map<String, Object> c : this.components) {
    SampleAliasMaskPart component = new SampleAliasMaskPart(Integer.parseInt(c.get("value").toString(), 10), c.get("name").toString());
    result.validate(component);
    components.add(component);
}
mask.setComponents(components);

The exact error I get is:

java.sql.BatchUpdateException: ORA-01400: cannot insert NULL into ("ST"."SAMPLE_ALIAS_MASK_PART"."SAMPLE_ALIAS_MASK_ID")

---

I suspect the issue has to do with the fact that I never explicitly set SampleAliasMaskPart.sampleAliasMask but why do I need to? That relationship is never exposed nor navigated. That field is only there for mapping purposes which makes me think that I'm mapping this wrong.

Answer 1

Your assumption is correct. Hibernate uses the owning side of an association to know is the association exists or not. And the owning side ai the side where there is no mappedBy attribute.

The general rule is that when you have a bidirectional association, it's your responsibility to make the object graph coherent by initializing/modifying both sides of the association. Hibernate doesn't care much about it, but if you don't initialize the owning side, it won't persist the association.

Note that you're not forced to make this association bidirectional. If you don't, then adding the part to the mask will be sufficient, because this side (which is the unique side) is the owning side.

Answer 2

JB Nizet suggested correctly. There are two ways you can solve it:

1. Removing the bi-directional relationship:Remove the annotation @ManyToOne(optional = false, fetch = FetchType.LAZY) from the simpleAliasMask in SampleAliasMaskPart

2. Add the mask to each component by doing something like component.setSimpleAliasMask(mask) . This will do the bidirectional relationship.