I\'m trying to map a one to \"zero or one\" relationship in Hibernate. I think I may have found a way using a many-to-one.
class A {
private B b;
// .
Like Boden said, the answer is to add not-found="ignore"
to the many-to-one statement in A. Doing this with annotation:
In Class A:
@ManyToOne
@Cascade({ CascadeType.ALL })
@JoinColumn(name = "Id")
@NotFound(action=NotFoundAction.IGNORE)
private B b
in Class B:
@Id
@GeneratedValue(generator = "myForeignGenerator")
@org.hibernate.annotations.GenericGenerator(
name = "myForeignGenerator",
strategy = "foreign",
parameters = @Parameter(name = "property", value = "a")
)
private Long subscriberId;
@OneToOne(mappedBy="b")
@PrimaryKeyJoinColumn
@NotFound(action=NotFoundAction.IGNORE)
private A a;
The answer was to add not-found="ignore" to the many-to-one statement in A:
<many-to-one name="b" class="B" not-found="ignore" insert="false" update="false" column="id" unique="true"/>
I tried simply adding lazy="false" to B as Rob H recommended, but that resulted in a HibernateObjectRetrievalFailureException everytime I loaded an A that had no B.
See this thread for more information:
https://forum.hibernate.org/viewtopic.php?p=2269784&sid=5e1cba6e2698ba4a548288bd2fd3ca4e
Try setting lazy="false" on the many-to-one element. That should force Hibernate to try to fetch the association ("B") when the first object ("A") is loaded. The property in "A" will either be initialized with a real instance of "B" or null.