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;
// ... getters and setters
}
class B {
private A a;
}
Class A's mapping specifies:
<many-to-one name="b" class="B"
insert="false" update="false"
column="id" unique="true"/>
and Class B's mapping specifies:
<one-to-one name="a" class="A" constrained="true"/>
What I would like is for b to be null when no matching row for B was found in the database. So I can do this (in class A):
if (b == null)
However, it seems that b is never null.
What can I do about this?
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
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