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https://issues.apache.org/jira/browse/OPENJPA-1253?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12756626#action_12756626
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Fay Wang commented on OPENJPA-1253:
-----------------------------------
JPA 2.0 supports non-default mapping (sec 2.9):
"In addition, this specification also requires support for the following
alternative mapping strategies: the mapping of unidirectional one-to-many
relationships by means of foreign key mappings; the mapping of unidirectional
and bidirectional one-to-one relationships, bidirectional
many-to-one/one-to-many relationships, and unidirectional many-to-one
relationships by means of join table mappings. The JoinColumn and JoinTable
annotations or corresponding XML elements must be used to specify such
non-default mappings. See sections 11.1.21 and 11.1.23."
For *toMany relation, the non-default and default mappings, according to the
spec, are:
(1) uni-/OneToMany/foreign key strategy
(2) uni-/OneToMany/join table strategy (default)
(3) bi-/OneToMany/foreign key strategy (default)
(4) bi-/OneToMany/join table strategy
(5) uni-/ManyToMany/join table strategy (default)
(6) bi-/ManyToMany/join table strategy (default)
For (1), the spec provides the following example (Sec 11.1.36):
Example 3: Unidirectional One-to-Many association using a foreign key mapping
In Customer class:
@OneToMany(orphanRemoval=true)
@JoinColumn(name="CUST_ID") // join column is in table for Order
public Set<Order> getOrders() {return orders;}
For (4), Bi-directional One-to-Many association using the join table mapping
In Customer class:
@OneToMany(mappedBy="customer")
@JoinTable(
name="Customer_Orders",
joinColumns=
@JoinColumn(name="Order_ID", referencedColumnName="ID"),
inverseJoinColumns=
@JoinColumn(name="Cust_ID", referencedColumnName="ID")
)
public Set<Order> getOrders() {return orders;}
Note that in this scenario, @JoinTable is required. Simply applying @JoinColumn
without @JoinTable will result in an exception thrown by openjpa.
Similarly for ManyToMany mapping, @JoinTable is required as shown by the
example in the spec (11.1.25). Simply applying @JoinColumn will fail with an
exception:
@ManyToMany
@JoinTable(
name="CUST_PHONE",
joinColumns=
@JoinColumn(name="CUST_ID", referencedColumnName="ID"),
inverseJoinColumns=
@JoinColumn(name="PHONE_ID", referencedColumnName="ID")
)
public Set<PhoneNumber> getPhones() { return phones; }
The failing example provided in this JIRA is not valid:
@MapKey(name = "basic")
@OneToMany(mappedBy = "oneManyOwner")
@JoinColumn(name = "asdf")
protected Map<String, AnnoTest2> inverseOwnerMapKey = new HashMap();
This is a bi-directional OneToMany assocation. If the default foreign key
strategy is intended, no JoinColumn annotation should be applied. If the
non-default join table strategy is intened, the JoinTable annotation should be
applied.
> JoinColumn annotation not allowed in conjunction with *ToMany annotation
> ------------------------------------------------------------------------
>
> Key: OPENJPA-1253
> URL: https://issues.apache.org/jira/browse/OPENJPA-1253
> Project: OpenJPA
> Issue Type: Bug
> Components: jdbc
> Affects Versions: 2.0.0-M1, 2.0.0-M2, 2.0.0-M3, 2.0.0-M4, 2.0.0
> Reporter: Rick Curtis
> Fix For: 2.0.0
>
>
> I receive the following exception if I have an Entity with a One(Many)ToMany
> relationship with another Entity.
> <openjpa-2.0.0-SNAPSHOT-r422266:805588 fatal user error>
> org.apache.openjpa.persistence.ArgumentException: You have supplied columns
> for "....Entity", but this mapping cannot have columns in this context.
> To recreate the failure, add a @JoinColumn annotation to one of the *ToMany
> relationships in org.apache.openjpa.persistence.jdbc.annotations.AnnoTest1.
> example:
> @MapKey(name = "basic")
> @OneToMany(mappedBy = "oneManyOwner")
> @JoinColumn(name = "asdf")
> protected Map<String, AnnoTest2> inverseOwnerMapKey = new HashMap();
> Then run:
> trunk\openjpa-parent\openjpa-persistence-jdbc>mvn test
> -Dtest=org.apache.openjpa.persistence.jdbc.annotations.TestOneToMany
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