Hello Jeff,
OpenJPA supports the cited example where Page using a composite ID which
in turn refers to Book's composite ID.
Book/Page/Library classes work with
a) openjpa-0.9.7 (do not know whether observed errors are due to usage
of earlier 0.9.6 version)
b) following modifications in Page.book field (with a + sign)
@Id
@Column(nullable = false)
@ManyToOne (cascade = CascadeType.ALL)
+ @JoinColumns({
+ @JoinColumn(name="book_library_LIBRARY_NAME",
referencedColumnName="library_LIBRARY_NAME"),
+ @JoinColumn(name="book_BOOK_NAME",
referencedColumnName="BOOK_NAME")
})
private Book book;
where the JoinColumns specification refers to following schema (as per
your Page/Book/Library class annotations):
mysql> desc book;
+----------------------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------------------+--------------+------+-----+---------+-------+
| library_LIBRARY_NAME | varchar(255) | NO | PRI | NULL | |
| BOOK_NAME | varchar(255) | NO | PRI | NULL | |
+----------------------+--------------+------+-----+---------+-------+
mysql> desc page;
+---------------------------+--------------+------+-----+---------+-----
--+
| Field | Type | Null | Key | Default |
Extra |
+---------------------------+--------------+------+-----+---------+-----
--+
| book_library_LIBRARY_NAME | varchar(255) | NO | PRI | NULL |
|
| book_BOOK_NAME | varchar(255) | NO | PRI | NULL |
|
| PAGE_NUMBER | int(11) | NO | PRI | NULL |
|
+---------------------------+--------------+------+-----+---------+-----
--+
Without explicitly naming the join columns, following error is
generated:
Caused by: <4|true|0.9.7-incubating-SNAPSHOT>
org.apache.openjpa.persistence.ArgumentException: "crxxx.Page.book" does
not supply a name for at least one declared column. Since this mapping
can involve multiple columns or uses constant joins, each column must
give either its name or a non-constant target.
at
org.apache.openjpa.jdbc.meta.MappingInfo.mergeJoinColumn(MappingInfo.jav
a:1372)
at
org.apache.openjpa.jdbc.meta.MappingInfo.createJoins(MappingInfo.java:11
86)
at
org.apache.openjpa.jdbc.meta.MappingInfo.createForeignKey(MappingInfo.ja
va:948)
at
org.apache.openjpa.jdbc.meta.ValueMappingInfo.getTypeJoin(ValueMappingIn
fo.java:101)
at
org.apache.openjpa.jdbc.meta.strats.RelationFieldStrategy.map(RelationFi
eldStrategy.java:144)
at
org.apache.openjpa.jdbc.meta.FieldMapping.setStrategy(FieldMapping.java:
117)
at
org.apache.openjpa.jdbc.meta.RuntimeStrategyInstaller.installStrategy(Ru
ntimeStrategyInstaller.java:77)
at
org.apache.openjpa.jdbc.meta.FieldMapping.resolveMapping(FieldMapping.ja
va:435)
at
org.apache.openjpa.jdbc.meta.FieldMapping.resolve(FieldMapping.java:400)
at
org.apache.openjpa.jdbc.meta.ClassMapping.resolveNonRelationMappings(Cla
ssMapping.java:810)
at
org.apache.openjpa.jdbc.meta.MappingRepository.prepareMapping(MappingRep
ository.java:316)
at
org.apache.openjpa.meta.MetaDataRepository.preMapping(MetaDataRepository
.java:602)
at
org.apache.openjpa.meta.MetaDataRepository.resolve(MetaDataRepository.ja
va:489)
... 24 more
NestedThrowables:
<4|true|0.9.7-incubating-SNAPSHOT>
org.apache.openjpa.persistence.ArgumentException: Field
"crxxx.Book.pages" declares "crxxx.Page.book" as its mapped-by field,
but this field is not a direct relation.
at
org.apache.openjpa.jdbc.meta.strats.RelationToManyInverseKeyFieldStrateg
y.map(RelationToManyInverseKeyFieldStrategy.java:123)
at
org.apache.openjpa.jdbc.meta.strats.RelationCollectionInverseKeyFieldStr
ategy.map(RelationCollectionInverseKeyFieldStrategy.java:92)
at
org.apache.openjpa.jdbc.meta.FieldMapping.setStrategy(FieldMapping.java:
117)
at
org.apache.openjpa.jdbc.meta.RuntimeStrategyInstaller.installStrategy(Ru
ntimeStrategyInstaller.java:77)
at
org.apache.openjpa.jdbc.meta.FieldMapping.resolveMapping(FieldMapping.ja
va:435)
at
org.apache.openjpa.jdbc.meta.FieldMapping.resolve(FieldMapping.java:400)
at
org.apache.openjpa.jdbc.meta.ClassMapping.resolveMapping(ClassMapping.ja
va:781)
at
org.apache.openjpa.meta.ClassMetaData.resolve(ClassMetaData.java:1570)
...
Pinaki Poddar
BEA Systems
415.402.7317
-----Original Message-----
From: jeff [mailto:[EMAIL PROTECTED]
Sent: Monday, April 02, 2007 12:42 PM
To: open-jpa-dev@incubator.apache.org
Subject: composite ID w/ another composite ID as a field
say i have Library, Book, and Page classes. a Library has many Books,
and a Book has many Pages. A Library's ID is it's name (simple). A
Book's ID is a composite of it's name and it's owning Library's name
(bidirectional relationship). A Page's ID is a composite of it's number
and it's owning Book's ID, a BookID.
so, the PageId class starts like:
public class PageId implements Serializable {
private int number;
private BookId book;
the error i'm getting is at runtime ...
<4|true|0.9.6-incubating>
org.apache.openjpa.persistence.ArgumentException: Field
"com.mycompany.book.Book.pages" declares "com.mycompany.book.Page.book"
as its mapped-by field, but this field is not a direct relation.
first, is what i'm trying to do even valid? i suspect it is not, and the
problem is that the fields of the ID class must be "simple" types (i
believe the spec demands that). although, the error message is a little
confusing so i am not sure.
it occurs to me that another way to achieve this would be to add
bookName and libraryName fields to the Page class, and add a @PrePersist
method that populates them by calling book.getName() and
book.getLibrary().getName(). but again this is messy because that data
is already in the table because of the bidirectional relationship
between the objects.
as always, i'm open to "what are you an idiot?" responses if i am just
going about trying to define the Library, Book, Page relationship in an
obtuse manner.
classes attached.
________________________________
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