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Home » Eclipse Projects » EclipseLink » @ManyToOne relation problem
@ManyToOne relation problem [message #387082] Fri, 10 April 2009 14:30 Go to next message
Somebody Somebody is currently offline Somebody SomebodyFriend
Messages: 2
Registered: July 2009
Junior Member
Hi,

I have a dilemma:

+ I have 2 entities with a ManyToOne relationship and no unique ids
(Embedded ids):

Entity A (date, field1, field2)
Entity B (field1, field2, startDate, endDate)

+ Primary key of Entity B is an embedded id composed by field1, field2,
and startDate.

+ Relationship between EntityA and EntityB

SELECT EntityB.*
FROM EntityA, EntityB
WHERE EntityB.field1 = EntityA.field1
AND EntityB.field2 = EntityA.field2
AND EntityB.startDate <= EntityA.date
AND EntityB.endDate > EntityA.date

It always return an unique row.

=> Is it possible to establish the relationship between EntityA and Entity B
with JPA annotations to fetch EntityA rows or I need to use a JPQL query to
make the join ?

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Re: @ManyToOne relation problem [message #387088 is a reply to message #387082] Tue, 14 April 2009 08:15 Go to previous messageGo to next message
Somebody Somebody is currently offline Somebody SomebodyFriend
Messages: 2
Registered: July 2009
Junior Member
Any idea ?

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Re: @ManyToOne relation problem [message #387094 is a reply to message #387082] Wed, 15 April 2009 13:32 Go to previous message
James Sutherland is currently offline James SutherlandFriend
Messages: 1939
Registered: July 2009
Location: Ottawa, Canada
Senior Member
JPA only allows relationships to be define using foreign keys
(JoinColumn). However in EclipseLink you can define complex relationships
such as this using the Expression criteria API and a DescriptorCustomizer.

See,
http://wiki.eclipse.org/EclipseLink/Examples/JPA/MappingSele ctionCriteria

---
James
http://www.nabble.com/EclipseLink---Users-f26658.html

James : Wiki : Book : Blog : Twitter

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