[Hibernate-issues] [Hibernate-JIRA] Created: (HHH-1926) Mapping a many-to-many to part of the target's composite PK doesn't work

[Daniel H. (JIRA) <no...@at...>]

Mapping a many-to-many to part of the target's composite PK doesn't work 
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         Key: HHH-1926
         URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1926
     Project: Hibernate3
        Type: Bug

  Components: core  
    Versions: 3.1.3    
 Environment: Tested on 3.1.3 and 3.2.0.cr2
    Reporter: Daniel Hannum
 Attachments: hibernateTest.zip

Hi, I brought this up on the forums:

http://forum.hibernate.org/viewtopic.php?p=2315103#2315103

And although I received some guidance, it still doesn't work. Perhaps it's a bug, perhaps it's impossible, perhaps a wider audience can help... here goes.

Consider 

class A with a 3-way PK: C1, C2, C3
class B with a 4-way PK: C2, C3, C4, C5

As you can see A and B share two columns. This is a many-to-many relation with no join table, and yes I know it's poor database design. It's legacy, can't change it, etc.

All I want is for Hibernate, when creating a persistent A, to efficiently retrieve a bag of all B's that share the two shared columns. The reverse mapping is optional. I don't need to be able to update this collection, just read the B's without having to issue separate DB hits.

Unfortunately, Hibernate is still unhappy with my mappings (below)

org.hibernate.MappingException: collection element mapping has wrong number of columns: hibernatetest.B.relatedAs type: hibernatetest.A

A.hbm.xml is

<composite-id name="compId" class="hibernatetest.APK">
	<key-property name="column1" column="C1" />
	<key-property name="column2" column="C2" />
	<key-property name="column3" column="C3" />
</composite-id>

<property name="otherColumnA" column="OTHER_COLUMN_A" />

<properties name="keysSharedA">
	<property name="column2" column="C2" insert="false" update="false"/>
	<property name="column3" column="C3" insert="false" update="false"/>
</properties>
		
<bag name="relatedBs">
	<key property-ref="keysSharedA">
		<column name="C2"/>
		<column name="C3"/>
	</key>
	<many-to-many class="hibernatetest.B"/>
</bag>

B.hbm.xml is very similar

<composite-id name="compId" class="hibernatetest.BPK">
	<key-property name="column2" column="C2" />
	<key-property name="column3" column="C3" />
	<key-property name="column4" column="C4" />
	<key-property name="column5" column="C5" />
</composite-id>

<property name="otherColumnB" column="OTHER_COLUMN_B" />
		
<properties name="keysSharedB">
	<property name="column2" column="C2" insert="false" update="false"/>
	<property name="column3" column="C3" insert="false" update="false"/>
</properties>
	
<bag name="relatedAs" inverse="true">
	<key property-ref="keysSharedB">
		<column name="C2"/>
		<column name="C3"/>
	</key>
	<many-to-many class="hibernatetest.A"/>
</bag>

I have attached a zip containing the code and mapping files, as well as a unit test that displays the problem.

Thanks for any help you can provide.

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