Composite key's problem : Foreign key must have same number of columns as referenced primary key

In this scenario :

ClassA has two composite keys : key1 and key2
ClassA's instance may have zero or more ClassB.
ClassB has three composite keys : key1 , key2 and key3
ClassA has a method getClassBSet() to get the containing ClassB.


In the mapping :




But when Hibernate is mapping collection , some error occurs :

Error while initialize foo HibernateSession's sessionFactory
net.sf.hibernate.MappingException: Foreign key must have same number of columns as referenced primary key
at net.sf.hibernate.mapping.ForeignKey.setReferencedTable(ForeignKey.java:33)
at net.sf.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:514)
at net.sf.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:614)


It seems that Hibernate requires that ClassB must have identical foreign keys to ClassA's primary key , isn't it ?
But in this scenario , it seems inevitalbe....
Can somebody solve this problem ?

I am using Hibernate 2.0.2


I know Hibernate discourages us to use composite keys ,
it encourage us to 'combine' composite keys to one independent class.
But for some historical reason , I have to design this way.

Your mapping looks perfect to me. I don't think the bit you just showed is what is causing the exception. I bet you have other stuff you are hiding from me :)

Hi , I cannot find what information I hide ....
But ... after I migrate to Hibernate 2.1 beta 2 ,
the error messages are different :

First , it says that the second key int the Set is not allowed :



Error parsing XML: XML InputStream(22)
org.xml.sax.SAXParseException: 元件 "set" 在此不允許 "key"。 (it is big5 output message , means 'key' is not allowed in the element 'set')
at org.apache.crimson.parser.Parser2.error(Parser2.java:3160)
at org.apache.crimson.parser.ValidatingParser$ChildrenValidator.consume(ValidatingParser.java:349)
at org.apache.crimson.parser.Parser2.maybeElement(Parser2.java:1317)
at org.apache.crimson.parser.Parser2.content(Parser2.java:1779)


INFO: processing one-to-many association mappings
2003/9/1 05:03:48 net.sf.hibernate.cfg.Binder bindCollectionSecondPass
INFO: Mapping collection: foo.ClassA.ClassBSet -> ClassB
2003/9/1 05:03:48 net.sf.hibernate.cfg.Configuration secondPassCompile
INFO: processing one-to-one association property references
2003/9/1 05:03:48 net.sf.hibernate.cfg.Configuration secondPassCompile
INFO: processing foreign key constraints
Error while initialize foo HibernateSession's sessionFactory

net.sf.hibernate.MappingException: Foreign key (ClassB [key2])) must have same number of columns as the reference primary key (ClassA [key1,key2])

at net.sf.hibernate.mapping.ForeignKey.setReferencedTable(ForeignKey.java:56)
at net.sf.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:557)
at net.sf.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:651)

Oh woops!


I didn't notice that the XML was invalid!

Should be:





Always check the Hibernate log for validatin errors!

Thank you , it solved !!!