Sorry for the delay, I needed to create an SSCCE.
Before I continue: does JPA (Hibernate) allow references to non-primary key columns? Zip.country is such a case: Countries.iso_code is not null and has a unique constraint.
I reduced my original app to those four classes plus an HSQL DB test case using Hibernate 3.6. I get the following exception:
Exception in thread "main" javax.persistence.PersistenceException: [PersistenceUnit: geoareas] Unable to configure EntityManagerFactory
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:374)
at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:56)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:48)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:32)
at tld.geoareas.Main.main(Main.java:45)
Caused by: org.hibernate.MappingException: property [_tld_geoareas_bbstats_model_Zip__identifierMapper.country] not found on entity [tld.geoareas.bbstats.model.Country]
at org.hibernate.mapping.PersistentClass.getRecursiveProperty(PersistentClass.java:378)
at org.hibernate.cfg.annotations.TableBinder.bindFk(TableBinder.java:414)
at org.hibernate.cfg.ToOneFkSecondPass.doSecondPass(ToOneFkSecondPass.java:115)
at org.hibernate.cfg.Configuration.processEndOfQueue(Configuration.java:1550)
at org.hibernate.cfg.Configuration.processFkSecondPassInOrder(Configuration.java:1473)
at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1389)
at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1345)
at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1477)
at org.hibernate.ejb.EventListenerConfigurator.configure(EventListenerConfigurator.java:193)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:1096)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:278)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:362)
... 4 more
Caused by: org.hibernate.MappingException: property [_tld_geoareas_bbstats_model_Zip__identifierMapper.country] not found on entity [tld.geoareas.bbstats.model.Country]
at org.hibernate.mapping.PersistentClass.getRecursiveProperty(PersistentClass.java:424)
at org.hibernate.mapping.PersistentClass.getRecursiveProperty(PersistentClass.java:375)
... 15 more
Is this a Hibernate bug? I'm wondering about the "recursive property" here...
Karsten
PS: the answer over at SO wasn't helpful (yet).