I am working on a legacy code base with an existing DB schema. The existing code uses SQL and PL/SQL to execute queries on the DB. We have been tasked with making a small part of the project database-engine agnostic (at first, change everything eventually). We have chosen to use Hibernate 3.3.2.GA and "*.hbm.xml" mapping files (as opposed to annotations). Unfortunately, it is not feasible to change the existing schema because we cannot regress any legacy features. The problem I am encountering is when I am trying to map a uni-directional, one-to-many relationship where the FK is also part of a composite PK. Here are the classes and mapping file... CompanyEntity.java public class CompanyEntity { private Integer id; private Set<CompanyNameEntity> names; ... } CompanyNameEntity.java public class CompanyNameEntity implements Serializable { private Integer id; private String languageId; private String name; ... } CompanyNameEntity.hbm.xml <?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.jboss.org/dtd/hibernate/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.example"> <class name="com.example.CompanyEntity" table="COMPANY"> <id name="id" column="COMPANY_ID"/> <set name="names" table="COMPANY_NAME" cascade="all-delete-orphan" fetch="join" batch-size="1" lazy="false"> <key column="COMPANY_ID"/> <one-to-many entity-name="vendorName"/> </set> </class> <class entity-name="companyName" name="com.example.CompanyNameEntity" table="COMPANY_NAME"> <composite-id> <key-property name="id" column="COMPANY_ID"/> <key-property name="languageId" column="LANGUAGE_ID"/> </composite-id> <property name="name" column="NAME" length="255"/> </class> </hibernate-mapping> This code works just fine for SELECT and INSERT of a Company with names. I encountered a problem when I tried to update and existing record. I received a BatchUpdateException and after looking through the SQL logs I saw Hibernate was trying to do something stupid... update COMPANY_NAME set COMPANY_ID=null where COMPANY_ID=? Hibernate was trying to dis-associate child records before updating them. The problem is that this field is part of the PK and not-nullable. I found the quick solution to make Hibernate not do this is to add "not-null='true'" to the "key" element in the parent mapping. SO now may mapping looks like this... CompanyNameEntity.hbm.xml <?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.jboss.org/dtd/hibernate/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.example"> <class name="com.example.CompanyEntity" table="COMPANY"> <id name="id" column="COMPANY_ID"/> <set name="names" table="COMPANY_NAME" cascade="all-delete-orphan" fetch="join" batch-size="1" lazy="false"> <key column="COMPANY_ID" not-null="true"/> <one-to-many entity-name="vendorName"/> </set> </class> <class entity-name="companyName" name="com.example.CompanyNameEntity" table="COMPANY_NAME"> <composite-id> <key-property name="id" column="COMPANY_ID"/> <key-property name="languageId" column="LANGUAGE_ID"/> </composite-id> <property name="name" column="NAME" length="255"/> </class> </hibernate-mapping> This mapping gives the exception... org.hibernate.MappingException: Repeated column in mapping for entity: companyName column: COMPANY_ID (should be mapped with insert="false" update="false") My problem now is that I have tryed to add these attributes to the key-property element but that is not supported by the DTD. I have also tryed changing it to a key-many-to-one element but that didn't work either. So... How can I map "insert='false' update='false'" on a composite-id key-property which is also used in a one-to-many FK?