@Entity
public class Item implements Serializable {
   
   private static final long serialVersionUID = 8635086262992868784L;

   @EmbeddedId
   public ItemPK itemPK;
      
   @Column(name = "ITM_ITEM_NAME")
   private String itemName;
}

@Embeddable
public class ItemPK implements Serializable {
   
   private static final long serialVersionUID = -5177491823551943094L;
      
   @OneToMany(mappedBy="itemPK")
   private Set<ItemCrossReference> itemCrossReferences;
   
       @Column(name="ITM_COMP_ID", nullable=false)
   private String companyId;   
   
       @Column(name="ITM_ITEM_CODE", nullable=false)
   private String itemCode;
   
   // setter/ getter ...
   
   public void setItemCrossReferences(Set<ItemCrossReference> itemCrossReferences) {
      this.itemCrossReferences = itemCrossReferences;
   }

   public Set<ItemCrossReference> getItemCrossReferences() {
      return itemCrossReferences;
   }
   
   public boolean equals(Object other) {
      if (other instanceof ItemPK) {
         final ItemPK otherItemPK = (ItemPK) other;
         return (otherItemPK.companyId.equals(companyId) && otherItemPK.itemCode.equals(itemCode));
      }
      return false;
   }

   public int hashCode() {
      return super.hashCode();
   }
}

@Entity
public class ItemCrossReference {

   @EmbeddedId
   public ItemCrossReferencePK itemCrossReferencePK;
   
   @ManyToOne
   @JoinColumns( {
         @JoinColumn(name = "REF_MANUF_CMP_CODE", referencedColumnName = "ITM_COMP_ID"),
         @JoinColumn(name = "REF_MANUF_REF_CODE", referencedColumnName = "ITM_ITEM_CODE") })
   protected Item manufItem;
   
   @Embedded
   protected CreationDetails creationDetails;

}

Caused by: org.hibernate.AnnotationException: mappedBy reference an unknown target entity property: model.ItemCrossReference.itemPK in model.Item.itemCrossReferences
   at org.hibernate.cfg.annotations.CollectionBinder.bindStarToManySecondPass(CollectionBinder.java:578)
   at org.hibernate.cfg.annotations.CollectionBinder$1.secondPass(CollectionBinder.java:543)
   at org.hibernate.cfg.CollectionSecondPass.doSecondPass(CollectionSecondPass.java:43)
   at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1130)
   at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:329)
   at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1115)
   at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1226)
   at org.hibernate.ejb.EventListenerConfigurator.configure(EventListenerConfigurator.java:173)
   at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:854)
   at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:425)
   at org.hibernate.ejb.HibernatePersistence.createContainerEntityManagerFactory(HibernatePersistence.java:131)
   at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:224)
   at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:291)
   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1369)
   at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1335)