Entity Relationships

@OneToMany

In regards to one-to-many unidirectional, the relationships aren't inserted at the same time so your foreign key must not be "NOT NULL" in order for the following to work (at least on Oracle):

   SQL 
   ===================================
   create table PORTAL (
         id not null primary key,
         name varchar2(50)
   );
   create table PORTAL_AREA (
        id not null primary key,
        portal_id number -- should not be 'non null'
   );
   JAVA
   ============================
   @Entity
   public class Portal {
        ...
       @OneToMany
       @JoinColumn( name = "PORTAL_ID" )
       public Collection getPortalAreas() {
         ...
       }
   }
   @Entity
   public class PortalArea (
       // no ref to portal here
   )