Embeded Id Field Generated as BLOB instead of Long

Question

Using the shema generator of hibernate 3.6

org.hibernate.cfg.Configuration.generateSchemaCreationScript

And with thoses models definition :

 @Entity
 @Table(name="ERP_Period")
 @PrimaryKeyJoinColumn(name = "id")
 public class ErpPeriod extends Record{
    @EmbeddedId
    private PeriodId codeId;
    @Override
    public PeriodId getCodeId() {   
        return codeId;
    }
    public void setCodeId(PeriodId codeId) {
        this.codeId = codeId;
    }                       
 }
    @Embeddable
    public class PeriodId {
        private ErpFolder folder;
        private int exercice;
        private int period;     
        public ErpFolder getFolder() {
        return folder;
        }
        public void setFolder(ErpFolder folder) {
        this.folder = folder;
        }
    }
    @Entity
    @Table(name="ERP_Folder")
    @PrimaryKeyJoinColumn(name = "id")
    public class ErpFolder extends AbsErpFolder{    
        @Id
        @GeneratedValue(strategy=GenerationType.AUTO)
        private Long codeId;
        @Override
        public Long getCodeId() {
        return codeId;
        };
        public void setCodeId(Long codeId) {
        this.codeId = codeId;
        }
    }

The generator genrates the ErpFolder field as BLOB instead of Long id of the ErpFolder :

create table ERP_Period (exercice integer not null, folder blob not null, period integer not null, label varchar(255), primary key (exercice, folder, period))

With the result of the Database exception ( which is normal ):

org.firebirdsql.jdbc.FBSQLException: GDS Exception. 335544351. unsuccessful metadata update
 attempt to index BLOB column in INDEX RDB$PRIMARY13
null