I found a lot of exemple on how to handle the many-to-one, many-to-many association but not the many-to-zero association. The problem is when there is no association data that cause a null error. How should I map my association to avoid the null problem?

This is the mapping section code that causing me the null problem:

<many-to-one name="followup"
class="SAP.BusinessObjects.Followup"
cascade="all"
not-null="true"
column= "TEXT_ID"
insert = "false"
update = "false"/>

What should I write instead???

Please could you help.

Hibernate version:
2.1.6
Mapping documents:
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping >

<class name="SAP.BusinessObjects.Request"
table="SAMPLES">

<id name="id" type="java.lang.Integer" column="SAMPLE_NUMBER" unsaved-value="0">
<generator class="sequence">
<param name="sequence">SAMPLE_SEQ</param>
</generator>
</id>

<property name="textid"
type="java.lang.String"
length="30"
column="TEXT_ID"/>

<many-to-one name="practitioner"
class="SAP.BusinessObjects.User"
column= "X_REQ_ID" />

<component name="site" class="SAP.BusinessObjects.Site">
<property name="sitename"
type="java.lang.String"
length="20"
not-null="false"
column="X_REQ_COMPANY"/>
<property name="contactname"
type="java.lang.String"
length="50"
column="X_REQ_CONTACT"/>

</component>


<component name="apatient" class="SAP.BusinessObjects.Patient">
<property name="initials"
type="java.lang.String"
length="50"
column ="X_PAT_ID"/>

<property name="gender"
type="java.lang.String"
length="1"
column ="X_PAT_GENDER"/>

</component>

<many-to-one name="followup"
class="SAP.BusinessObjects.Followup"
cascade="all"
not-null="true"
column= "TEXT_ID"
insert = "false"
update = "false"/>

</class>
<query name = "SAP.BusinessObjects.Request.SarInfo">
<![CDATA[from Request request
where request.textid like :textid

]]>
</query>


</hibernate-mapping>


Code between sessionFactory.openSession() and session.close():
Session session=HibernateUtil.getSession();
followupid= followupid + "%";

try{
HibernateUtil.beginTransaction();
Query query = session.getNamedQuery("SAP.BusinessObjects.Request.FollowupInfo");
query.setString("followupid", followupid);

return query.list();

}catch (HibernateException ex){
session.close();
throw new HibernateException (ex);
}
Full stack trace of any exception that occurs:
testAddRequestToWrapper: SAP.Utility.InfrastructureException: net.sf.hibernate.HibernateException: Session is closed

Name and version of the database you are using:
Oracle 9

The generated SQL (show_sql=true):

Hibernate: select request0_.SAMPLE_NUMBER as SAMPLE_N4_, request0_.TEXT_ID as TEXT_ID, request0_.PRIORITY as PRIORITY, request0_.X_MFG_PO as X_MFG_PO, request0_.X_REQ_ID as X_REQ_ID, request0_.X_REQ_COMPANY as X_REQ_CO8_, request0_.X_REQ_CONTACT as X_REQ_CO9_, request0_.X_REQ_ADDRESS1 as X_REQ_A10_, request0_.X_REQ_ADDRESS2 as X_REQ_A11_, request0_.X_REQ_CITY as X_REQ_CITY, request0_.X_REQ_PROVINCE as X_REQ_P13_, request0_.X_REQ_POSTCODE as X_REQ_P14_, request0_.X_REQ_PHONE as X_REQ_P15_, request0_.X_REQ_FAX as X_REQ_FAX, request0_.X_DRUG_BRAND_NAME as X_DRUG_17_, request0_.X_MFG_NAME as X_MFG_NAME, request0_.X_DRUG_ROUTE as X_DRUG_19_, request0_.X_DRUG_FORM as X_DRUG_20_, request0_.X_PAT_ID as X_PAT_ID, request0_.X_PAT_GENDER as X_PAT_GE3_ from SAMPLES request0_ where (request0_.TEXT_ID like ? )
Hibernate: select user0_.REQ_ID as REQ_ID1_, user0_.LAST_NAME as LAST_NAME1_, user0_.DESCRIPTION as DESCRIPT3_1_, user0_.FIRST_NAME as FIRST_NAME1_, user0_.MIDDLE_NAME as MIDDLE_N5_1_, user0_.TITLE as TITLE1_, user0_.CHANGED_ON as CHANGED_ON1_, user0_.ACTIVE as ACTIVE1_, user0_.PSWD as PSWD1_, user0_.SALT as SALT1_, user0_.USERNAME as USERNAME1_, user0_.EXPIRED as EXPIRED1_, user0_.PHONE as PHONE1_, user0_.FAX as FAX1_, user0_.EMAIL as EMAIL1_, user0_.PRIM_LOC as PRIM_LOC1_, site1_.SITE_ID as SITE_ID0_, site1_.CONTACT_NAME as CONTACT_2_0_, site1_.SITE_NAME as SITE_NAME0_, site1_.ADDRESS1 as ADDRESS10_, site1_.ADDRESS2 as ADDRESS20_, site1_.CITY as CITY0_, site1_.PROVINCE as PROVINCE0_, site1_.POSTCODE as POSTCODE0_, site1_.PHONE as PHONE0_, site1_.FAX as FAX0_, site1_.EMAIL as EMAIL0_ from X_REQUESTORS user0_ left outer join X_SITES site1_ on user0_.PRIM_LOC=site1_.SITE_ID where user0_.REQ_ID=?
Hibernate: select followup0_.FOLLOWUP_ID as FOLLOWUP1_0_, followup0_.FOLLOWUP_STATUS as FOLLOWUP2_0_, followup0_.FOLLOWUP_OBSERVATIONS as FOLLOWUP3_0_ from X_FOLLOWUPS followup0_ where followup0_.FOLLOWUP_ID=?

Debug level Hibernate log excerpt:

I don't know if that may help. I just find out that if I write my HQL in my xml file the way show below, it work


<query name = "SAP.BusinessObjects.Request.SarInfo">
<![CDATA[select request.textid
from Request request
left join request.followup up
where request.textid like :textid
and up.status is null

]]>
</query>

But I need to display all fields that normally the SQL will begin like this:

Select *
from......

So is there a way to fix the problem???? since that way I control the null problem?

Thanks

Fixed the problem.

If I'm right a set, list, bag or other are used for association one-to-many, many-to-many so do the same for a many-to-zero association and it's worked as it should be. The null problem can be controlled through a query.

If I'm wrong your output is welcome.