Hi all, I have a class Executive which inherits of the Person class. See below:

/**
*
* Mapping for Person table.
*
* @version $Id: Person.java,v 1.5 2004/03/01 22:43:18 aryjr Exp $
* @author <a href="mailto:junior@valoriza.com.br">Ary Junior</a>
*
* @hibernate.class
* table="Person"
*
*/
public class Person {
...
public void setCompany(Company company) {
this.company = company;
}
/**
*
* @hibernate.many-to-one
* column="CompanyId"
*
* @return br.com.valoriza.imf.site.persistence.Company
*/
public Company getCompany() {
return company;
}
...
}

/**
*
* Mapping for Executive table.
*
* @version $Id: Executive.java,v 1.4 2004/02/26 15:32:07 aryjr Exp $
* @author <a href="mailto:junior@valoriza.com.br">Ary Junior</a>
*
* @hibernate.joined-subclass
* table="Executive"
*
* @hibernate.joined-subclass-key
* column="PersonId"
*/
public class Executive extends Person {
...
}

I have too the Company class which have a collection of executives, see below:

public void setExecutives(Set executives) {
this.executives = executives;
}

/**
*
* @hibernate.set
* role="executives"
* table="Executive"
* order-by="Name ASC"
* cascade="all"
* readonly="true"
* inverse="true"
*
* @hibernate.collection-key
* column="CompanyId"
*
* @hibernate.collection-one-to-many
* class="br.com.valoriza.imf.site.persistence.Executive"
*
* @return java.util.Set
*/
public Set getExecutives() {
return executives;
}

Since the CompanyId column belongs to the table Person and not it Executive table, the Hibernate return the message below:

...
Caused by: java.sql.SQLException: Column not found, message from server: "Unknown column 'executives0_.CompanyId' in 'field list'"
...

Some suggestion? This is a limitation?

[]'s

Ary Junior

Show the mapping please

Ok, the Company mapping:

...
<class
name="br.com.valoriza.imf.site.persistence.Company"
table="Company"
dynamic-update="false"
dynamic-insert="false"
>

<id
name="id"
column="CompanyId"
type="int"
>
<generator class="native">
</generator>
</id>

...

<set
name="executives"
table="Executive"
lazy="false"
inverse="true"
cascade="all"
sort="unsorted"
order-by="Nome ASC"
>

<key
column="CompanyId"
/>

<one-to-many
class="br.com.valoriza.imf.site.persistence.Executive"
/>
</set>
...

</class>
...

Now the Person and Executive mapping:

<class
name="br.com.valoriza.imf.site.persistence.Person"
table="Person"
dynamic-update="false"
dynamic-insert="false"
>

<id
name="id"
column="PersonId"
type="int"
>
<generator class="native">
</generator>
</id>

<many-to-one
name="Company"
class="br.com.valoriza.imf.site.persistence.Company"
cascade="none"
outer-join="auto"
update="true"
insert="true"
column="CompanyId"
/>

...

<joined-subclass
name="br.com.valoriza.imf.site.persistence.Executive"
table="Executive"
dynamic-update="false"
dynamic-insert="false"
>
<key
column="PersonId"
/>

</joined-subclass>
...

</class>

Thanks!!!

[]'s

Ary Junior

Ah,
<key
column="CompanyId"
/>
means you must have a companyId in the Executive table

or company should be linked to Person in the one-to-many mapping

But the Company have a collection of Executives and one Responsible (another class), both inherit of Person. The Executive class and the Responsible class have different associations with the class Company however they belong to the same hierarchy. I find that my problem was to have chosen the table-per-class strategy. What you think?

Forgive me, I would have to say the table-per-concrete-class strategy.

Thanks!!!

If you've a table per concrete class hierarchy, then you should have a CompanyId column in the executive table

Why? This would not be redundant? If the Executive class inherits of the class Person, the JVM knows that it also has the method getCompany(). Then, the Hibernate would have to know that the Executive table has the CompanyId field, because it "inherits" of the table Person. Right or wrong?

Hum, you mean you have a table for Person and a table for Executive, but both are concrete classes : I've never try this case actually.

Anyway

And it knows that for sure, It asked this column:
Column not found, message from server: "Unknown column 'executives0_.CompanyId' in 'field list'"

The column must be in the Executive table.

Table-per-concrete-class strategy means no link between tables (only linked by classes), and thus redundance in DB

Hi Emmanuel, see below the relation on database:



And the association on UML:



I fear to have expressed badly when I defined adopted strategy. This is a table-per-subclass strategy, not the table-per-concrete-class strategy. I think that hibernate would have to look for the field CompanyId in the table Person and not in the Executive table. In the future this would be possible? Thanks very much for the patience.

[]s

Ary Junior

<class
name="br.com.valoriza.imf.site.persistence.Company"
table="Company"
dynamic-update="false"
dynamic-insert="false"
>

<id
name="id"
column="CompanyId"
type="int"
>
<generator class="native">
</generator>
</id>

...

<set
name="persons"
table="Person"
lazy="false"
inverse="true"
cascade="all"
sort="unsorted"
order-by="Nome ASC"
>

<key
column="CompanyId"
/>

<one-to-many
class="br.com.valoriza.imf.site.persistence.Person"
/>
</set>
...

</class>
...

Now the Person and Executive mapping:

<class
name="br.com.valoriza.imf.site.persistence.Person"
table="Person"
dynamic-update="false"
dynamic-insert="false"
>

<id
name="id"
column="PersonId"
type="int"
>
<generator class="native">
</generator>
</id>

<many-to-one
name="Company"
class="br.com.valoriza.imf.site.persistence.Company"
cascade="none"
outer-join="auto"
update="true"
insert="true"
column="CompanyId"
/>

...

<joined-subclass
name="br.com.valoriza.imf.site.persistence.Executive"
table="Executive"
dynamic-update="false"
dynamic-insert="false"
>
<key
column="PersonId"
/>

</joined-subclass>
...

</class>


When you'll do myCompany.getPersons().get(0) you'll be able to cast on Executive or Responsable depending the cases

This is not my problem. My problem is that the Hibernate does not know that the CompanyId column belongs to the Person table and not to the Executive table!!!

Have you notices the changes between your mapping and mine?

<set
name="persons"
table="Person" ---> your collection has to be mapped with person not executive
lazy="false"
inverse="true"
cascade="all"
sort="unsorted"
order-by="Nome ASC"
>

<key
column="CompanyId"
/>

<one-to-many
class="br.com.valoriza.imf.site.persistence.Person"
/>
</set>


By doing this, hibernate try to get companyId in executive Table ???

Please don't get excited....

Please forgive me for the precipitation when answering its topic. Thanks very much by the attention and patience again. But, if I get all persons of Company, I will have that to verify if each person is an executive or not with the "instanceof" operator, right? He would not be ideal if the Hibernate only returned me the executives?

what about something like HQL:
"select from Executive e where e.company.id = ?"

this try to get companyId from Persone Table or Executive Table?

I must respect the mapping file....