Newbie Question one-to-many

painlessprod · **Posted:** Thu Dec 07, 2006 5:19 pm

I have something simple:

Code:

public class Person 
{ 
private int m_PersonID 
List<Address> m_Addresses; 
 
public Person() 
{  
} 
public int PersonID{get{return m_PersonID;}set{m_personID=value;}} 
public List<Address> Addresses{get{return m_Addresses;}set{m_Addresses=value;}} 
} 
 
public class Address 
{ 
private int m_AddressID 
public Address() 
{ 
} 
public int AddressID{get{return m_AddressID;}set{m_AddressID=value;}} 
} 

I have 3 tables that create this mapping, since i want to support addresses belonging to things other than Person
TABLES: Person, Address, PersonAddress
I have Keys inside the tables that link the 2 classes together via PersonAddress, PersonAddress table contains PersonAddressID, PersonID, and AddressID.
Simple RDBMS
I have seen many examples on the help notes about linking direct ie Person directly Many to One on address, but since address is a property of Person and could also be a property of other classes such as Corporation(), i dont want to tie the classes together directly.
How do I represent this in hbm.xml

Thanks in advance and excuse my ignorance.

onevextchuck · **Posted:** Fri Dec 08, 2006 5:57 pm

Hello

Creating relationships between two objects in NHibernate does not mean that those objects can not be related to other objects. Your decision on whether to use a many-to-many or a many-to-one should be solely based on whether or not a person can have more than one address.

For instance if companies and people only had one address, you could have three tables and classes: Company, Person and Address. All three have primary keys. Both the Person table and Company table contain a column addressId that has a foreign key defined where the primary key is the Address table primary key column.

Code:

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.0" namespace="Savo.SAM.Business" assembly="Savo.SAM.Business">
   <class name="Address" table="`Address`">
      <id name="Id">
         <column name="id" not-null="true" />
         <generator class="identity"/>
      </id>
   </class>
   <class name="Person" table="`Person`">
      <id name="Id">
         <column name="id" not-null="true" />
         <generator class="identity"/>
      </id>
      <many-to-one name="Address" column="addressId" class="Address"/>
   </class>
   <class name="Company" table="`Company`">
      <id name="Id">
         <column name="id" not-null="true" />
         <generator class="identity"/>
      </id>
      <many-to-one name="Address" column="addressId" class="Address"/>
   </class>

You could also throw in a couple of one-to-many inverse relationships on the Address class mapping to see which people and companies use that address. If you wanted both to be many to many relationships, you would need five tables, but it would work just fine. There are also other more complex solutions involving inheritance, but those approaches are usually overkill and only serve to confuse unless absolutely necessary.

painlessprod · **Posted:** Mon Dec 11, 2006 9:15 am

thnks for your post, but the problem is the fact that there is a one-to-many relationship, a person can have multiple addresses, nor do i want to hardcode the relationship between address and person without a join table because of my aforementioned problem, that an address can be owned by other entitys than Person()