I googled all day and I cant find one good example how to map this kind of objects:
class Parent{
private Integer parentId;
private String parentName;
private List<Child> childs;
// ....... getters and setters ............
}
class Child{
private Integer childId;
private String childName;
private Parent parent;
// ....... getters and setters ...........
}
I have no idea how to make map for this kind of List.
Hibernate documentation has plenty of examples, including this one which is basically what you're looking for. XML mapping would for your case would look like:
<class name="Parent" table="Parent">
<id name="parentId" column="id" type="integer" /> <!-- TODO: specify generator -->
<property name="parentName" type="string" column="name" />
<bag name="childs" table="Children" inverse="true">
<key column="parent_id" />
<one-to-many class="Child" />
</bag>
</class>
<class name="Child" table="Children">
<id name="childId" column="id" type="integer" /> <!-- TODO: specify generator -->
<property name="childName" type="string" column="name" />
<many-to-one name="parent" column="parent_id" not-null="true"/>
</class>
For examples of annotation-based mapping take a look here
<bag> can be replaced with <list> but you'll need another column in the Children table to maintain element indexes.First of all, you should declare your List<Child> as IList<Child>, because NHibernate needs to be able to use its own collection-type that implements IList.
In your mapping, you should use the 'bag' element to map your List. (Are you sure you want to use a List and not a Set ? Since a List allows that one single entity occurs more then once in the list, whereas a Set does not allow that).
This is how I should do it:
public class Parent
{
private IList<Child> _children = new List<Child>();
public ReadOnlyCollection<Child> Children
{
get {return _children.AsReadOnly();}
}
}
And the mapping:
<class name="Parent" table="Parent">
<list name="Children" table="..." access="field.camelcase-underscore" inverse="true">
<key column="..." />
<one-to-many class="Child" />
</list>
</class>
(Ommitted al the other properties for brevity)
(Ow, now that I see it, you're using Hibernate ? My code example is in C#, so I do not know whether you have the notion of ReadOnlyCollection etc...)
