How do I map a one-to-one value type association in an joined-subclass?
- by David Rubin
I've got a class hierarchy mapped using table-per-subclass, and it's been working out great:
class BasicReport
{
...
}
class SpecificReport : BasicReport
{
...
}
With mappings:
<class name="BasicReport" table="reports">
<id name="Id" column="id">...</id>
<!-- some common properties -->
</class>
<joined-subclass name="SpecificReport" table="specificReports" extends="BasicReport">
<key column="id"/>
<!-- some special properties -->
</joined-subclass>
So far, so good. The problem I'm struggling with is how to add a property to one of my subclasses that's both a value type for which I have an IUserType implemented and also mapped via an association:
class OtherReport : BasicReport
{
public SpecialValue V { get; set; }
}
class SpecialValueUserType : IUserType
{
...
}
What I'd like to do is:
<joined-subclass name="OtherReport" table="otherReports" extends="BasicReport">
<key column="id"/>
<join table="rptValues" fetch="join">
<key column="rptId"/>
<property name="V" column="value" type="SpecialValueUserType"/>
</join>
</joined-subclass>
This accurately reflects the intent, and the pre-existing database schema I'm tied to: the SpecialValue instance is a property of the OtherReport, but is stored in a separate table ("rptValues").
Unfortunately, it seems as though I can't do this, because <join> elements can't be used in <joined-subclass> mappings. <one-to-one> would require creating a class mapping for SpecialValue, which doesn't make any sense given that SpecialValue is just a meaningful scalar.
So what can I do? Do I have any options? Right now I'm playing a game with sets:
class OtherReport : BasicReport
{
public SpecialValue V
{
get { return _values.Count() > 0 ? _values.First() : null; }
set { _values.Clear(); _values.Add(value); }
}
private ICollection<SpecialValue> _values;
}
With mapping:
<joined-subclass name="OtherReport" table="otherReports" extends="BasicReport">
<key column="id"/>
<set name="_values" access="field" table="rptValues" cascade="all-delete-orphan">
<key column="rptId" />
<element column="value" type="SpecialValueUserType"/>
</set>
</joined-subclass>
Thanks in advance for the help! I've been banging my head into my desk for several days now.
