Many-to-one relation with default item

v.abramchuk · **Joined:** Fri Jun 20, 2008 8:24 am **Posts:** 7

Hello
My question is about many-to-one or one-to-one mapping.
I have a Profile and BillingInfo classes.

Code:

  <class name="Profile" table="Profile">       
      <id name="Id">
         <column name="Id" not-null="true" />
         <generator class="native" />
      </id>
      <set name="BillingInfos" cascade="delete" inverse="true" lazy="true">
         <key column="ProfileId" on-delete="cascade" />
         <one-to-many class="BillingInfo" />
      </set>
   </class>

Code:

  <class name="BillingInfo" table="BillingInfo">      
      <id name="Id">
         <column name="Id" not-null="true" />
         <generator class="native" />
      </id>
      <property name="Primary" column="[Primary]" not-null="true" />
      <many-to-one name="Profile" class="Profile" column="ProfileId" not-null="true" cascade="none" update="false" fetch="select"/>
   </class>

One Profile can have many BillingInfo, but only one of them is the default BillingInfo. The first point (simple one-to-many) is easy to implement.
The question is how to implement the second point, i.e. Profile can have only one BillingInfo.

Thank you in advance.

wolli · **Posted:** Wed Jan 28, 2009 8:42 am

You can use an additional one-to-one association for the default. As an alternative, if you have a field on BillingInfo that indicates the default, you can just define a property and look up the default entry in the BiliingsInfo bag.

v.abramchuk · **Joined:** Fri Jun 20, 2008 8:24 am **Posts:** 7

Thank you for fast response.
Could you post an example, please, of how to implement it via one-to-one? I've already tried it but it wasn't successful (maybe I've done something wrong).

wolli · **Posted:** Wed Jan 28, 2009 9:50 am

Try:

<one-to-one name="DefaultBillingInfo" property-ref="Profile"/>

But have in mind that the DefaultBillingInfo will also be an item in the bag. So probably it will be easier if you put an indicator on BillingInfo or use index 0 as default.

v.abramchuk · **Joined:** Fri Jun 20, 2008 8:24 am **Posts:** 7

I've already tried it, but if there are more then one entities having the same ProfileId (i.e. if there are more then one items corresponding the current profile) NHibernate throws exception saying that there are several entities with the same ProfileId, so, I guess, we cannot map DefaultBillingInfo property in this way without some additional actions (unfortunately, I don't know them).

For now I've solved this issue via implementing it in the following way(not the best solution, but it works):

Code:

      <set name="DefaultBillingInfo" where="[Primary] = 'true'">
         <key column="ProfileId"/>
         <one-to-many class="BillingInfo" />
      </set>

and taking the first item from that set.

I would appreciate a lot if someone show more elegant solution.

Thank you for help.

wolli · **Posted:** Wed Jan 28, 2009 10:38 am

(headbang) ... sorry, my fault ... wasn't thinking thouroughly. Is primary also mapped to your class ? If that's the case, I would use that in the class to get the default item from the set instead of mapping the default.

v.abramchuk · **Joined:** Fri Jun 20, 2008 8:24 am **Posts:** 7

Primary is a property of BillingInfo class and maps the [Primary] column in corresponding table (see mappings in my first post).
As for your last post, I'm sorry but I don't quite see what you mean. Did you mean to iterate through BillingInfos set to find item with Primary set to True?

wolli · **Posted:** Wed Jan 28, 2009 5:27 pm

Yes ... eihter that or always use index 0 for the default.

v.abramchuk · **Joined:** Fri Jun 20, 2008 8:24 am **Posts:** 7

I've implemented DefaultBillingInfo as shown below:

Code:

      <bag name="DefaultBillingInfo" access="field.camelcase" where="[Primary] = 'true'">
         <key column="ProfileId"/>
         <one-to-many class="BillingInfo" />
      </bag>

Code:

      public MemberUserBillingInfo DefaultBillingInfo
      {
         get
         {
            return defaultBillingInfo[0];
         }
         set
         {
            defaultBillingInfo[0] = value;
         }
      }

What I really want is something like that:
http://www.onjava.com/pub/a/onjava/2005 ... tml?page=4

I've tried to implement my DefaultBillingInfo in that way but had no success. Is it possible to do with NHibernate? And if it is I wonder how it may look like.

Thanks in advance.

wolli · **Posted:** Thu Jan 29, 2009 8:20 am

I've never seen this syntac x before. It's probably not yet ported.

v.abramchuk · **Joined:** Fri Jun 20, 2008 8:24 am **Posts:** 7

OK. Thank you for help:)