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maciekm
 Post subject: Mapping interfaces and non-polymorphic queries
PostPosted: Thu Feb 02, 2006 11:05 pm 
Newbie

Joined: Thu Feb 02, 2006 10:55 pm
Posts: 3
Hi,

It's been here a million times but always in a different flavour. I've got UserType interface implemented by UserTypeVO. Naturally I would like to map the interface rather than implementation.

I've mapped it kinda successful, but Hibernate forces me to supply a class disciminator, which I have not (there is no inheritance). Is there any way to overcome this?

All I want is the UserTypeVO to be returned in the queries that go on UserType

If don' specify the discriminator I get:

Quote:
org.hibernate.MappingException: No discriminator found for com.eblib.components.business.cemanager.impl.dao.UserTypeVO. Discriminator is needed when 'single-table-per-hiearchy' is used and a class has subclasses


Here's my mapping:

Code:
<hibernate-mapping>
   <class name="com.eblib.components.business.cemanager.UserType" table="EBL_USER_TYPE" lazy="false" select-before-update="true">

      <meta attribute="interface">true</meta>

      <id name="id" column="USER_TYPE_ID" type="java.lang.Long" unsaved-value="null">
         <generator class="hilo">
            <param name="table">EBL_HIBERNATE_KEY</param>
            <param name="column">NEXT_VALUE</param>
         </generator>
      </id>

      <property name="acronym" type="java.lang.String" update="true" insert="true" column="ACRONYM" />

      <property name="active" update="true" type="yes_no" insert="true" column="ACTIVE" />

      <property name="guest" update="true" type="yes_no" insert="true" column="IS_GUEST" />

      <property name="patronType" update="true" type="yes_no" insert="true" column="IS_PATRON_TYPE" />

      <property name="name" type="java.lang.String" update="true" insert="true" column="NAME" />

      <property name="system" type="java.lang.String" update="true" insert="true" column="SYSTEM" />

      <subclass name="com.eblib.components.business.cemanager.impl.dao.UserTypeVO">
         <meta attribute="implements">com.eblib.components.business.cemanager.UserType</meta>
      </subclass>

   </class>

</hibernate-mapping>


Many thanks

Maciej Mastalarczuk
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cfieber
 Post subject:
PostPosted: Mon Feb 20, 2006 1:15 pm 
Newbie

Joined: Mon Feb 20, 2006 1:10 pm
Posts: 1
I ran into the same problem.

My solution was not using the subclass stuff but just create a mapping as if you were mapping the VO directly, but add the entity-name="<your VO interface>"

This seems to work except that when you go to save or saveOrUpdate you need to explicitly pass the interface name with your object:

session.saveOrUpdate(VOInterface.class.getName(), object);


Not sure if this is the correct way of doing it, but it does seem to work.

Mapping an interface instead of a concrete implementation seems less obvious that I had thought it would be.

-Cameron
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treehugger
 Post subject:
PostPosted: Fri Jun 02, 2006 12:31 pm 
How do you use this to do a hibernateTemplate().load()?

I have this:

return (CardHolder) getHibernateTemplate().load(CardHolder.class, id);

where CardHolder is the interface and I mapped it so:

<class name="com.blah.cortex.domain.defaultimpl.DefCardHolder"
entity-name="com.blah.cortex.domain.CardHolder"
table="CRDDET">

and the cast throws a ClassCastException.
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treehugger
 Post subject:
PostPosted: Fri Jun 02, 2006 12:45 pm 
Sorry, ignore me, momentary lapse of concentration.

This does work nicely.

I'd like to know why Cameron is so hesitant about the method though.
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