Mapping a column more than once

jsalvo · **Joined:** Mon Nov 07, 2005 11:10 pm **Posts:** 30

Hibernate version: 3.1.2

The Hibernate on-line reference says:

Quote:

update, insert (optional - defaults to true) : specifies that the mapped columns should be included in SQL UPDATE and/or INSERT statements. Setting both to false allows a pure "derived" property whose value is initialized from some other property that maps to the same colum(s) or by a trigger or other application.

Mapping documents:

Snippet from the Message ( parent ) mapping file:

Code:

      <id name="messageId" type="integer">
         <meta attribute="scope-set">protected</meta>
         <meta attribute="use-in-equals">true</meta>
        <column name="message_id" />
        <generator class="native" />
      </id>
      <set name="notificationHistories" lazy="true" inverse="true" order-by="notified_on desc">
          <key>
              <column name="message_id" not-null="true" />
          </key>
          <one-to-many class="com.mig.connectivity.hibernate.MessageNotificationHistory" />
      </set> 

Snippet from the MessageNotificationHistory ( child ) mapping file:

Code:

      <property name="messageId" type="integer">
          <column name="message_id" not-null="true" />
      </property>
      <many-to-one name="message" lazy="no-proxy" class="com.mig.connectivity.hibernate.Message" insert="false" update="false">
          <column name="message_id" not-null="true" />
      </many-to-one> 

The reason that I want to do this is that ... there are several cases where I already have the id for the foreign key ( obtained elsewhere ... from a legacy system, properties file, or other non-Hibernate means ).

Thus, I don't want to have Hibernate load the parent entity Message every time a new child entity MessageNotificationHistory is being persisted to the database. This means that I don't want Hibernate to do a SELECT on the parent table every time I do an INSERT into the child table. However, that is what Hibernate currently does. There will be times that after loading the child entity, I then want to tell Hibernate to load the parent entity lazily.

So, I tried to map the column twice ... once using a many-to-one to the parent entity, and the second as a normal property as an integer. The on-line reference says this is possible:

Quote:

Setting both to false allows a pure "derived" property whose value is initialized from some other property that maps to the same colum(s)

However, what I get is the stack trace below:

Full stack trace of any exception that occurs:

Code:

org.hibernate.MappingException: Repeated column in mapping for entity: com.mig.connectivity.hibernate.MessageNotificationHistory column: message_id (should be mapped with insert="false" update="false")
        at org.hibernate.mapping.PersistentClass.checkColumnDuplication(PersistentClass.java:575)
        at org.hibernate.mapping.PersistentClass.checkPropertyColumnDuplication(PersistentClass.java:597)
        at org.hibernate.mapping.PersistentClass.checkColumnDuplication(PersistentClass.java:615)
        at org.hibernate.mapping.PersistentClass.validate(PersistentClass.java:405)
        at org.hibernate.mapping.RootClass.validate(RootClass.java:192)
        at org.hibernate.cfg.Configuration.validate(Configuration.java:984)
        at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1169)
        at com.mig.hibernate.HibernateUtil.<clinit>(HibernateUtil.java:32)
        at softgame.gateway.connectors.smpp.AbstractDeliveryReceiptConsumer.saveSubmitResp(AbstractDeliveryReceiptConsumer.java:408)
        at softgame.gateway.connectors.smpp.DeliveryReceiptJMSConsumerImpl.run(DeliveryReceiptJMSConsumerImpl.java:266)
        at java.lang.Thread.run(Thread.java:595)

tenwit · **Joined:** Thu Dec 23, 2004 9:08 pm **Posts:** 2008

Move the insert/update="false" to the proerty, not the many-to-one.

jsalvo · **Joined:** Mon Nov 07, 2005 11:10 pm **Posts:** 30

But I do want to include that integer property in the insert, such that I only specify:

Code:

Integer id = 1234;
MessageNotificationHistory.setMessageId( id ) ;

instead of

Code:

Message msg = session.load( Message.class, someOtherId );
MessageNotificationHistory.setMessage( msg ) ;

I don't want to load the Message entity ( either programatically as above ... or by Hibernate behind the scense ) just to persist a new MessageNotificationHistory entity.

[/code]

tenwit · **Joined:** Thu Dec 23, 2004 9:08 pm **Posts:** 2008

Ah. That will create lots of headaches for you later, seeing a Message will look different after you load it. You should consider changing your mind about this.

Nonetheless it can be done. Your options are:

Change the set to be the "dominant" side of the relationship: remove the inverse="true". Don't both putting the Message into the MessageNotificationHisory, that'll happen automatically when you refresh your Message entity.
Change your many-to-one to not use insert/update=false, but to use <formula> instead of <column>. This tells hibernate that it's a derived property (or relation, in this case), and derived properties are never saved.

jsalvo · **Joined:** Mon Nov 07, 2005 11:10 pm **Posts:** 30

I upgraded to Hibernate 3.1.3. That seems to have fixed the problem without changing the mapping file. Found this in the release notes ( note the bold line that I highlighted ):

Quote:

Changes in version 3.1.3 (2006.03.20)
-------------------------------------------

** Bug
* [HHH-535] - properties element causes exception in interface/abstract class
* [HHH-1236] - Remove static reference to classloader, to avoid memory leak at webapp reload
* [HHH-1248] - explicit joins to collections in subquery result in join conditions being dropped from sql
* [HHH-1287] - Problem with WAS ExtendedJTATransaction not available when using MDB
* [HHH-1325] - ArrayOutOfBounds expected in DatabaseMetadata.isTable when specifing schema
* [HHH-1419] - Update + Exists doesn't seem to work
* [HHH-1433] - many-to-many with additional 'with' join clause generates bad sql
* [HHH-1435] - many-to-one lazy seems to be broken in 3.1.x
* [HHH-1445] - SchemaUpdate closes shared ConnectionProvider
* [HHH-1453] - Broken exception handling in NullableType
* [HHH-1464] - QueryException from Query.getReturnAliases when query uses "fetch"
* [HHH-1486] - Concurrent access issues with both SoftLimitMRUCache and SimpleMRUCache
* [HHH-1489] - mapped composite is is always assumed as transient
* [HHH-1508] - Session.createQuery() should not flush the session
* [HHH-1531] - NPE with many-to-many and property-ref
* [HHH-1546] - generated version properties fail with multiple actions per flush

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