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timrobertson100
 Post subject: Loosely coupled many-to-many help
PostPosted: Wed Jan 11, 2006 10:42 am 
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Joined: Wed Jun 29, 2005 11:14 pm
Posts: 119
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Hibernate version: 3

Name and version of the database you are using: MySQL 4

I am writing an interface to a legacy database that cannot be changed and have a scenario that I'd appreciate ideas on regarding mappings.

This is simplified but there are 2 tables

Code:
+-------------------------+
|    Scientific_Name      |
+-------------------------+
| Field             | Key |
+-------------------+-----+
| record_id         | PRI |
| name              |     |
| name_code         |     |
+-------------------+-----+

+-------------------------+
|    Common_Name          |
+-------------------------+
| Field             | Key |
+-------------------+-----+
| record_id         | PRI |
| name              |     |
| name_code         |     |
+-------------------+-----+


The join between these tables is the name_code, and thus is a many-to-many join without join tables.

I would like to model this as bidirectional - e.g. CommonName has a Set of ScientificNames and ScientificNames has a Set of CommonNames.

Can anyone help with the mapping for this - can you do joins without using the primary keys?
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timrobertson100
 Post subject:
PostPosted: Thu Jan 12, 2006 4:59 am 
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Maybe I can make this simpler - can I have an object ScientificName that has a Set of CommonName inside it where common name is joined on something other than the ScientificName Primary Key?

If so, how please?
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timrobertson100
 Post subject:
PostPosted: Thu Jan 12, 2006 6:41 am 
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In Hibernate 2.0 I read on the forum I could have used this in the Scientific name so that it didn't use the primary key.

Code:
<set name="commonNames" property-ref="name_code">
   <key column ="name_code"/>
   <one-to-many class="org.gbif.col2005.model.CommonName"/>
</set>


But in 3.0 property-ref is not valid.
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rajasaur
 Post subject:
PostPosted: Thu Jan 12, 2006 7:20 am 
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Joined: Tue Aug 23, 2005 8:52 am
Posts: 181
How about
Code:
<set name="commonNames">
   <key column ="name_code" property-ref="name_code"/>
   <one-to-many class="org.gbif.col2005.model.CommonName"/>
</set>
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timrobertson100
 Post subject:
PostPosted: Thu Jan 12, 2006 7:26 am 
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I was just about to post that after finding it out and spotted your reply - thanks for looking.
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timrobertson100
 Post subject:
PostPosted: Thu Jan 12, 2006 10:04 am 
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Does anyone know why I get "collection is not associated with any session" with the above method? I'm not sure what collections it is referring to as the test I am running does not have any elements in it's collection...
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timrobertson100
 Post subject:
PostPosted: Thu Jan 12, 2006 10:07 am 
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oops - read the rules

[junit] collection is not associated with any session
[junit] org.hibernate.HibernateException: collection is not associated with any session
[junit] at org.hibernate.collection.AbstractPersistentCollection.forceInitialization(AbstractPersistentCollection.java:449)
[junit] at org.hibernate.engine.StatefulPersistenceContext.initializeNonLazyCollections(StatefulPersistenceContext.java:791)
[junit] at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:228)
[junit] at org.hibernate.loader.Loader.doList(Loader.java:2147)
[junit] at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2026)
[junit] at org.hibernate.loader.Loader.list(Loader.java:2021)
[junit] at org.hibernate.loader.criteria.CriteriaLoader.list(CriteriaLoader.java:94)
[junit] at org.hibernate.impl.SessionImpl.list(SessionImpl.java:1483)
[junit] at org.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:298)
[junit] at org.gbif.col2005.dao.impl.hibernate.TaxaDAOImpl.findByRankAndFuzzyName(Unknown Source)
[junit] at org.gbif.col2005.dao.TaxaDAOTest.testGetTaxonByRankAndFuzzyName(Unknown Source)
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rajasaur
 Post subject:
PostPosted: Thu Jan 12, 2006 10:20 am 
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Joined: Tue Aug 23, 2005 8:52 am
Posts: 181
Can you post the relevant code and corresponding mappings ?
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timrobertson100
 Post subject:
PostPosted: Thu Jan 12, 2006 10:41 am 
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Location: København
Scientific name is actually Taxa now...

The query

Code:
from Taxa where taxon=? and lower(name) like lower(?) and recordId>=? order by recordId


The Taxa mapping

Code:
<hibernate-mapping>
   <class name="org.gbif.col2005.model.Taxa" table="taxa">
   
      <id name="recordId" column="record_id" type="long">
         <generator class="native">
         </generator>
      </id>
      
      <property name="taxon" type="java.lang.String" update="true" insert="true"
         column="taxon"/>
      
      <property name="name" type="java.lang.String" update="true" insert="true"
         column="name"/>
      
      <property name="nameCode" type="java.lang.String" update="true"
         insert="true" column="name_code"/>
      
      <set name="commonNames" lazy="false">
         <key column="name_code" property-ref="nameCode"/>
         <one-to-many class="org.gbif.col2005.model.CommonName"/>
      </set>      
   </class>   
</hibernate-mapping>


The common name mapping (The composite key was just because I was playing with another idea)

Code:
<hibernate-mapping>
   <class name="org.gbif.col2005.model.CommonName" table="common_names">
      <composite-id name="key" class="org.gbif.col2005.model.CompositeKey">
         <key-property name="recordId" type="long" column="record_id"/>
         <key-property name="nameCode" type="java.lang.String"
            column="name_code"/>
      </composite-id>
      <property name="commonName" type="java.lang.String" update="true"
         insert="true" column="common_name"/>
      <property name="country" type="java.lang.String" update="true" insert="true"
         column="country"/>
      <property name="language" type="java.lang.String" update="true"
         insert="true" column="language"/>
   </class>
</hibernate-mapping>


This all works for when there is a name_code in the Taxa, but when that is an empty String (legacy DB that can't be changed), there are no common names for this scenario, but that's when I get the exception trace above.

There should be no results to be associated without a session anyways.

Thanks for looking
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