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From "LAURENT Stephane" ...@adequates.com>
Subject Re: Queries for M:N collections?
Date Thu, 02 Oct 2003 09:11:25 GMT
Hi,
I'm not sur to understand, but ...
you have :
Class A
{
    Integer idA;    
    String attribute1_A;
    String attribute2_A;
...
    Collection listOfA
}


if your repository is like this :
<class-descriptor class="A" table="tableA">
        <field-descriptor name="idA" column="ID" jdbc-type="BIGINT" primarykey="true" autoincrement="true"/>
        <field-descriptor  name="attribute1_A" column="a1" jdbc-type="VARCHAR"/>
        <field-descriptor name="attribute2_A" column="a2" jdbc-type="VARCHAR"/>
...
        <collection-descriptor name="listOfA" element-class-ref="A" auto-retrieve="true"
auto-update="true" indirection-table="tableA_A">
            <fk-pointing-to-this-class column="idA"/>
            <fk-pointing-to-element-class column="idA"/>
           </collection-descriptor>
  </class-descriptor>


you can getCollection of A where listOfA contain at lesat one element equal to wantedAInstance
:

crit.addEqual("listOfA",wantedAInstance);
getCollectionbyCriteria(A.class,crit);

you can getCollection of A where listOfA contain at lesat one element A having at least A
in his listOfA collection :

crit.addEqual("listOfA.listOfA",wantedAInstance);
getCollectionbyCriteria(A.class,crit);

...

is it your goal ?
  ----- Original Message ----- 
  From: Joe Germuska 
  To: OJB Users List 
  Sent: Thursday, October 02, 2003 12:00 AM
  Subject: Queries for M:N collections?


  At 16:44 -0500 10/1/03, Joe Germuska wrote:
  >I'm dealing with a case where I want to model an M:N relationship 
  >between two objects of the same type.  I have a collection 
  >descriptor modeled off of the example for this on the OJB site. 
  >When I go to store, I'm getting a class cast exception...

  For what it's worth, changing that property to a Collection 
  definitely solved my problem.  Which leads me to the real question:

  I need to construct a Query which selects collections for either 
  direction of this relationship.  That is, Given a parent, I need to 
  find all of its children, and given a child, I need to find all of 
  their possible parents.

  I can probably work this out with a QueryBySQL, but I'm trying to 
  avoid that.  I don't see any methods on Criteria to set where I can 
  set something like "property contains some member"...  Can anyone 
  advise?

  Thanks in advance,
  Joe

  -- 
  Joe Germuska            
  Joe@Germuska.com  
  http://blog.germuska.com    
    "We want beef in dessert if we can get it there."
     -- Betty Hogan, Director of New Product Development, National 
  Cattlemen's Beef Association


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