Hi Charles, Thanks for the detailed answer. That does the job nicely. We had moved from an m:n relationship and were somewhat blinded by the fact that we hadn't been using the association table directly (we had used it as an 'indirection-table').
Thanks again, John -----Original Message----- From: Charles Anthony [mailto:[EMAIL PROTECTED] Sent: 04 March 2003 16:46 To: 'OJB Users List' Subject: RE: Ternary associations Hi, OK, I think I understand what you want. Why is this a "special" scenario ? You can (and we have in our app) defined a class that represents the relationship. We have mapped that to a table with the corresponding ids. We can then do queries/updates on that relationship as with any other. Here's an example : it's worked entirely in the email and is probably too brief, so it doesn't compile and probably has errors. However, it should illustrate that it is possible with OJB. java class : public class ProjectRelationship { Integer developerId; Integer languageId; Integer projectId; Developer developer; Language lanuage; Project project; /** Normal setters and getters **/ } extract from the repository : <class-descriptor class="ProjectRelationship" table="PROJECTRELATIONSHIP"> <field-descriptor id="1" name="developerId" column="DEVELOPER_ID" jdbc-type="INTEGER" /> <field-descriptor id="2" name="languageId" column="LANGUAGE_ID" jdbc-type="INTEGER" /> <field-descriptor id="3" name="projectId" column="PROJECT_ID" jdbc-type="INTEGER" /> <reference-descriptor name="developer" class-ref="Developer"> <foreignkey field-id-ref="1" /> </reference-descriptor> <reference-descriptor name="language" class-ref="Language"> <foreignkey field-id-ref="2" /> </reference-descriptor> <reference-descriptor name="project" class-ref="Project"> <foreignkey field-id-ref="3" /> </reference-descriptor> </class-descriptor> storing a relationship : Developer d = .... (create or retrieve); Project p = .... (create or retrieve); Language l = .... (create or retrieve); ProjectRelationship r = new ProjectRelationship(); r.setDeveloper(dev); r.setLanguage(l); r.setProject(p); Broker.store(r); querying for all relationships that developer 'bob' has in 'java' : Criteria criteria = new Criteria(); criteria.addEqualTo("developer.name","bob"); cirteria.addEquatTo("language.name","java"); Query q = new QueryByCriteria(ProjectRelationship.class, criteria, true); Collection relationships = Broker.getCollectionByQuery(q); You can then iterate through the relationships to get the projects. You could also have on the Project class-descriptor a <collection-descriptor> that returns all relationships associated with the Project. If it was call "projectRelationships" the following would give you all projects that have a relationship with "bob" and the language "java". Criteria criteria = new Criteria(); criteria.addEqualTo("projectRelationships.developer.name","bob"); cirteria.addEquatTo("projectRelationships.language.name","java"); Query q = new QueryByCriteria(Project.class, criteria, true); Collection projects = Broker.getCollectionByQuery(q); Hope that helps , Cheers, Charles. >-----Original Message----- >From: O'Reilly John [mailto:[EMAIL PROTECTED] >Sent: 04 March 2003 16:22 >To: 'OJB Users List' >Subject: RE: Ternary associations > > >Hi, > >With a ternary relationship there are three (or more) objects >'related' to >each other. An example would be 'developer', 'language', >'project'. You >want to represent the combinations of these that exist. It's >realised by a >bridge table with 3 columns representing the foreign keys in >the other 3 >tables (just like an m:n association is represented by a table with 2 >columns). > >The following explains how hibernate supports ternary associations. >http://www.xylax.net/hibernate/ternary.html > >Regards, >John > >-----Original Message----- >From: Charles Anthony [mailto:[EMAIL PROTECTED] >Sent: 04 March 2003 16:08 >To: 'OJB Users List' >Subject: RE: Ternary associations > > >I didn't know exactly what a Ternary association is. >A quick google suggests that it is what OJB calls an M:N association (a >resolution for a many-many relationship). > >If it is one of them, then yes, OJB does support it. > >See >http://db.apache.org/ojb/tutorial3.html#mapping%20m:n%20associations > >Cheers, > >Charles. > >>-----Original Message----- >>From: O'Reilly John [mailto:[EMAIL PROTECTED] >>Sent: 04 March 2003 15:58 >>To: 'OJB Users List' >>Subject: RE: Ternary associations >> >> >>Hi, >> >>Sorry to repost the following question but can someone give >me a yes/no >>answer on this. If no, then we need to look for another way >>of doing this. >> >>Thanks, >>John >> >> >>-----Original Message----- >>From: O'Reilly John [mailto:[EMAIL PROTECTED] >>Sent: 26 February 2003 16:59 >>To: 'OJB Users List' >>Subject: Ternary associations >> >> >>Hi, >> >>According to the following, OJB is supposed to support ternary >>associations: >>http://c2.com/cgi-bin/wiki?ObjectRelationalToolComparison >> >>I can't find any info on this. 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