> > This would sound cool to me too, but from the Cayenne > documentation example, this approach seems to have the > problem that Java has single inheritance :(. > > > > If there's only one such table than it would work > (single inheritance). > > E.g. In the above example, by doing a superclass to > point to the "tag" table(Tag entity), called "Taggable". All > entities that would like to have "tag"s would just need to > extend the "Taggable" entity. > > > > The big problem is how to do it if there are more > tables like that in the scheme :(. > > Yes, you get to have exactly one Tag concept since you can > have only one superclass. Otherwise you have to model this > as an interface, but there is no support for that in > Cayenne. This would have been my first choice too, but I saw no support in Cayenne Modeler for entering additional interfaces - only one super class :(.
> >> Choice 2: > >> Just do exactly what you are doing and fake the > >> relationships. Subclass CayenneContext so that you > can > >> create the appropriate setters and getters to make > this all > >> work. We do this ourselves and I might be able to > dig up > >> some code if you get stuck. > > Are there any examples about this around? > > You could download the onCourse server from our website > (www.ish.com.au/oncourse) and open it up. This looks like a very nice application :). (I haven't seen too many cayenne based applications since some of the links from http://cayenne.apache.org/success-stories.html don't work or they don't point to a download-able application :( ) > Inside there you'll > find our Cayenne model for the application (use version 3 > modeler to look at it). And in there, some tables called > Node and NodeRelation are of interest to you. In the > application itself, we use this to display 'Tags' attached > to lots of different entities: courses, students, etc. > > Here's a snippet of code which then let's you find the > related records. In this Taggable is the interface, Node the > "Tag" entity and NodeRelation the join to other entities. Interesting idea. Thank you very much for the detailed example. I'll try to model like you describe. Joseph.
