I am working with a legacy system and am trying to avoid changing the database schema.

This system has two database tables, SurveyChoices and ChoiceGroupItems, which have the same basic schema, except that SurveyChoices contains a foreign key which references a table named SurveyQuestions, while ChoiceGroupItems contains a foreign key which references a table named ChoiceGroup.

I can make this work by declaring Java classes named SurveyChoice and ChoiceGroupItem, and explicitly mapping them to their respective tables and columns. I am wondering if it is somehow possible to not have to declare the member variables in each class and write getters and setters.

I tried Java inheritance - I wrote a class named AbstractChoice and make both SurveyChoice and ChoiceGroupItem extend it. I'm using annotations for my mappings, so I annotated all of the properties in AbstractChoice. I then discovered that annotations in Java aren't inherited, so this didn't work.

I've thought of using an external entity in the XML mapping file to "include" the common definitions in both XML mapping files, but am wondering if there is an easier solution.

I'm relatively new to Hibernate, so maybe there's a way to do this. I think what I'm looking to do is "table per concrete class" without duplicate property/mapping information. Note that these two classes are not ever used polymorphically.

Thanks for any suggestions you might have.

Ryan

In case anyone out there is trying to do the same thing I was, I got this to work using external entities in an XML mapping file. This was suggested in the post at viewtopic.php?f=1&t=930154.

I wrote an XML fragment declaring the common properties in a file called AbstractChoice.hbm.xml. It looks like this:


Then, in the two XML files describing the two classes have the properties above in common, I have the following DOCTYPE declaration:

and then a reference to the external entity common as part of the class element:

Note that the "survey" column is only appropriate for Choice and not the other class that uses the common schema, which is why it is here, rather than in AbstractChoice.hbm.xml.

The hibernate.cfg.xml file referenes only Choice.hbm.xml and ChoiceGroupItem.hbm.xml, not AbstractChoice.hbm.xml.

Finally, there is an abstract Java class named AbstractChoice containing the common properties, and then subclasses that extend AbstractChoice for Choice and ChoiceGroupItem.

I'd still like to do this using annotations, so if anyone has any ideas on how to do that I'd love to hear them.

answer this guy his question. :D he answered mine, he deserves it. ;P