Modeling multiple polymorphic relationships using Hibernate

Ruby on Rails has polymorphic relations which are really useful for implementing functionality such as commenting, tagging and rating to name a few. We can have a comment, tag or rating class which has a many to one polymorphic relationship with a commentable, taggable and rateable object. Also, a given domain object can choose to implement any combination of such relations开发者_运维问答. So, it can for example be commentable, taggable and rateable at the same time.

I couldn't think up of a straightforward way to duplicate this functionality in Hibernate. Ideally, there would be a Comment class which will have a many to one relationship with a Commentable class and a Commentable class will conversely have a one to many relationship with Comments. It will be ideal if the concrete domain classes can inherit from a number of such classes, say Commentable and Taggable. Things seem a little complicated as a Java class can only extend one other class and some code might end up being duplicated across a number of classes.

I wanted to know what are the best practices for modeling such relationships neatly and concisely using Hibernate?

It seems to me that your question is not hibernate specific but more on the lines of "how can I get around the single inheritance model?"

If implementing interfaces is not what you have in mind AOP (Aspect Oriented Programming) might provide a way for you to do what you wish.