Recommended interface inheritance strategy?

big_main · **Joined:** Wed Jun 29, 2005 12:49 pm **Posts:** 4

I've been toying with many differnet inheritence strategies today, and I was hoping someone could point me to the Right Way to set it up.

I want a way to flag some classes as having a Calendar. It made sense to use an interface, so I called that Schedulable. Now suppose I have Resource, User, and Room that all need a Calendar. The primary keys are very different for Resource/User/Room.

Here are some solutions I came up with:

1. I was thinking of making a unidirectional one-to-one relationship from the three classes to Calendar:

Code:

                 Calendar              
                    ^                    
                    |
            -----------------
           |        |        |
        Resource   User     Room

But then the Calendar can't go back to say the Resource referencing it.

2. I also tried making the Calendar have a relationship with the Schedulable interface:

Code:

   Calendar----Schedulable              
                    |
            -----------------
           |        |        |
        Resource   User     Room

Then the Resource/User/Room need to do something with the schedulable id, but these classes are pretty much unrelated. I don't want the calendarId to be the primary key for any of the classes.

3. Use a discriminator for an association? This doesn't seem to exist by default in hibernate. For instance:

Code:

CALENDAR
---------------
Calendar ID  | Foreign Key | RelationType
 12          |   Jimbo      |  User
 13          |  112         | Resource
 14          |  H114        | Room

Any recommendations?

max · **Posted:** Thu Jul 07, 2005 4:42 am

<any>

big_main · **Joined:** Wed Jun 29, 2005 12:49 pm **Posts:** 4

Is this the recommended way to map it? I only ask because the docs seem to steer people away from using it:

Quote:

It is impossible to specify a foreign key constraint for this kind of association, so this is most certainly not meant as the usual way of mapping (polymorphic) associations. You should use this only in very special cases (eg. audit logs, user session data, etc).