I'm finding that with a number of hibernate mappings I have a simple version of an entity defined for basic CRUD operations, and then I really need an expanded version of the same entity that includes all of its associations for reporting process optimization.

For example: I have an entity (e.g. course) that has a number of related sub entities (e.g. attendees, class times etc) but I don't want to include these sub entities as properties in the main entity class structure.

To get around this I'm using the following class hierarchy...


Now for all entity level CRUD operations I'm using 'Course' and 'Attendee' separately to add entries to the underlying database. However, for reporting purposes I want to use 'CoursePlusBookings, which allows me to show a list of courses with the number of bookings.

Now the only way I can find to support this approach is to have two separate mappings - one for 'Course' and a second for 'CoursePlusBookings' - both of which map to the same table. I can't find a way of implementing mapping inheritance to avoid this duplication. I did raise this question sometime ago (see viewtopic.php?f=1&t=984333) but unfortunately the respondents misunderstood my question, so I'm asking it again.

I suppose in a way this posting boils down to a question about whether it is possible to have mapping element associations that are read only in nature. In otherwords if persisted CoursePlusBookings then the Attendee set would not be persisted as part of that operation.

Or is there another way to achieve what I'm after?

Hi davout_uk,
after looking at the cross post, and all big shot guys trying to answer.. I dont know how much i will be helpful. But I did went through this scenario and here are my 2cents.
This is what I had to do assuming similar scenarios like yours. There is no mapping needed for the Reporting Entity CoursePlusBookings it will be a stand alone POJO to hold data.
CoursePlusBookings will look something like this:-
public CoursePlusBookings extends AbstractCourse {
//dont know how the AttendeeID is mapped to the database so make the data type as java.lang.Number instead of int.
private int AttendeeID;
//optional.
//private int CourseID;
private String StudentName;
//And the set too to make you wonder why we need this..
private Set<Attendee> Attendees;
...
}
Write a SQL query that would return the data that you need for the reporting purposes. And the data would be returned something like this:-
CourseID Title Teacher AttendeeID StudentName
1 java mark 10 student1
1 java mark 11 student2
2 advjava brad 12 student3
2 advjava brad 13 student4
// unfortunately transformers do not do a compareTo operation on the POJO's defined even if they have an implementation.
List<CoursePlusBookings> objects = HibernateUtil.getSession().createSQLQuery(<<your query here>>).setResultTransformer(
Transformers.aliasToBean(CoursePlusBookings.class)).list();

your list of CoursePlusBookings will have the data as returned in the query results. Use some kind of logic to shrink the data to fit into what you need. I can post the logic too but before that want to make sure this is what you want.

Hope this helps,
-Srilatha.

Thanks for the reply, but it looks like I'll have to stick with the duplicate mapping solution.

In the meantime I've posted an enhancement request to address this area.

Another idea...

Is there a way to make the sets read only? In that the sets are not included in any INSERT or UPDATE actions.