Take a simple example. Student and Course. Many to many relationship.
Student (id, name, ssn, ...)
Course (id, name, ...)

Using hibernate many-to-many does not allow me to store state. So if the join table was StudentCourse(studentid, courseid, dateEnrolled). How can I use the hibernate many-to-many to specify dateEnrolled? From which side(student or course) can i specify state? or do i have to deconstruct the many-to-many relationships into two one-to-many relationship by creating a new object StudentCourse in my domain model?

Can someone please explain how state is stored in many to many relationships?

Thanks.

I'm trying to do the same thing. From my investigation, it seems in this case you do not want Hibernate to automatically generate the StudentCourse intermediary table. It is possible I am incorrect, but I've been searching for a solution to the same question you've posed for the past 3 hours. I think the latter approach you mentioned is correct. You'll have to manually create a StudentCourse class and then do two One to Many mappings.

I can't get this to work using two One to Many relationships to the intermediary table. What would the pk of the intermediary table be? I get a Hibernate error saying the object for the table is missing the pk.

That's because each hibernate entity has to have a PK
Create an id column in the third object

you can also use an combined PK for the relation entity. just use both id's for the primary key, so you do not need to introduce an artificial PK for the relation table. this will also prevent double booking of an student to the same course ;)

greets

So can any experienced hibernate gurus enlighten us on the problems they faced when manually managing a many-to-many relationship as two one-to-many relationships? In terms of search criteria, caching, or other areas? I dont like this, to have to manually manage the mapping.

I had experience with one system where the many-to-many relationship, mapped as an in-between child entity, was actually a one-to-many relationship; furthermore, there was some glitch in the application that caused spurious extra rows (that is, child entities) to be created. For our report queries, we ended up including a subselect:



There are other options besides a child entity and one or two <set> mappings:

* <map> with a component as the key

* use a where=" ... " attribute on the mapping. So say the student_course table is defined as



you should be able to add a mapping

true, but have you thought about a composite element with a nested many-to-one relationship to student?
for example three classes
Course
Enrollment(no id) with dateEnrolled field
Student

where Enrollment is a composite element of Course with a many-to-one relationship to Student.

take a look at the reference 8.2
http://docs.jboss.org/hibernate/stable/ ... nents.html

is this what you want to do?