Hi all,

Is it possible to have a client (a session bean) handling this kind of relationship transparently when an attribute is associated to the relation?

Here is a comprehensive description of the issue:


Data Model
----------

  -------------------
 ¦ STUDENT ¦
 ¦ - student_id (pk) ¦
 ¦ - name ¦
 ¦ ¦
  -------------------
           ¦1
           ¦
           ¦
           ¦
           ¦n
  -------------------
 ¦ GRADE ¦
 ¦ - course_id (fk) ¦
 ¦ - student_id (fk) ¦
 ¦ - grade (integer) ¦ <-- this is the issue
  -------------------
           ¦n
           ¦
           ¦
           ¦
           ¦1
  ------------------
 ¦ COURSE ¦
 ¦ - course_id (pk) ¦
 ¦ - code ¦
 ¦ ¦
  ------------------
  
Is it possible to map this to a N-M relationship between a Student class and a Course class?
The answer is usually yes, but this time the "grade" attribute causes me a lot of trouble.

Is it possible to do something like:

student.getCourses().add(course,8)

with 8 being the grade for this course and this student?

The idea is that a call to the add() method would trigger an insert of a new row in the 'GRADE' table. getCourses() could return a Map, with a Course as key and an Integer (the grade) as value.

If, as it seems, this is not possible in a simple declarative way, we would then fully promote GRADE as a plain EJB, and have two 1-N relationships, but I would like to hide the 'Grade' entity inside the Java code.

Thanks for your help,

Chris.

I'd prefer to keep the Course and Student entities grade agnostic, and introduce a GradeController SLSB that manipulates the Grade table directly. What I'm wary of is introducing "simple" relationship accessors into an entity that:
- would then share responsibility for the CRUD of the grade with another entity in the association
- might easily develop its own business rules (e.g. notification if a grade is changed)