I'm baffled by this...
I have a class Student. Student has a set, FirstChoices, a set, SecondChoices, and a set, Courses.
All three of these sets are of type Course.

I also have tables Student, Student_FirstChoices, Student_SecondChoices, and Course_Student.

For the *most* part, this goes fairly smoothly; however, when I do an inclusion check to see if the student has a firstchoice that matches the current course (so that I can highlight it) [if(student.getFirstChoices().contains(course))], hibernate appears to be getting mixed up and returning true for courses that are not in the firstchoices set, but *are* in the second choices set.

The debugger shows the course in secondchoices *and* in firstchoices but a select statement in the actual DB shows that the course is in secondchoices exclusively.

A buddy of mine at the office said that it has to do with the fact that I've got the same class referenced three different ways in the hbm file. I don't know if he's correct, but it doesn't seem right. There's nothing out of the ordinary with regards to a sql statement or out-of-bounds with regards to a DB.

Any ideas what could be causing secondchoices to leak into firstchoices? It doesn't seem to leak the other direction, nor does it appear to leak into courses

---snip from Student.hbm.xml--
<pre>
<set name="courses" table="Course_Student" lazy="true">
<key column="student_id"/>
<many-to-many column="course_id" class="org.voight.ats.dto.Course"/>
</set>

<set name="firstChoices" table="Student_Firstchoices" lazy="true">
<key column="student_id"/>
<many-to-many column="course_id" class="org.voight.ats.dto.Course"/>
</set>
<set name="secondChoices" table="Student_Secondchoices" lazy="true">
<key column="student_id"/>
<many-to-many column="course_id" class="org.voight.ats.dto.Course"/>
</set>
</pre>

I have had a similar problem recently when I wanted to multiple sets of the same objects. The problem is that hibernate cannot differentate between objects of which type go in which set.

There two possible solutions to this:

1. add a property to course that tells what type it is

2. extned course into the diffrent types you want and put the type into your mappings

ie:

* @hibernate.discriminator
* column="type"

this way you can still have your two collections but there is away to tell them apart.