How to delete relations in entities, id´s are not the

[nschweig]

Hi,

I have a webapplication with jsf and ejb.If I try to delete relations between entities I always run into the same problem. The id of the objects are not the same so I can delete them from the list.

For example:
Relation Course/CmtUser

Course.java

@ManyToMany(fetch=FetchType.EAGER)
@IndexColumn(name="INDEX_COL")
private List<CmtUser> participants = new ArrayList<CmtUser>();

CmtUser.java

@ManyToMany(mappedBy="members", fetch=FetchType.EAGER)
@IndexColumn(name="INDEX_COL")
private List <CmtGroup> groups = new ArrayList<CmtGroup>();

Joining a course is not the problem:

JSF-managedbean CourseBean:

public void joinCourse(){
 currentUser = userHandler.getCmtUserByUserName(getRemoteUserName());
courseHandler.joinCourse(getCurrentCourseId(),currentUser);
}

But if I try to "leave a course" (delete user from course-participant-list) it does not work.
I tried it in several ways:
1. Way
The managedbean CourseBean invokes the handler and gives the objects to it:

public void leaveCourse(){
courseHandler.leaveCourse(currentCourse, currentUser);
}

Then in the handler I tried to remove the user from the course and vice versa

public void leaveCourse(Course c, CmtUser user) {
 c.getParticipants().remove(user);
 user.getCourses().remove(c);
 em.merge(c);
 em.merge(user);
 }

Problem: Cannot remove the user from c. participants because the id from the user I not the same as the user in the list participants.

The same problem in the 2. Way

2. Way
The managedbean CourseBean invokes the handler:

public void leaveCourse(){
courseHandler.leaveCourse(currentCourse.getId(), currentUser.getId());
}

CourseHandler.java

public void leaveCourse(Long courseId, Long userId) {
 Course course = getCourse(courseId);
 CmtUser user = userHandler.getCmtUser(userId);

 course.getParticipants().remove(user);
 user.getCourses().remove(course);
 em.merge(user);
 em.merge(course);
}

If I look into course.participants the id from the user in it is another than the id from the user I got with my userHandler with userHandler.getCmtUser(userId);.

3. Way:

I remove the elements from the list in the jsfmanagedbean CourseBean:

public void leaveCourse(){
 currentCourse.getParticipants().remove(currentUser);
 currentUser.getCourses().remove(currentCourse);
 courseHandler.updateCourse(currentCourse);
 userHandler.updateUser(currentUser);
}

The only thing I do in the ejbhandler is to update the objects:
CourseHandler.java

public void updateCourse(Course course) {
 em.merge(course);
}

UserHandler.java

public void updateUser(CmtUser cmtUser) {
 em.merge(cmtUser);
}

But it is the same problem.

How do I solve this? Which is the best way to implement this things; in the jsfmanagedbean or in the ejbhandlers?

Please I need your help.

Thanks Nicki

[nschweig]

Needed to override equals() and hashCode().