[jboss-user] [Persistence,JBoss/CMP, Hibernate, Database] - 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




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