question about components and persistence

[gsegura]

Hello, I'm having problems to get same during method invocation, I mean:
there is the class User which has a collection of items.
- One instance of user is maintained during session,
- then there is this action method which adds an item to the user's collection
- there is also another method which ask question about items in the users collection,

the problem is that the user instance is not the same in those methods, so the collection has not the same data. I've tried using merge at the beginning of those methods but an OptimisticLockException is thrown. here is my code so far:

@Scope(ScopeType.CONVERSATION)
@Name("exam")
@Restrict("#{identity.loggedIn}")
public class ExamAction implements Evaluacion {
 //injected from user in session
 @In(required = true)
 @Out
 private User user;


 @End
 public void calificate() {
 //... calculate calification, then:
 Calification cal = user.setCalificacion(course, points) ;

 Calification mergedcal = entityManager.merge(cal) ;
 entityManager.persist(cal) ;
 }

 public boolean isExamDone() {
 // this throws OptimisticLockException, casued by StaleObjectStateException
 //but without this the user (hashcode) is different than the one injected in method calificate
 //so I'm confused :S

 User mergedUser = entityManager.merge(user) ;
 Calification cal = mergedUser.findCalificacion(course) ;
 return cal.getCalificacionEvaluacion()!=null ;
 }
}

@Entity
@Table(name = "user", catalog = "test1")
public class User implements java.io.Serializable {

 @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "user")
 public Set<Calification> getCalificacions() {
 return this.calificacions;
 }

 public void setCalificacions(Set<Calification> calificacions) {
 this.calificacions = calificacions;
 }

 public Calification findCalificacion(Course course) {
 for(Calification c : getCalificacions())
 if(c.getId().getIdCourse()==course.getId())
 return c ;
 throw new NoSuchElementException(
 new StringBuilder(52)
 .append("course ")
 .append(course.getId())
 .append(", not found for user ")
 .append(getId()).toString()) ;
 }

 public Calification setCalificacion(Course course, int points) {
 Calification c = null ;
 try {
 c = findCalificacion(course) ;
 } catch(NoSuchElementException e) {
 c = new Calification(this, course, 0) ;
 getCalificacions().add(c) ;
 }

 c.setPoints(points) ;
 return c ;
 }
}

so the question is, how can I modify the user's collection of items and access same collection every time (I tried outjecting user but no effect) or how can I synchronize those objects before using them?
please, I really appreciate some advice here
regards

[gsegura]

I could, of course, load the user and collection from database every time, but I don't think this is the best way

[pmuir]

This is my preferred solution http://wiki.jboss.org/wiki/Wiki.jsp?page=SeamEntityHomeForLongRunningContexts

[gsegura]

I think I've found the precise answer in last reply of http://www.jboss.com/index.html?module=bb&op=viewtopic&t=103356

the @Out scope doesn't rely on the scope of @In, it must declared individually:
@Out(scope=ScopeType.SESSION)
that's why I wasn't reaching same instance between calls

great forum!

[gsegura]

Thanks for you answer, although I don't see a hit to database at the beginning of every conversation much extra load I would like to know more about why keeping just the Id is better.
At first it would seem to the neophyte like me a more natural way to keep the object itself and perhaps merge it at the beginning of each conversation.
(issue aside I wonder if there is a way to differentiate between a managed entity and one that is not, to avoid the exception thrown when trying to merge an already managed entity)

Rephrasing, when is more appropriate to merge and entity instead of reloading it?
I apologize if this question is not entirely related to seam

[pmuir]

At first it would seem to the neophyte like me a more natural way to keep the object itself and perhaps merge it at the beginning of each conversation.

Thats a valid alternative approach, but doesn't work so nicely with EntityHome.

(issue aside I wonder if there is a way to differentiate between a managed entity and one that is not, to avoid the exception thrown when trying to merge an already managed entity)

entityManager.contains(entity);

Rephrasing, when is more appropriate to merge and entity instead of reloading it?

Both are semantically equivalent in this case AFAICS.