JPA2.0: Delete Entity in OneToMany RelationShip

Question

How do I delete an entity in a OneToMany relationship.

@Entity
@NamedQueries({
   @NamedQuery(name="User.findByUserNamePassword",
     query="select c from User c where c.userName = :userName AND c.password = :password")
})
@Table(name="\"USER\"")
public class User implements Serializable {
    @OneToMany(mappedBy="user", cascade=CascadeType.ALL, orphanRemove=true)
    private List<Profession> professions;

    public List<Profession> getProfessions() {
       return professions;
    }

    public void setProfessions(List<Profession> professions) {
       this.professions = professions;
    }

    public void addProfession(Profession profession){
       if(this.professions == null){
          this.professions = new ArrayList<Profession>();
       }
       this.professions.add(profession);
       profession.setUser(this);
    }

    public void removeProfession(Profession profession){
       if(this.professions != null){
          professions.remove(profession);
          profession.setUser(null);
       }
    }
}

Inside Profession Entity

@Entity
public class Profession implements Serializable {
    @ManyToOne
    @JoinColumn(name="UserId", nullable=false)
    private User user;

    public User getUser() {
       return user;
    }

    public void setUser(User user) {
       this.user = user;
    }

Then inside my EJB I have this

@Stateless
@LocalBean
@TransactionAttribute(TransactionAttributeType.REQUIRED)
public class ScholarEJB{

    /**
     * Add a profession to a target user
     * @param user
     * @param profession
     */
    public void addProfession(User user, Profession profession){
        //Put the user in a managed state. It is important to do this before
        //adding a new profession onto user
        user = find(User.class, user.getId());
        user.addProfession(profession);
        this.create(user);   //This is persist action
    }

    public void removeProfession(User user, Profession profession){
        //Put the user in a managed state. It is important to do this before
        //adding a new profession onto user
        user = find(User.class, user.getId());
        user.remove(user);
        this.update(user);  //merge action
        //this.create(user) //also try this as well, but it does not work
    }
}

Now addProfession work beautifully, but removeProfession does not work. Not sure why? Help please. Do I need to evict caches?

Answer 1

If professions are only part of this relationship, then you can guarantee that when a profession is removed from the User's set it will also be removed from the database by turning on orphanRemoval on the OneToMany side of the relationship.

@OneToMany(mappedBy="user", cascade=CascadeType.ALL, orphanRemoval=true)
private List<Profession> professions;

This is what the JPA 2.0 specification states

The JPA 2.0 specification states that

Associations that are specified as OneToOne or OneToMany support use of the orphanRemoval option. The following behaviors apply when orphanRemoval is in effect:

If an entity that is the target of the relationship is removed from the relationship (by setting the relationship to null or removing the entity from the relationship collection), the remove operation will be applied to the entity being orphaned. The remove operation is applied at the time of the flush operation. The orphanRemoval functionality is intended for entities that are privately "owned" by their parent entity. Portable applications must otherwise not depend upon a specific order of removal, and must not reassign an entity that has been orphaned to another relationship or otherwise attempt to persist it. If the entity being orphaned is a detached, new,or removed entity, the semantics of orphanRemoval do not apply.

If the remove operation is applied to a managed source entity, the remove operation will be cascaded to the relationship target in accordance with the rules of section 3.2.3, (and hence it is not necessary to specify cascade=REMOVE for the relationship)[20].