Jpa2 entity update problem

[videanuadrian]

Hi All, i develop a app usign spring3 jpa2 hibernate3.x and struts2. I have defined a set of entities for my db tables. I have read about jpa relationships and how to define them, (oneToOne, manyToMany...) and applied this to my app.The problem is that when i update a entity the change is not appwide propagated.
so, i have the following entities :
User
Company
Location
A user is assigned to one or more locations and a company has one or more locations also. So via location i can establish a relation between user and company.

@Entity
@Access(AccessType.PROPERTY)
@Table(name="users")
public class User implements Serializable {

//properties, setters and getters...

 @ManyToMany
    @JoinTable(name="locations_users",
                joinColumns = { @JoinColumn(name="user_id")},
                inverseJoinColumns = {@JoinColumn(name="location_id")}
                )
    public List<Location> getLocations(){
        return this.locations;
    }

    public void addLocation(Location l){
        if (!this.locations.contains(l))
              if (!l.getUsers().contains(this))
                l.addUser(this);
            
            this.locations.add(l);
        }

    public boolean removeLocation(Location l){        
    	if (this.locations.contains(l)){
            if(l.getUsers().contains(this))
                l.removeUser(this);
            this.locations.remove(l);
        }
}

as you can see here when i acess addLocation() or removeLocation() i take care to update the location entity also.
The problem is that after i add/remove a location from a user if i go to the page that list users locations(this time coming from Company->getLocations()->getUser()) the change is not there. I can fix this if i run this.entityManager.refresh() before getting a location for a user. but this is not the behavior that i was expected. As far as i debugged i guess that this location object (entity) has 2 or more instances, and when i update one the other remains obsolete. how do i have to handle this situation ?

PS: my EntityManager is defined as a:

@PersistenceContext(type = PersistenceContextType.EXTENDED,unitName = "PUName")
    protected EntityManager em;

and in applicationCOntext.xml i have defined :

<bean id="txManagerVA"  class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory"  ref="emfVA" />
 </bean>

<bean id="emfVA" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
  <property name="dataSource" ref="vsDS" />  
  <property name="persistenceUnitName" value="PUName"/>
  <property name="persistenceXmlLocation" value="META-INF/persistence.xml" /> 
</bean>

Thanks,
Adrian

[Tolls]

Why are there multiple instances?
Sounds to me like your design is a bit on the odd side here.

[videanuadrian]

i do not know why this behaves like there were multiple instances. Why is my design Odd ?

[Tolls]

Because there probably shouldn't be multiple instances, other than for serving multiple users. In which case I wouldn't expect one to magically update if another one has been updated somewhere else.

Essentially, there is entity A and entity B. Both point to the same data in the database. Each is in its own transaction. B is changed. A still refers to the old data, because that's how transactions work. In isolation.

Now, if you are expecting A to be updated then there is a problem with your design. IMO.

[videanuadrian]

i got your point, it might be very well a design problem because i`m new to jpa. But my understanding is that if as you said i have two entities A and B which refer the same row in one table, and from entity B i update something with persist() and flush() the A would be automatically updated. Or do i have to use refresh() before use ?

[Tolls]

I suspect you'd need to refresh it, otherwise how would it know something behind it had changed? Automatically changing something would break transactional isolation, which is quite important.

I still don't see how you have two of these active at the same time. Are you holding onto them somewhere?
Because I would expect someone going to a page that will display data from that row to get that row fresh from Hibernate/JPA...which would get the updated row.

[videanuadrian]

First of all thanks for the quick replies.
I think that i have to read more about spring transactions and to have a better understanding of these concepts. I`ll come back when have all this clear.
Thanks again.