ConcurrentModificationException

[bluetrade]

Hi,
I am getting a ConcurrentModificationException which I cannot really resolve, maybe someone has some hints...

I have the following:

@Stateful
@Name("accBroker")
@Scope(CONVERSATION)
@LoggedIn
public class AccountBrokerBean implements AccountBroker{

@In(create=true)
 private EntityManager em;

 @In(value="securityBroker",create=true)
 private SecurityBroker securityBroker;

@In
User user;

 @Begin(join=true)
public void find() {
 List<Accounts> accounts = em.createQuery("from Account");
 securityBroker.filter(user,accounts);

}
...
@Stateful
@Name("securityBroker")
@Scope(CONVERSATION)
@LoggedIn
public class SecurityBrokerBean implements SecurityBroker{

@In(create=true)
 private EntityManager em;

public void filter(User u, Collection<Accounts> accounts) {
 for (Account a : accounts) {
 if (accounts.notAccessibleBy(user) {
 accounts.remove(a);
 } else if (accounts.accessibleBy(user) {
 continue;
 } else {
 accounts.remove(a);
 }
}

}

...

I get the CME somehere in the filter method...
Any clues?

Thanks,
Joey

[bfo81]

You cannot change the length of a Collection (by adding or removing items) while iterating through it.

You can
- make a copy of the account collections, delete accounts from that copy during iteration, clear the account collection and insert all elements of the copy into the account collection *uff*
- insert all accounts to delete into a toDelete collection during iteration, and then iterate over the toDelete collection and delete items from the account collection.

Confused? Here's an example for the second way:

public void filter(...) {
 Collection<Accounts> toDelete = new ArrayList<Accounts>();
 for (Account a: accounts)
 if(accounts.notAccessibleBy(user)
 toDelete.add(a);
 else if (accounts.accessibleBy(user)
 continue;
 else
 toDelete.add(a);

for (Account a: toDelete)
 accounts.remove(a);
}

btw: The checks you make (notAccessiblyBy, accessibleBy) seem to be a bit weird ;). It looks like you want to keep ALL accounts in the collection or delete ALL of them. Wouldn't it work like this?

public void filter(...) {
 if (accounts.notAccessibleBy(user))
 accounts.clear();
}

[bluetrade]

Hi
Thanks for your help.
mhm... I was so sure that it is related to some transactional stuff that I didn't even think about that :) - the first example works...


there are actually a couple of access rules that I left out, so it's quite a complex scheme since accounts have default visibility rules and can be hidden from specific users and can be shared with specific users...

Thanks!!!!