Re: [eclipselink-users] OneToMany list insert problem

[Renee Revis <renee@xxxxxxxxxxxxxxx>]

Hi James,

I showed the actual remove in a later message and then, trying to find a temporary workaround, the difference between a remove and a get.  The remove case fails, the get is ok, so it seems to be a remove problem.

The other messages explain in more detail what I'm seeing in the cache in relation to the transactions and the elements that are there/not there.

I am using an OrderBy annotation.  Isn't that the same thing as an OrderColumn?

I'll try changing the EAGER to LAZY to see if it makes a difference.

Renee


On Feb 29, 2012, at 11:16 AM, James Sutherland wrote:

> 
> I don't see in your code where you remove the element from the list?
> 
> In general, since you are removing and adding to the list, you basically did
> not change the relationship, so I would expect no changes at all, it is very
> odd that the element is removed in the cache, was it there to begin with? 
> Ensure that you are maintain both sides of the relationship in general.
> 
> I don't think changes to order are seen as changes unless you use an
> OrderColumn, so you could try using that.
> 
> EclipseLink has two modes of change tracking, one through events, and the
> other through cloning.  Because you relationship is EAGER it is using the
> cloning method.  You could try setting it to LAZY, to see if this is related
> to the DEFERRED change tracking.
> 
> 
> 
> 
> drrevis wrote:
>> 
>> 
>> I have a bi-directional ManyToOne mapping between two entities.  I
>> maintain the order of the list on the OneToMany side based on a ranking
>> field.  Initially I can create the entities and everything is fine.  After
>> that, when I use a question line, I remove it from the list, update the
>> ranking and then add it back into the list based on the new ranking value. 
>> I realize that the ManyToOne side is the owning side and it's up to me to
>> maintain the list order in memory, and that's what I'm trying to do.
>> 
>> Everything seems to work fine at first.  Just before the EJB transaction
>> finishes, I log the elements of the list and everything is as I expect. 
>> However, when I make the next request (i.e., a new EJB transaction),  the
>> list shows that the element was removed from the list, but never added
>> back in.  This doesn't match what it previously showed, however, in the
>> first EJB transaction context.
>> 
>> If I query the elements that are actually in the database, all of the
>> elements are still there.  And if I restart the server to force everything
>> to be restored from the database, it all comes back as I expected (i.e.,
>> with the element in the list and ordered as I expected), so it seems to be
>> a caching issue somehow with the persistence context.  
>> 
>> Does anyone have any ideas as to what might be causing this problem and
>> how to add the element back into the list correctly?  I've tried a variety
>> of things, and nothing has worked so far.
>> 
>> Thanks for any help,
>> Renee
>> 
>> 
>> 
>> The relevant parts of the entities are:
>> 
>> public class UserSelectorQuestionLine implements Serializable {
>>    private Integer ranking;
>>    @ManyToOne
>>    private UserSelectorQuestionGroup questionGroup; 
>> }
>> 
>> and
>> 
>> public class UserSelectorQuestionGroup implements Serializable {
>>    @OrderBy("ranking ASC")
>>    @OneToMany(fetch=FetchType.EAGER, mappedBy="questionGroup")
>>    private List<UserSelectorQuestionLine> questionLines;
>> }
>> 
>> 
>> And the routine I use to add an element into the list  in the
>> UserSelectorQuestionGroup class is:
>> 
>> public void addUserSelectorQuestionLine(UserSelectorQuestionLine
>> newUserSelectorQuestionLine) {
>>    int index=0;
>>    Random gen = new Random();
>> 
>>    if (this.questionLines.size() == 0) {
>>        this.questionLines.add(newUserSelectorQuestionLine);
>>    } else {
>>        for (UserSelectorQuestionLine nextQuestionLine :
>> this.questionLines) {
>>            if (newUserSelectorQuestionLine.getRanking() <
>> nextQuestionLine.getRanking()) {
>>                break;
>>            } else if
>> (newUserSelectorQuestionLine.getRanking().equals(nextQuestionLine.getRanking()))
>> {
>>                // We want to mix up the order of the question lines that
>> have equal ranking
>>                if (gen.nextInt(2) == 1) {
>>                    break;
>>                }
>>            }
>>            index++;
>>        }
>>        this.questionLines.add(index, newUserSelectorQuestionLine);
>>    }
>>    this.minRanking = questionLines.get(0).getRanking();
>> }
>> 
>> I know this routine is called and is working correctly because I can
>> display the elements of the list after this is called and everything is as
>> expected in the first EJB transaction context.
>> 
>> 
>> 
> 
> 
> -----
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