Hi Noah,
I saw your suggestion, currently that is above and beyond what is
outlined in the JPA spec. Feel free to log an enhancement request
though against EclipseLink.
As for the default, I can't speak to all the decisions of the JPA
spec committee, but could be in this case that it is valid to not
sort some items and have them appended at the end of the list by
setting them to null.
Cheers,
Guy
On 07/06/2012 1:01 PM, Noah White wrote:
Hi Guy,
That's unfortunately what I am going to have to do in this
case (see my suggestion to the list about EclipseLink using a
LinkedHashSet when it sees @OrderColumn applied to a Set).
BTW, I am surprised that the default value of 'nullable' is
true for @OrderColumn. Why would this column ever contain a
NULL?
-Noah
On Jun 7, 2012, at 10:47 AM, Guy Pelletier wrote:
Hi
Noah,
Likely not ideal, but you could change your model to use
a List with OrderColumn and when adding a favorite
desert you'll have to check the List if it already
exists.
Cheers,
Guy
On 07/06/2012 10:36 AM, Noah White wrote:
On Jun 7, 2012, at 7:45 AM, Guy Pelletier wrote:
Hi Noah,
Yes, the use of an OrderColumn is currently
intended to be used with a List only. You can
however use the JPA OrderBy annotation instead
which can be used with a Set.
Cheers,
Guy
Hi Guy,
Thanks for your feedback. The rub with the @OrderBy
approach is it relies on a column in the related
entity, however, I want/need to enforce an ordering on
the the relationship. Some pseudo code to illustrate:
public class Diner {
@ManyToMany
@JoinTable(...)
Set<Dessert>
favoriteDesserts;
get/set
favoriteDesserts
}
public class Dessert {
@ManyToMany(mappedBy="favoriteDesserts")
Set<Diner>
favoritedBy;
}
I want to preserve the order that a Dessert is
added to the favoriteDesserts. I also want to enforce
that the Set of favorite desserts does not contain
duplicates. There is no particular property of
Dessert to indicate an favorited order since the
favorited order should be part of the join table as it
relates to that and is not unique to an instance of
Dessert which is why @OrderBy isn't really going to
help.
-Noah
On 06/06/2012
5:52 PM, Noah White wrote:
I was reading over the docs [1] regarding
Eclipselink's support for @OrderColumn. It
looks like this only applies to List and not
Set. The reason I ask is because I have a
ManyToMany bi-directional relationship (using
a join table) which is a Set and is
implemented with a HashSet because the
collection can't have duplicates.
I wanted to order the entries in this set
using @OrderColumn, but it appears I can only
apply this to List, however using List will
break my unique requirement. Is this
understanding correct?
If so what is the recommended strategy for
this case?
Thanks,
-Noah
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