Probably one of the objects is a proxy and the other is the real
object. It's dangerous to rely on instance equality when proxies
might be present, because it's possible to have several proxies which
refer to the same object.
--
Steve Clark
Technology Applications Team
Natural Resources Research Center/USGS
[EMAIL PROTECTED]
(970)226-9291
Peter> Hi, I stepped over the following problem yesterday. Took us
Peter> half the day to get some understanding of what's going on,
Peter> but we could not figure out how to fix it:
Peter> We have three objects: Order <-> Item <-> Aggregate
Peter> connected with to (bidirectional) 1-to-1 associations. All
Peter> of the associations are configured to be proxies lazily
Peter> loaded on first accessing them. I was starting from an
Peter> Order and navigated to the Aggregate and backwards to the
Peter> Order what resulted in two different instances of the same
Peter> order object (same persistent identity, different Java
Peter> object identity):
Peter> Order order1 = getAnOrderFromSomeWhere();
Peter> Aggregate aggr = order1.getItem().getAggregate();
Peter> Order order2 = aggr.getItem().getOrder();
Peter> // result
Peter> order2.equals(order1) // true
Peter> order2 != order1 // true
Peter> Normally this should never happen, as we use one single
Peter> global ObjectCache (at least this is what I thought how it
Peter> should be). We use the default ObjectCacheDefaultImpl with
Peter> no timeout and autoSync set to false. Objects are never
Peter> removed manually from the cache by our application.
Peter> I see three possibilities (and have one suspect):
Peter> 1) Objects get removed from the cache by the garbage
Peter> collector, when they are only softly reachable. But as I
Peter> have normal references on the first Order object in my app,
Peter> this should not happen.
Peter> 2) Some Identity confusion occurrs. I described a problem
Peter> with different OJB Identities for the same Object
Peter> implementing more than one Interface and thus having more
Peter> than one TopLevelClass. But in this particular case, the
Peter> TopLevelClass of all of my objects is unique and I do not
Peter> see any other reason, why OJB Identities should be mixed
Peter> up.
Peter> 3) Maybe it has to do with the InternalCache used as iterim
Peter> cache by OJB before pushing objects to the real cache. If
Peter> for some reasons, two PersistenceBrokers load the same
Peter> Object at a time, there would be two instances of this
Peter> object in the two internal caches. Only after these objects
Peter> are pushed to the global cache, other PersistenceBroker
Peter> instances would be aware of these objects. As you may
Peter> guess, this is my suspect.
Peter> I do not know exactly when the different objects get
Peter> loaded, as the problem is very hard to reproduce. It just
Peter> occurrs from time to time after working for a while with
Peter> our application.
Peter> Has anybody an idea what really happens and how to
Peter> fix/avoid/work around it?
Peter> Thanks for any help,
Peter> Peter
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