[OJB-developers] Performance improvements with Identity objects

[Florian B. <bf...@fl...>]

Hi,

while fixing the referential integrity issue in the ODMG layer I found that
Identity objects are instantiated over and over again. Instantiating objects
is one of the most expensive operations one can do in Java, first it creates
a lot overhead when instantiating such classes, then it adds overhead in the
garbage collector.

Once an Identity object is created, the chances it will change is very
little. Why not store the Identity object, once it is created? VirtualProxy
and IndirectionHandler already do this, if you create an Identity the
content of the stored Identity is copied. If we added such storing
capabilities for normal objects to a, lets say, IdentityFactory, in most
cases a new instantiation could be avoided.

If an Identity object is requested from IdentityFactory, it should first
check whether for the given object an Identity exists. If yes in a second
step it should be checked if the key values have changed. If yes, create a
new Identity (because Identity should be immutable, imho, so they could
still be used in HashMaps), if no just return the already existing object.

Most critical for design and implementation is in my opinion avoiding memory
leaks. But I think this could be handled with WeakReference and friends.

Any comments?

lG,
Florian