Chapter 14.2 from the reference manual states:




My equals and hashCode only uses the the identifier, so there's no need for the proxy to be initialized. Is there a way to tell Hibernate this? Or will Hibernate initialize the proxy anyway for equals() and hashCode() (in which case is this a good candidate for a feature request)?

A class using the database identifier in equals() is possibly broken. See this page (yes, its a mess): http://www.hibernate.org/109.html

Yeah, I've seen that page, along with the looong thread linked at the bottom.

For my application, I'm content to enforce database row equality (hence using the PK in equals()) across the board. Given this, is my original request viable?

Your code is broken anyway if you use the database identifier in equals().

You know, sometimes I just can't figure out if you're trolling or serious. Can you explain why you say this? Obviously I disagree with you here. In fact, the page you pointed out clearly states that this is a viable option:


You may not think this is a good idea, but I can assure you that my code is not broken. It works as I expect it to, and all I'm after now is to see if I can avoid proxy initialization. The proxy problem has discussed at length in http://forum.hibernate.org/viewtopic.php?t=928172, so I know I'm not alone here.

So back to my original question: would it be difficult to tell Hibernate to not initialize a proxy for a class that overrides equals() and hashCode() because it simply uses the PK? I'd imagine this should be simple, but I don't know enough about proxies/cglib to check myself.


Thanks.

Not sure if I can make it any clearer than all the resources you say you have already seen, but here it goes (maybe I can at least make it more condensed):

The issue has to do not so much with the entity itself defining equals/hashCode. Its more a problem of those entities which do define an equals/hashCode being included in a hash-based collection (such as sets and certain map implementations). The contract for those collection interfaces state that the value used to determine placement of the object within the given collection cannot change while the instance is contained in the collection. This is not a Hibernate requirement, these are contracts defined on those standard java collection interfaces; Hibernate simply magnifies it because if you use the db id as the basis for the hash-code (which logic makes the most sense) then you've just broken this contract if the id is assigned to an instance while that instance is included in such a collection.

Visualize what happens when you do this...
1) You load an entity of type A from the session; this entity has a set of entities of type B (assume the Set of Bs is marked with cascade all);
2) You then instantiate a new B and set its values;
3) You add this new B to the loaded A's set of Bs (at this point the Set impl calculates the internal storage position of that newly added B based on the hashCode() method)
4) You flush the session, at which time Hibernate will attempt to save the new B instance through its cascading association to A; here Hibernate or the DB generates the ID value and sets it on the B instance. At this point the contract with the Set interface has just been broken (assuming the hasCode() value is based on the PK).


Hopefully you'll undertand why that above statement is true given the explanation of the issue...


And no, currently there is no way to tell Hibernate to not initialize a proxy on equals() and/or hashCode() invocation.

Use some custom utility:


and "handles" for collections:

It must not be very complicated to implement this custom API.

Steve,

I think you're misunderstanding what I'm asking for. I fully understand the implications of using assigned identifiers. I don't have any problems with equals()/hashCode() and hash-based collections.

My issue is with when Hibernate initializes proxies. Right now, it intializes proxies on equals()/hashCode() invocation only if the persistent object overrides them.

As you noted, there's no way to do so right now.

I'm just wondering how hard it would be to make this user-configurable so that I can tell Hibernate not to initialize a proxy until a persistent property is accessed.