I know this seems impossible but is there a way to check if an object matches a Criteria without hitting the database?

Something like boolean objectMatches = criteria.matches(someObj)

If and only if you know the object is in one of the caches. Otherwise, you're asking, as you said, the impossible.

Can you tell me the price of Google stock without looking, assuming you didn't look a few moments ago?

I wondered the same thing about if it was in the cache. But given the example:

Cat cat1 = session.save(new Cat("snowball",120));

Cat cat2 = session.createCriteria(Cat.class)
.add( Restrictions.like("name", "snow%") )
.add( Restrictions.gt( "weight", new Float(100) ) )
.uniqueResult();

Is it possible that cat2 will be equal to cat1 without hitting the database, if all field comparisons are done in the database (no id is available)?

Re: Can you tell me the price of Google stock without looking, assuming you didn't look a few moments ago?

If I always know the price of google stock before it's saved in the DB.

I'm basically trying to take advantage of the power of the Criterion API. To determine if an object meets a criteria.[/i]

If you are asking whether



would be true, then yes, I believe so, assuming you even get to this point (given the criteria, it is quite possible .uniqueResult() doesn't make sense... there could be a cat named "snowy" that's 130 lbs.)

However, if you are asking if this would avoid a database hit when you ran the criteria, then, no. I'm fairly certain you would end up with the expected database call for the criteria. After all, hibernate itself will need to check to see if any other Cats meet the criteria.

In any case, if I understand what you're trying to do, it's probably a bad use of the criteria API. Criteria is meant for searching the database, so executing a criteria with the hopes it won't hit the database is generally a conflict of interests. A limited exception to this is cached queries, but note that the query cache does not (at least according to Hibernate in Action) cache entities, only entity identifiers and non-entity values.

Actually I could have made my example better I should have said:

Cat cat1 = session.save(new Cat("snowball",120));

boolean catMatches = session.createCriteria(Cat.class)
.add( Restrictions.like("name", "snow%") )
.add( Restrictions.gt( "weight", new Float(100) ) )
.matches(cat1);

and catMatches would be true.

I'm thinking a translation could be done such the logic would be:

catMatches = cat1.name.matches("snow*") && cat1.weight > 100.0;

Of course this is a simplistic example and a full implementation of all the Criteria API capabilities would not be possible without hitting the DB.

If I think I understand what you are saying about cached queries it would only help if I knew the id ahead of time and had saved it.

Thanks for the comments though... I'll be sure and rate your posts helpful.