Hibernate version:3

I'd like to know if there's a method that will allow me to check if a certain object is cached or not.

Something similar to the method below of the Session:



But I don't want it to pull from the database - just return the cached object (if there IS one) or null perhaps if there isn't.

I'm not even sure how to GET to the cache directly (so thoughts on that might be welcome) or if the id accepted by Session is the same thing used by the cache as it's key - probably not.

But you get the idea right? How can I tell if a certain entity/id is in the cache without forcing it to LOAD the thing (which I do not want to waste time doing).

Thanks!

Havrilesky

You can use session.contains(new YourEntity(theId)), that will return true if the entity is in the session cache.

You can get unrestricted access to EhCache, hibernate doesn't encrypt its cache entries. Have a look at http://ehcache.sourceforge.net/ for the docs.

Well, that didn't seem to work.

I guess the idea is that the Session knows that 2 instances of YourEntity that have the same id property ought to be equivalent?

That makes sense but it doesn't seem to work for me.

(when I try session.getIdentifier(anEntity) I *do* get a string that I recognize as being the ID for that entity)

It's just that when I make a new instance of YourEntity using the same ID for the one I just queried from the database, session.contains returns false.

could this have something to do with the way the id is defined in the .hbm document? (although it seems straight-forward enough to me):



Not sure what to try next. Any advice most welcome!

Havrilesky

There are some restrictions on this that I should have pointed out last time.

session.contains makes use of hashCode, so this trick isn't suitable for entities that correctly define hashCode using a business key. For entities that can't exist in hashed sets, you can use the DB id as the hashCode, and session.contains(new YourObject(youdId)) will work.

For entities with a "good" hashCode, you'll have to find some other way of doing this. Can't think of a solution right now.. you could try session.lock(yourObj, LockMode.NONE) before session.contains(yourObj), but I don't think that'll do it. Worth a shot though.