Hibernate 3.0.3

I have a web app upon which I'm using the Long Session pattern.

I load an object foo which has many associated, lazy connections.

Subsequently, the web framework I'm working with sets a number of fields in foo. Since foo is still associated with a session, Hibernate will write through these updates the next time the session flushes.

The problem is, this isn't what I want to happen; I need to do my own validations on the object before I determine if a save should really happen. I want hibernate to actually update the object if, and only if, I call Session.update(foo). Otherwise, I want to be able to manipulate foo to my hearts content without persisting the changes.

To an extent, I can accomplish this if I evict foo as soon as I load it e.g.

Session load(foo, id);
Session.evict(foo)

The problem with this approach though is that later on in the user's life he may, or may not, navigate to a screen which displays a lazy connection. If foo is evicted at that point, I get the infamous lazy initialization exception.

Can anyone suggest an approach whereby I can manipulate a persistent object without either A) having hibernate write through my changes automatically, or B) having to evict my object from the session?

session.setFlushMode(FlushMode.NEVER)

might work for you. See api docs for details.

I looked at that, but I'm not sure I understand precisely what effect it'll have based on the doc.

From what I've seen, if I set FlushMode.NEVER then the session won't flush until and unless I call session.flush().

At such time as I call flush though, *every* pending delta in that session will get pushed through.

Is this the proper mental model? If so, then I'm not sure how that's going to work out for me as it'll require I have an all or nothing flush.

Basically what happens if I have two persistent objects, foo and bar.

Both are dirty.

I want to save foo and only foo. Bar, despite being dirty, shouldn't be saved.

Would FlushMode.NEVER give me that kind of granular control? Or would both foo and bar get flushed when I call session.flush()?

Hmmm, just had a thought...

Could I do this with two sessions?

Something like ...

Session query = SessionFactory.createSession();
query.setFlushMode(FlushMode.NEVER);
Session io = SessionFactory.createSession();

query.load(foo);
query.load(bar);

foo.setSomeProperty(aValue);
bar.setSomeProperty(anotherValue);

io.merge(foo);

Has anyone tried an approach like the above? Can you think of any obvious pitfalls (apart from having to keep two sessions open)?