I am writing a web application which uses hibernate.

I've figured out that it is going to change objects only in a few places which I can handle specially.
In most cases, it would not modify objects during request handling.
In some cases it would modify objects, but I don't want those changes to be persisted - sort of preview mode, I want to change object state, display it for confirmation but don't persist yet.

Here are questions.

How WTFish is using rollback() to cancel changes which I did but don't want to persist? Is rollback() intended to be used only when something really wrong (like exception) occurs, or it can be used just to say "nevermind, forget about it"?

Can I somehow state that I'm not going to make any changes, to skip dirty checks and possibility for some changes to slip in due to some occassional bugs in code?

Can I rollback() transactions which never made any changes to DB instead of committing() them, or that would be a major WTF?

Maybe I should consider anything else here?

I wouldn't play around with roll back since it could and would have side effects. However, you can evict all objects you don't want to be synchronized with database from a session's memory and that will do the trick for you.



Farzad-

Can you be more specific about side-effects I might get?

I would go that evict route, but unfortunately evict doesn't work if object is mapped with natural id. Now I'm considering having those natural-ids removed, remapped as plain properties.

A transaction might be synchronizing multiple resources. In this case your use case may cause other use cases to fail. This is usually a good failure opportunity for a software system that evolves through time. It makes it almost impossible for other developers to respect your decision since transactions have a broader usage.


Farzad-

There are two thing you can also do:

1- Session.clear() removes everything in a session's memory which means nothing will synchronized with database and you don't have to worry about natural ids.

2- You can set Session's flushMode. HB document suggests a MANUAL mode for read only accesses.

I hope either of them do the trick for you.

Farzad-

That "two things" look very heplful. I will surely try them. Thanx for your support.