I am a newbie in Hibernate. I would like to detect if a certain detached entity has been changed (without loading the entity again and comparing field by field) and then make some decision. How can I do this?
Thankyou.

I'm assuming your detached objects are no longer associated with a Hibernate Session, which of course would handle automatic dirty checking. What I've done before is set a boolean flag in each of my object's setters if the value has changed.

private boolean changed = false;
private String firstName;

public void setFirstName(String firstName)
{
setChanged(this.firstName != firstName);
this.firstName = firstName;
}

protected void setChanged(boolean changed)
{
if (changed)
this.changed = changed;
}

I'm not sure of another way to do this without hitting the database again.

Thanks for the reply sneal.

Just pushing it a lil further, is there a built in method in hibernate or a pattern I can use to tell which field in the entity has changed in the detached entity? (In the worst case I would have to read from the database and compare field by field)
Thanks.
Mutahi.

If you want access the database in the worst case you may use select-before-update attribute on the class mapping to tell Hibernate to automatically perform dirty checking and avoid unnecessary update query if detached obect didn't cange or use versioning mechanism support in Hibernate.

Thanks for the reply Lester,
While I like this solution, I still don't get to know which field in the detached entity has changed. Any Ideas?.
Thanks.
Mutahi.