I think this is going to fix a lot of problems I occasionally have. However, I hope the docs reflect the disadvantages of this method, and strenously point out why you shouldn't use it..
I know what kind of developer I am.. Despite my best efforts, if I run into a bug that this would prevent, I'm going to use it, instead of spending the time to fix it properly, and in time, probably just use it everywhere, with the good intention of coming back and removing it later when I get "everything working".. Unfortunantly, we know what road is paved with good intentions... And I'll justify it with the mantra that you shouldn't spend time on performance tuning until you have performance problems. So, while I am happy about having a method to do this, especially for those who run in unusual situations like the Axis example, I'm not sure about the wisdom in giving me a tool to shoot myself in the foot so easily... Eric Pugh > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Gavin > King > Sent: Sunday, November 09, 2003 2:28 PM > To: hibernate list > Subject: [Hibernate] saveOrUpdateCopy() > > > Heres a list of some of the most common problems we get: > > * bad unsaved-value mappings > * problems with cascade save for composite-id classes > * "an object with this id was already associated with the session" > > It turns out that they can all be addressed by adding a new method > to the session. This method looks a little bit like saveOrUpdate() > except that instead of relying completely upon the guess made from > the unsaved-value mapping, it always hits the database to try and > load up the existing object before updating it (or grabs an already > loaded object from the session cache). The new state is then /copied/ > onto the loaded object and the loaded object is returned to the user. > We never get the exception listed above, because we don't try to add > the given object to the cache. If no object is returned from the > database, we save the given object. > > Cascade semantics for this operation are the same as for > saveOrUpdate(). > > This approach has two enormous disadvantages: > > (1) it breaks == from the user's POV > (2) it is much less efficient than just doing an update > > But, as long as we have both options, all is good. > > (Actually, this is a bit of an improved implementation of what has > been proposed for JDO2.) > > Gentlemen, I give you: saveOrUpdateCopy() > > Yes, it is not the most inspired naming ever, but I can't think > of anything better. JDO2 will call this operation reattach() or > reassociate() ... which is an absolutely horrible choice, since > the only thing it does /not/ do is reattach/reassociate the > given instance with the session. (Unlike lock() or update(), > both of which /do/ perform reassociation.) > > This is mainly provided to > > (a) help out people who are trying to make composite-id stuff work > (b) solve problems for people who try to do this: > > Foo foo =.....; > Foo oldFoo = session.get( Foo.class, foo.getId() ); > if (oldFoo!=null) doSomethingWithOldFoo(oldFoo); > session.saveOrUpdate(foo); //ERROR! > > Now they can just happily do: > > Foo foo =.....; > Foo oldFoo = session.get( Foo.class, foo.getId() ); > if (oldFoo!=null) doSomethingWithOldFoo(oldFoo); > foo = session.saveOrUpdateCopy(foo); > > I think this is worth the effort. You can find it in CVS. > > -- > Gavin King > JBoss Group > +61 410534454 > http://hibernate.org > > > > ------------------------------------------------------- > This SF.Net email sponsored by: ApacheCon 2003, > 16-19 November in Las Vegas. Learn firsthand the latest > developments in Apache, PHP, Perl, XML, Java, MySQL, > WebDAV, and more! http://www.apachecon.com/ > _______________________________________________ > hibernate-devel mailing list > [EMAIL PROTECTED] > https://lists.sourceforge.net/lists/listinfo/hibernate-devel ------------------------------------------------------- This SF.Net email sponsored by: ApacheCon 2003, 16-19 November in Las Vegas. Learn firsthand the latest developments in Apache, PHP, Perl, XML, Java, MySQL, WebDAV, and more! http://www.apachecon.com/ _______________________________________________ hibernate-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/hibernate-devel
