Here is some food for thought: http://db.apache.org/ojb/links.html
;-) Thomas > -----Original Message----- > From: Michael Duffy [mailto:[EMAIL PROTECTED] > Sent: Tuesday, April 01, 2003 6:30 PM > To: OJB Users List; [EMAIL PROTECTED] > Subject: Re: regression test errors > > > > Thank you, Thomas, I think I'll take your advice and > stick with PB API. For some reason, I thought you > intended it as a lower layer API, with ODMG to be > preferred. > > Later in this thread both you and Bonnie referred to > "all the usual suspects" for O/R mapping papers. I've > got copies of Scott Ambler's papers and one by > Wolfgang Keller that is quite good. I've yet to score > a copy of Fowler's architecture patterns book. What > else would you recommend that someone read? What are > the papers "everyone knows" in this area? Thanks in > advance for the education. - MOD > > > --- Thomas Mahler <[EMAIL PROTECTED]> wrote: > > Hi again Michael, > > > > Michael Duffy wrote: > > > Thanks to both Thomas and Armin for their replies > > on > > > this thread. > > > > > > Speaking for myself, I'm nervous about using OJB > > on my > > > current project, too, but I don't think the source > > is > > > entirely OJB. A big part of it is fear of what I > > > DON'T know. I very much liked the idea of using a > > > tool, developed by folks more expert than me. I > > know > > > enought about JDBC to be able to do CRUD > > operations > > > and simple transactions, but the idea of having a > > > layer to abstract all that out of business objects > > was > > > appealing. > > > > > > I heard Martin Fowler talk a few months ago. He > > > mentioned using JAXOR as an O/R mapping tool. > > When I > > > looked into it, I found NO documentation > > whatsoever. > > > > > > Google quickly turned up OJB as an alternative. I > > > liked it right away, because it had more > > documentation > > > than JAXOR, it the cachet of being a Jakarta > > project, > > > and the stuff that I did actually worked. Now > > I've > > > got a tree of four tables linked with m:n > > > associations, all working in JUnit tests. > > > > > > All that's well and good, but now I'm nervous > > about > > > that learning curve and what I'm ignorant of. > > I've > > > done everything with the PersistenceBroker API > > because > > > it was easy to follow in the docs. But now I'm > > > thinking that I should really be doing all of this > > > using ODMG API instead. More learning, with a > > > deadline approaching. > > > > choosing the actual OJB API is an important > > decision. > > > > Why do you think you should use ODMG ? Do you really > > need Object level > > transactions? > > > > If you plan to build your own persistence Manager > > layer with Data Access > > Objects (DAO) (and possibly DTOs) you could be > > better of with the PB API. > > > > The PB API gives you maximum flexibility and nicely > > fits into J2EE based > > programming models. > > > > The ODMG API specification was designed as a > > two-tier rich client API. > > > > > > > > > > Here's a fundamental question: > > > > > > RDBMS developers have put a lot of effort into > > > maintaining referential integrity, managing > > > transactions, etc. It seems to me that OJB is > > taking > > > over a lot of that stuff. When I created my > > tables, I > > > didn't add foreign key constraints. I left all > > that > > > to OJB. The ODMG API will handle true > > transactions > > > and object/row locking. > > > > The OJB/ODMG does have pessimistic object level > > locking. But it does not > > provide DB row level locking! > > > > > > > > But what if OJB isn't the only path into the > > database? > > > A DBA might balk at leaving all those things that > > the > > > RDBMS would handle to OJB. Is it possible still > > leave > > > foreign key constraints in the database so others > > > could use them without OJB? > > > > Yes! It's generally a good idea to let the DB > > maintain data integrity as > > much as possible. OJB was designed to work smoothly > > with existing databases. > > The ODMG transaction manager also takes care not to > > conflict with > > database foreign key constraints. > > > > If you want to sync OJB and non-OJB apps working > > against the same db you > > have to take care of at least two issues: > > 1. Autoincremented Sequence Numbers. The Default OJB > > SequenceManager is > > not aware of external processes. So you have to use > > a SequenceManager > > implementation that uses database managed sequence > > numbers (or > > Identies). There are several such implementations in > > the sequenceManager > > package. > > > > 2. All processes working against the db should use > > optimistic locking to > > avoid data disintegrity. OJB supports OL based on > > Version and timestamp > > columns. > > > > > > > > My compliments to Thomas, Armin, and the team that > > > created OJB. None of this fear is a reflection on > > > your excellent work. It has more to do with the > > fact > > > that this is still a version 1.0 release candidate > > and > > > my own ignorance. Sincerely, MOD > > > > thanks for the compliments, > > cheers > > Thomas > > > > > > > > > > > --- Thomas Mahler <[EMAIL PROTECTED]> wrote: > > > > > >>Hi Bonnie, > > >> > > >>Bonnie MacKellar wrote: > > >> > > >>>I was not at Mobius before 1999, so I really > > would > > >> > > >>not know... > > >> > > >>>Yes, this is for an important project and I am > > not > > >> > > >>feeling > > >> > > >>>very good about this. The alternatives though, > > are > > >> > > >>to buy > > >> > > >>>something or do it ourselves. Our company tends > > to > > >> > > >>be of > > >> > > >>>the "do it yourself" mentality. Since what we > > >> > > >>need is exactly > > >> > > >>>what OJB provides, it seems silly to replicate > > it. > > >>>On the other hand, it is often easier to deal > > with > > >> > > >>bugs > > >> > > >>>in your own code then with bugs in someone else's > > >> > > >>code. > > >> > > >>OJB is 3 years of heavy designed code by experts > > in > > >>the O/R area. > > >>We have a complete regression testsuite that > > covers > > >>each and every > > >>aspect of the system. > > >> > > >>Do it yourself is definitely a bad idea in this > > >>area. If you don't trust > > >>us better use a commercial tool like TopLink. > > >> > > >>OJB is in production use in large projects for 2 > > >>years now. > > >>My company is using OJB in several large and > > mission > > >>critical software > > >>projects since a year now. > > >> > > >> > > >>>I would feel a lot better about this if the mail > > >> > > >>archives > > >> > > >>>worked. My usual approach with this kind of > > system > > >> > > >>is > > >> > > >>>to really sift through user archives, looking for > > >> > > >>similar > > >> > > >>>experiences. > > >> > > >>I admit this is really annoying. But this is > > clearly > > >>not an OJB problem, > > >>but an infrastructure problem with some Apache > > >>server. > > >>For the time being use archive mirrors at GMANE or > > >>at > > >> > > > > > > > > > http://www.mail-archive.com/ojb-user%40db.apache.org/ > > > > > >>cheers, > > >>Thomas > > >> > > >> > > >>>Bonnie > > >>> > > >>>-----Original Message----- > > >>>From: Michael Duffy [mailto:[EMAIL PROTECTED] > > >>>Sent: Friday, March 28, 2003 1:19 PM > > >>>To: OJB Users List > > >>>Subject: RE: regression test errors > > >>> > > >>> > > >>> > > >>>Bonnie, > > >>> > > >>>I'm responding to a note you sent to the OJB > > >> > > >>mailing > > >> > > >>>list. > > >>> > > >>>Is Mobius based in the NYC area? I knew a guy > > >> > > >>named > > >> > > >>>Howard Deiner who worked at a company named > > >> > > >>Mobius. > > >> > > >>>His tenure would have been prior to 1999. Just > > >>>curious. > > >>> > > >>>Also curious - will the system you'll be > > >> > > >>installing > > >> > > >>>OJB into be a large production application? I've > > >> > > >>been > > >> > > >>>getting OJB up and running for a smaller > > >> > > >>production > > >> > > >>>project, and I'm nervous about it. I see all the > > >>>problems on the mailing list and sketchy > > >> > > >>documentation > > >> > > >>>and wonder what I'm getting myself into. JMHO, > > of > > >>>course. Are you feeling the same way? Thanks - > > >> > > >>MOD > > >> > > >>> > > >>>--- Bonnie MacKellar <[EMAIL PROTECTED]> wrote: > > >>> > > >>> > > >>>>Thanks for the advice. > > >>>>This parameter is set in > > >>>> > > >>> > > >>> > > > > > > C:\db-ojb-1.0.rc1\target\test\ojb\repository_database.xml, > > > > > >>>>right? Do I need to change anything else to > > modify > > >>>>this behavior? > > >>>> > > >>>>I'm still trying to feel my way around this > > >>> > > >>system. > > >> > > >>>>Basically, I have > > >>>>about a week to make a recommendation on using > > it, > > >>>>in a large project. > > >>>>Ease of use is an important consideration, > > >>>>especially to the powers-that-be > > >>>>who are managing this project. > > >>>> > > >>>>Bonnie > > >>>> > > >>>>-----Original Message----- > > >>>>From: Armin Waibel > > >>>>[mailto:[EMAIL PROTECTED] > > >>>>Sent: Wednesday, March 26, 2003 6:42 PM > > >>>>To: OJB Users List > > >>>>Subject: Re: regression test errors > > >>>> > > >>>>Seems a problem with the used sequence manager > > >>>>(SequenceManagerHighLowImpl). > > >>>>Try to run the test cases with > > >>>>SequenceManagerInMemoryImpl > > >>>>Do you get the same results? > > >>>> > > >>>> > > >>> > > >>> > > >>> > > > >>>__________________________________________________ > > >>>Do you Yahoo!? > > >>>Yahoo! Platinum - Watch CBS' NCAA March Madness, > > >> > > >>live on your desktop! > > >> > > >>>http://platinum.yahoo.com > > >>> > > >>> > > >> > > > > > > --------------------------------------------------------------------- > > > > > >>>To unsubscribe, e-mail: > > >> > > >>[EMAIL PROTECTED] > > >> > > >>>For additional commands, e-mail: > > >> > > >>[EMAIL PROTECTED] > > >> > > >> > > >> > > >> > > > > > > --------------------------------------------------------------------- > > > > > >>To unsubscribe, e-mail: > > >>[EMAIL PROTECTED] > > >>For additional commands, e-mail: > > >>[EMAIL PROTECTED] > > >> > > > > > > > > > > > > __________________________________________________ > > > Do you Yahoo!? > > > Yahoo! Platinum - Watch CBS' NCAA March Madness, > > live on your desktop! > > > http://platinum.yahoo.com > > > > > > > > > --------------------------------------------------------------------- > > > To unsubscribe, e-mail: > > [EMAIL PROTECTED] > > > For additional commands, e-mail: > > [EMAIL PROTECTED] > > > > > > > > > > > > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: > > [EMAIL PROTECTED] > > For additional commands, e-mail: > > [EMAIL PROTECTED] > > > > > __________________________________________________ > Do you Yahoo!? > Yahoo! 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