With OJB the JDO implementation is Abstracted over the top of their base Persistence classes. So it is an abstraction of an abstraction. Personally, I never used the JDO. So, I would not be the best to inform you about OJB's implementation of JDO.
All of the prior information I gave you is still valid. I know that the OJB community is pretty honest about the performance trade-off when you use OJB's ODMG or JDO implementation. You should probably move this thread over to them and ask them. Personally, I get a bit nervous about the overhead that can be created using a system like this. Especially when it comes to caching. Say you load a Category Object and that Category contains 500 items and those 500 items contain on the average of 20 bullet points. If you are not careful about how you are coding it you will have 500 Category objects cached in memory along with all of it's nested objects. That is a lot of overhead to be storing in a cache. Like I said earlier, the caching is all or none. When loading objects you may find that if you don't eliminate the cache you wind up with old data in other parts of your app. For example you have a list of users. When you view that list you initially see all of your users. But, if you add a new user and your struts app then forwards back to that user list, without wiping out the WHOLE OJB cache, then your new user will not show up in the list. Rather, OJB will retrieve the cached version. I wound up turning off the cache. But then my performance went in the toilet. DISCLAIMER: I stopped using OJB at 0.9.7 so they may have added better caching. The base of OJB is the Persistence classes which I would reccomend you get familiar with in order to understand the base nature of OJB.The JDO implementation uses those classes to implement JDO. I would start inquiring at the OJB mailing list to get more accurate and updated information. Brandon Goodin Phase Web and Multimedia P (406) 862-2245 F (406) 862-0354 [EMAIL PROTECTED] http://www.phase.ws -----Original Message----- From: Dan Tran [mailto:[EMAIL PROTECTED]] Sent: Saturday, January 25, 2003 12:57 PM To: Struts Users Mailing List Subject: Re: Struts and OJB I am investigating quite a few object mapping frameworks and JDO seems to be my only choice to stick with. Is it a good assumption since it is a standard framework? -Dan ----- Original Message ----- From: "Brandon Goodin" <[EMAIL PROTECTED]> To: "Struts Users Mailing List" <[EMAIL PROTECTED]> Sent: Saturday, January 25, 2003 10:30 AM Subject: RE: Struts and OJB > I have used OJB in two project. Be sure you know the performance impact. It > is a great tool. But, it will take you a while to learn how to use it > "effectively". The caching is all or none (you can spin your own) and the > fine grained control that you have over object materialization is something > you need to understand. I would say for you to make sure you understand how > to use the Proxy. If you don't you will be creating massive amounts of > objects and slow your performance drastically. IMHO, I don't think that OJB > is the answer for all projects. The reduction that you find in your own code > as compared to the time it takes to become completely familiar with an > evolving code base is pretty dramatic. Like mentioned earlier. I think that > after a 1.0 final version is released then the community will have more time > to update the docs and write some books. When that happens I am going to > take another look at it. Until then... I just can't keep up and I don't > think that it is performant for the "ignorant" (i.e. me :-)) All I can say > is if you are going to learn OJB right then spend some time scouring the > scads of source and see what is truly going on. "Use the source Luke!" :-) > Personally, I just don't have the time for that and I am more productive > using a tweak of the Sun recommended DAO Pattern. > > Brandon Goodin > Phase Web and Multimedia > P (406) 862-2245 > F (406) 862-0354 > [EMAIL PROTECTED] > http://www.phase.ws > > > -----Original Message----- > From: Joel Wickard [mailto:[EMAIL PROTECTED]] > Sent: Saturday, January 25, 2003 7:00 AM > To: Struts Users Mailing List > Subject: Re: Struts and OJB > > > James Mitchell wrote: > > >Yes, I agree (almost).....you can (so I've heard) change it so that > >those required internal tables are in another database, but for now I > >don't really mind. > > > > > > > Yeah, I just fixed the problem by using a different o/r mapping tool. > > > -- > To unsubscribe, e-mail: > <mailto:[EMAIL PROTECTED]> > For additional commands, e-mail: > <mailto:[EMAIL PROTECTED]> > > > > -- > To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> > For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> > -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]> -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
