Hi Thomas, I'm also a newbie to application servers, so a couple of questions are comming up now.
Do you suggest to leave EJB's aside complety? I thought I'm supposed to use OJB within EJB's (like the OJB-EJB examples...) Are there also disadvantages if I work just with OJB and leave EJB aside? best regards andreas ----- Original Message ----- From: "Thomas Mahler" <[EMAIL PROTECTED]> To: "OJB Users List" <[EMAIL PROTECTED]> Sent: Thursday, September 04, 2003 11:57 AM Subject: Re: EntityBeans and OJB > Hi Anton, > > Anton S. Komratov wrote: > > The goal of both is to implement persistent. CMP is a part > > of EJB server, and OJB is third party product. > > > > Can anybody explain to newbie what are the advanteges of > > using OJB when there is a possibility to implement storing > > EntityBeans? > > EntityBeans have several disadvantages: > - No proper support for inheritance hierachies of entities > - No proper support for dealing transparently with 1:1, 1:n, n:m > associations > - Finder methods require sql coding or usage of the awkward EJBQL query > language > - EJB CMP does not give you control about the granularity of entity > object graphs. > - You also don't have control when to use lazy or eager loading. > - the last two point may lead to serious performance impacts for certain > application scenarios. > > Some of the above points are adressed with EJB 2.0 and certain CMP > implementations. But they are still typical problems. > A lot of EJB patterns is about how to work around inherent problems of > the CMP/BMP approach. > > A lot of software designers thus decided to not use CMP/BMP in their > J2EE applications, but to use classic O/R mapping tools (like TopLink or > OJB). > > A lot of EJB container vendors are working on JDO implementations. So I > personally expect that the JDO specification will be part of the EJB > spec at some point in time, and no one will have to use CMP/BMP, but can > use a JDO compliant O/R tool. > > [Apache Geronimo (the upcoming Apache J2EE Container) will have a > OJB-JDO implementation right from the start!] > > -Thomas > > > > > > > > > best regards, > > Anton Komratov > > > > --------------------------------------------------------------------- > > 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] > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
