EntityBeans and OJB

["Anton S. Komratov" <a....@lynx.ru>]

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?



best regards,
Anton Komratov

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Re: EntityBeans and OJB

[Andreas Bohnert <ab...@online.de>]

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" <th...@web.de>
To: "OJB Users List" <oj...@db.apache.org>
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: ojb-user-unsubscribe@db.apache.org
> > For additional commands, e-mail: ojb-user-help@db.apache.org
> >
> >
>
>
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>


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Re: EntityBeans and OJB

[Thomas Mahler <th...@web.de>]

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: ojb-user-unsubscribe@db.apache.org
> For additional commands, e-mail: ojb-user-help@db.apache.org
> 
> 


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