This brings up related points that RDBMS folks have been making for some
time concerning flaws in EJB. Persistence not being an official SPI but
rather bundled into pieces of EJB, JDBC and Connector specs, most of the
difficult problems aren't directly addressed in a J2EE spec. Dave Wolf of
Sybase has referred to the persistence issue as the great white elephant
sitting in the J2EE room that no one wants to mention by name, though we're
all propping our feet up on it. I guess Dave has a good sense of humor.
Dave and others make a case that EJB is useful only when it does have
exclusive access to the underlying datastore (making commit option A the
only viable solution). Even simple issues like discrepancies between
ejbStore and ejbLoad (if external apps can access the database, the data may
change between a load and store, causing the bean to be out of sync with the
actual data even though the EJB server has carefully locked access within
its realm to properly sync all EJB's) are addressable only through
DB-specific methods or true XA drivers (not XA wrappers provided by pooling
code, but drivers) and some DB vendor-specific syntax. More complex issues
than this exist, and diamond scenarios proliferate.
There are quite strong workarounds for much of these issues -- using
messaging between views, complex deployment schemes, relying on
Oracle-specific or Sybase-specific products and syntax, etc. -- but it would
be helpful, in my humble opinion, to see some concerted direction from Sun
in the form of an SPI that takes a stab at addressing the persistence issues
in a way that consolidates CMP, Connector, JDBC, and even that current Sun
political pariah, JDO.
For now, patterns and pattern languages such as those mentioned on The
Server Side suffice as a starting point -- not a silver bullet, but a viable
starting point -- for handling such issues in specific vertical apps.
Sean
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of
Schaefer, Andreas
Sent: Tuesday, April 10, 2001 2:33 PM
To: '[EMAIL PROTECTED]'
Subject: RE: [JBoss-dev] Object Unique Id Generator
There is a conceptual issue I like to raise here. From my
point of view the "Unique Key" is part of the DB and therefore
under the ownership of the DB. The idea I saw there would
work under some assumptions:
- DB belongs only to the application
- There is no interaction with the DB except through the EJBs
- DB is only the persistence tool
If you want to add data to the DB through the DB directly
like an import or through a backup.
The Unique Key is a DB concept and therefore I think the
key generation should remain within the DB.
Have fun - Andy
> -----Original Message-----
> From: Sean Neville [mailto:[EMAIL PROTECTED]]
> Sent: Tuesday, April 10, 2001 11:01 AM
> To: '[EMAIL PROTECTED]'
> Subject: RE: [JBoss-dev] Object Unique Id Generator
>
>
> There are a series of key generation patterns available on
> The Server Side,
> at least one of which requires no databases and no singletons, and is
> therefore quite portable:
>
> http://www2.theserverside.com/patterns/index.jsp
>
>
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of
> Schaefer, Andreas
> Sent: Tuesday, April 10, 2001 1:22 PM
> To: '[EMAIL PROTECTED]'
> Subject: RE: [JBoss-dev] Object Unique Id Generator
>
>
> Hi Geeks
>
> The "FOR UPDATE" is not always necessary as like in Oracle you
> have a sequence generator delivering you an unique ID.
>
> For the other DBs it is maybe better to use a DB procedure or
> function to generate an unique ID than use a SQL Statement.
>
> Have fun - Andy
>
> > -----Original Message-----
> > From: Emmanuel Sciara [mailto:[EMAIL PROTECTED]]
> > Sent: Tuesday, April 10, 2001 9:28 AM
> > To: [EMAIL PROTECTED]
> > Subject: [JBoss-dev] Object Unique Id Generator
> >
> >
> > Hi guys,
> >
> > I have written an advanced key generator for ejbs
> > (http://ejbutils.sourceforge.net/). I would like to possibly have it
> > blundled with JBoss. For this however, I need a database that
> > supports "FOR
> > UPDATE" sql clauses or transactions with serializable
> isolation level.
> >
> > >From what I know, Hypersonic does not provide that and I
> > moved away from
> > InstantDB early in the process because I had problems with
> > it, so I don't
> > know.
> >
> > So I guess, my question is two fold:
> > - Does JBoss have such database?
> > - If yes, do you think it would be worth blundling this stuff
> > with JBoss.
> >
> > Note: the source is a bit out of date on sourceforge but I am
> > working on it.
> > I have a fully JBoss-deployable version if you are interested.
> >
> > Emmanuel
> >
> > > From: "marc fleury" <[EMAIL PROTECTED]>
> > > > post this to jboss-dev, I remember there is a key
> > generator somewhere
> > but
> > > > yours might be more advanced. if you generate some
> > interest there, you
> > > are
> > > > on
> > > >
> > > > marc
> > > >
> > > >
> > > > |-----Original Message-----
> > > > |From: Emmanuel Sciara [mailto:[EMAIL PROTECTED]]
> > > > |Sent: Friday, April 06, 2001 10:31 AM
> > > > |To: marc fleury
> > > > |Subject: Re: Thanks
> > > > |
> > > > |
> > > > |Hey!
> > > > |
> > > > |Cool Idea! I am interested for sure. Just tell me where
> > to find the
> > right
> > > > |sample code and I am of! (if you can do that easily
> > enough, that would
> > > save
> > > > |me some time)
> > > > |
> > > > |Just need to modify my sql so it does not use "For
> > Update", which is
> > not
> > > > |supported by Hypersonic. I would like to write some doc
> > too. But I
> > guess
> > > > |that can wait if I send some explanation mail to the list.
> > > > |
> > > > |Any other suggestion you would have?
> > > > |
> > > > |Emmanuel
> > > > |
> > > > |----- Original Message -----
> > > > |From: "marc fleury" <[EMAIL PROTECTED]>
> > > > |To: "Emmanuel Sciara" <[EMAIL PROTECTED]>
> > > > |Sent: Thursday, April 05, 2001 6:28 PM
> > > > |Subject: Thanks
> > > > |
> > > > |
> > > > |> for removing the documentation from the website,
> > > > |>
> > > > |> also did you think about implementing the high/low
> pattern and
> > > > |putting it
> > > > |> as an MBean (or Bean) in JBoss?
> > > > |>
> > > > |> let me know if interested let the list know and see if
> > they want it.
> > > > |>
> > > > |> marc
> > > > |>
> > > > |>
> > > > |> _________________
> > > > |> Marc Fleury, Ph.D
> > > > |> [EMAIL PROTECTED]
> > > > |> _________________
> > > > |
> > >
> > >
> >
> >
> >
> > _______________________________________________
> > Jboss-development mailing list
> > [EMAIL PROTECTED]
> > http://lists.sourceforge.net/lists/listinfo/jboss-development
> >
>
> _______________________________________________
> Jboss-development mailing list
> [EMAIL PROTECTED]
> http://lists.sourceforge.net/lists/listinfo/jboss-development
>
> _______________________________________________
> Jboss-development mailing list
> [EMAIL PROTECTED]
> http://lists.sourceforge.net/lists/listinfo/jboss-development
>
_______________________________________________
Jboss-development mailing list
[EMAIL PROTECTED]
http://lists.sourceforge.net/lists/listinfo/jboss-development
_______________________________________________
Jboss-development mailing list
[EMAIL PROTECTED]
http://lists.sourceforge.net/lists/listinfo/jboss-development
