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From Rainer Döbele <doeb...@esteam.de>
Subject re: [jira] Updated: (EMPIREDB-97) Serialization of Empire-DB objects
Date Wed, 26 Jan 2011 22:36:39 GMT
Hi Eike,

I can follow your conclusion and agree that making ErrorObject serializeable makes no sense
(why would anyone want to serialize an error anyway?), whereas serializing EmpireException
is fine.

I have not applied your patch yet (but I will do), but there is one more thing that came to
my mind:
DBReader is not serializeable as it requires a reference to an open java.sql.ResultSet.
We have to make sure, that that a NotSerializeable exception is thrown, when attempting to
serialize this class. 

Thanks and regards,
Rainer


Eike Kettner (JIRA) wrote:
> from: Eike Kettner (JIRA) [mailto:empire-db-dev@incubator.apache.org]
> to: empire-db-commits@incubator.apache.org
> re: [jira] Updated: (EMPIREDB-97) Serialization of Empire-DB
> objects
> 
> 
>      [ https://issues.apache.org/jira/browse/EMPIREDB-
> 97?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
> 
> Eike Kettner updated EMPIREDB-97:
> ---------------------------------
> 
>     Attachment: 1_dbobject.patch
>                 0_exception.patch
> 
> Hi there,
> 
> As I started working on the serialization thing, I figured that it's
> not a good idea to let ErrorObject implement Serializable. Nearly every
> object extends ErrorObject and for some (and especially for objects to
> come) it is not desireable to be serializable. I think its not that
> good
> to open so many object for serialization. Then there are already
> classes
> that hold non-serializable references (I found XMLConfiguration to be
> such a class). So, I think it could be a source of bugs to open every
> object this way...
> 
> The other side is, that ErrorObject uses a static ThreadLocal to hold
> error info. This wouldn't be serialized anyways. This means
> EmpireException wouldn't be serializable even if ErrorObject implements
> Serializable.
> 
> Instead I chose to serialize EmpireException by using a serializable
> implementation of ErrorInfo. The major difference here: EmpireException
> does not hold a reference to the concrete object anymore, but only a
> copy of the error infos. IMHO, this is good for an exception, but I
> have
> no glue to what extend users rely on EmpireException#getErrorObject to
> return a DBTable, XMLConfiguration etc. This is applied with the first
> patch.
> 
> Then I chose to let DBObject implement Serializable. I think that it's
> nice if data model objects are serializable. Plain SQL strings are
> serializable and so I think objects like DBCommand or DBOrderByExpr
> (that represent parts of SQL) should be serializable, too :). This is
> applied in the second patch.
> 
> Regards,
> Eike
> 
> 
> > Serialization of Empire-DB objects
> > ----------------------------------
> >
> >                 Key: EMPIREDB-97
> >                 URL: https://issues.apache.org/jira/browse/EMPIREDB-
> 97
> >             Project: Empire-DB
> >          Issue Type: Wish
> >          Components: Core
> >            Reporter: Eike Kettner
> >         Attachments: 0_exception.patch, 1_dbobject.patch
> >
> >
> > Looking at class EmpireException, it holds references to two non-
> serializable objects: ErrorObject and ErrorType which breaks the
> contract with the Exception API.
> > Now, it would be great for several use-cases to have Empire-DB
> objects serializable. If ErrorObject would be serializable, it would
> first make EmpireException serializable (assuming ErrorType to be
> serializable) and next it would make every other DBXyz object in this
> hierarchy serializable.
> > Here is for reference the mail thread from users@ mailing list:
> > ------------------------------
> > On Sat, Jan 22, 2011 at 7:26 PM, Eike Kettner <news@eknet.org> wrote:
> > > Hi Rainer and Francis,
> > >
> > > thanks for your quick replies and for giving this a chance.
> Serializing
> > > an exception is sure not something massive used, however sometimes
> it is
> > > quite a nice feature. For example, a JMSLogger sends log events to
> a
> > > broker, and there exceptions are serialized. Well, I see that this
> is
> > > not used often, and more or less a "special case" :). Still, I
> would
> > > consider a non-serializable exception a small "bug" - just because
> it's
> > > dictated by the java api.
> > >
> > > I had a quick look at the sources and as far as I can see, it
> should be
> > > ok to make "everything" serializable. There is always the
> > > "serializable-drawback" to consider: users can save objects on disk
> and
> > > later try to load them with a new version of empire-db, where class
> > > definitions have changed. Well, I think one can live with this, and
> it
> > > does not apply to many other use-cases of serialization (rmi,
> > > serialization used in wicket or messaging), because objects are
> > > serialized only for a short amount of time.
> > >
> > > Regards,
> > > Eike
> > >
> > > On [Sat, 22.01.2011 13:49], Rainer D=F6bele wrote:
> > >> Hi Eike,
> > >>
> > >> I agree with Francis that I don't quite see the point for
> serializing an Exception, although I must admit that
> java.lang.Throwable is Serializable.
> > >>
> > >> But then I agree that we should consider making DBObject or
> ErrorObject serializeable which then would apply to the entire object
> hierarchy.
> > >> Regards
> > >>
> > >> Rainer
> > >>
> > >>
> > >> Francis De Brabandere wrote:
> > >> > from: Francis De Brabandere [mailto:francisdb@gmail.com]
> > >> > to: empire-db-user@incubator.apache.org
> > >> > re: Re: Serialization of EmpireException
> > >> >
> > >> > Hi Eike,
> > >> >
> > >> > I see no reason for not making them Serializable.
> > >> >
> > >> > Rainer?
> > >> >
> > >> > Cheers,
> > >> > Francis
> > >> >
> > >> > On Fri, Jan 21, 2011 at 4:31 PM, Eike Kettner <news@eknet.org>
> wrote:
> > >> > >
> > >> > > Hello,
> > >> > >
> > >> > > I was trying to serialize EmpireException but ran into an
> error.
> > >> > > EmpireException is marked as Serializable (RuntimeException)
> > >> > > but it holds references to ErrorObject and ErrorType which are
> not
> > >> > > serializable. Hence a NotSerializableException is thrown.
> > >> > >
> > >> > > When asking this, I like to ask whether there is a thought
> about making
> > >> > > some model objects like DBRowset DBTable etc serializable.
> Since most or all
> > >> > > DBXyz objects hold model information only it should be okay
> for them to
> > >> > > be serializable, imho? I use messaging and often Apache Wicket
> which
> > >> > > both use serialization, that's why I'm asking this. (For
> example, I'd
> > >> > > like to pass around where and order-by expressions).
> > >> > >
> > >> > > Kind Regards,
> > >> > > Eike
> > >> > >
> > >> > >
> > >> > >
> > >> >
> > >> >
> > >> >
> > >> > --
> > >> > http://www.somatik.be
> > >> > Microsoft gives you windows, Linux gives you the whole house.
> > >>
> > >
> 
> --
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