Re: [INTERFACES] query java object?

Hi all,

OK, hopefully this all makes sense...

<background>
The enterprise java beans spec specifies that classes
requiring (CMP) persistence need to let the container know
which attributes to persist by way of an XML
descriptor.
</background>

So, given that we only want to persist certain properties/attributes
of a particular Java class is this possible using the mechanism
described below?

Also, what are the overheads involved here? I guess the table
will need to be created the first time an object of a particular
type is stored, after that it should fairly normal?

I'd love to be able to come up with a container-managed-persistence
module based on PostgreSQL for EJBOSS (www.ejboss.org), but
I'm still sorting things out in my head as to the best ways of doing this.

One little weird one, given that the Java classes you persist actually
persist other classes they reference (as long as they're defined in
PostgreSQL mapping I guess), would a way around the cyclic
reference problem be to check the .equals() method when storing
chained objects, maintain a hashtable for each root node and not
store the object if it has already been done? That seems awfully
simplistic, what are the issues involved?

Regards,
Joe.

----- Original Message -----
From: "Peter Mount" <petermount(at)it(dot)maidstone(dot)gov(dot)uk>
To: "'Phillip Rhodes'" <rhodespc(at)bellatlantic(dot)net>;
"'pgsql-interfaces(at)postgresql(dot)org'" <pgsql-interfaces(at)postgreSQL(dot)org>
Sent: Thursday, January 06, 2000 1:50 AM
Subject: RE: [INTERFACES] query java object?

> Yes of sorts. We have a small extension that allows a Serialized object
> to be stored in one or more tables (rather than as a stream). Once
> serialized in this way, you can then query the stored objects just like
> any other SQL Table.
>
> Peter
>
> --
> Peter Mount
> Enterprise Support
> Maidstone Borough Council
> Any views stated are my own, and not those of Maidstone Borough Council.
>
>
>
> -----Original Message-----
> From: Phillip Rhodes [mailto:rhodespc(at)bellatlantic(dot)net]
> Sent: Monday, January 03, 2000 2:11 AM
> To: 'pgsql-interfaces(at)postgresql(dot)org'
> Subject: [INTERFACES] query java object?
>
>
> I read through the documentation for Postgres and Java, but I am a
> little
> unclear on something: (probably a few things!)
>
> Is it possible to execute a query based on the attributes of a
> serialized
> object? Or do I have to instantiate each object and do an if test?
>
>
> Thanks!
>
> Phillip
>
>
>
> ************
>
> ************
>