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Re: Limitation of Ozone -- Cant return an iterator
On Sat, 02 Dec 2000, Neil Aggarwal wrote:
> Falko:
>
> Thanks for the help. But, this leads me to another question:
>
> What is the best way to return a collection of objects
> from the database?
>
> For example, if I want to retrieve all objects with a given
> attribute value.
>
> Is it best to declare my own collection class that has
> a proxy and then fill that collection and return the proxy
> object for the collection.
>
> It seems like then Ozone should have a library of collection
> classes for operations like this.
>
> They could really be wrappers around the Java collection
> classes.
Returning a java2 collection that holds database objects (actually their
proxies) is, in contrast to your approach to return the iterator for it, no
problem.
For example: if your database object holds all employees, which inturn are
database objects, in a java2 collection, then it may select some of them, put
them in a new collection and return it to the caller. Whether this caller is the
client or another database objects doesn't make a difference.
Falko
>
> Thanks,
> Neil.
>
>
> > In your code you are trying to manipulate the internal data of an database
> > object via ordinary Java references. The hashmap iterator keeps a ordinary
> > java reference to the hashmap to do its job. It knows nothing about ozone's
> > persistent references (proxies). After the iterator is serialized thru the
> > socket connection its references are no longer valid in the new VM.
> >
> > Besides, java.util.HashMap$HashIterator is plain and simple not serializable.
> > One could hardly tell this a limitation of ozone.
>
> --
> Neil Aggarwal
> JAMM Consulting, Inc. -- (972) 612-6056, http://www.JAMMConsulting.com
> Custom Internet Development -- Java, JSP, servlets, databases
--
______________________________________________________________________
Falko Braeutigam mailto:falko@smb-tec.com
SMB GmbH http://www.smb-tec.com