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XML_DB support - level 0
OK, I've rewritten XMLResourceImpl and CollectionImpl to use a XMLContainer
instead of a Node.
When doing so I introduced some problems with getting a database reference
for the Ozone persistent objects (super.database() resulted in a "not
serializable" exception) that i cannot figure out right now but I suspect I
made some wrong assumptions and are treating client side code as if is was
inside the db.
I "fixed" it by moving stuff from XMLResourceImpl to CollectionImpl and what
i have now works and is level 0 compliant as far as i can tell. I was hoping
someone could review it and provide some feed-back so that we could clean it
up and commit it before I move on to level 1.
Does anyone have time?
Best regards,
Per
> -----Original Message-----
> From: ozone-dev-owner@ozone-db.org
> [mailto:ozone-dev-owner@ozone-db.org]On Behalf Of Lars Martin
> Sent: den 7 juni 2001 17:48
> To: ozone-dev@ozone-db.org
> Subject: Re: DB implementation - Relationships between Collection,
> Resource and XMLContainer
>
>
> On Thu, 7 Jun 2001 15:47:49 +0200
> "Per Nyfelt" <per.nyfelt@nordicwave.com> wrote:
>
> > I got a response on the XML:DB list confirming the idea that Resources
> > should be contained in Collections so I moved on using the (to
> me) simplest
> > interpretation of that idea which is to have a Map in
> CollectionImpl that
> > has id as their key and the Resource object as the value. For the
> > XMLResourceImpl i chose to use a Node as the content for the
> Resource. I'm
> > now able to test all use cases for DOM successfully and are moving on to
> > the String based stuff now.
> >
> > I'm not sure if choosing Node for Resource content is right. it
> works but
> > maybe I'm not considering all scenarios. When Lars put the
> skeleton code in
> > CVS he seemed to have had the idea to use an XMLContainer for
> the content
> > instead of Node.
>
> Are you using a persistent DOM Node or how do you ensure to make a
> node persistent in ozone? The reason why I used XMLContainer instead
> of Node as a member of XMLResource is that XMLContainer already
> implements helper methods to store/retrieve content (SAX, DOM, ...)
> in a very efficient way (streaming). Without this you have to re-
> implement such features because you'll come to the point where you'll
> need them.
>
> My aim was/is to preserve the current OzoneXML-API (except of the
> addition of collections). Therefore I would like to see the XML:DB API
> on top of ozoneXML, because the ozoneXML API is much "rawer" then
> XML:DB.
>
> On the other hand I don't want to mix the implementation of XML:DB
> with the core ozone features like proxies, database objects, ...
> If you will take a look at the "xml/core" module you'll find the
> counterpart of XMLContainer what is the persistent XMLCollection.
>
> > The difference would basically be:
> >
> > 1. Use aggregation. The Collection is stored in Ozone and it contains
> > XMLResources which contains Node objects. I changed the
> constructor to work
> > with this idea i.e.
> > public XMLResourceImpl( String id, OzoneInterface database,
> Collection
> > collection) {
> >
> > this.database = database;
> > this.collection = collection;
> > this.id = id;
> >
> > }
> >
> > 2. Use association. Both Collections and the XML as XMLContainers are
> > explicitly stored in Ozone. The Collection would not have a Map
> but instead
> > a list of id's that allows for the XML document to be found using
> > objectForName(id). For this to be smooth a getName() method
> should be added
> > to XMLContainer so that id does not have to be specified twice in the
> > construction of the XMLRersourceImpl. i.e.
> >
> > public XMLResourceImpl( OzoneInterface database, Collection
> collection,
> > XMLContainer container ) {
> > this.database = database;
> > this.container = container;
> > this.collection = collection;
> > this.id = container.getName();
> >
> > }
> >
> > Any ideas/suggestions?
> >
> > Best regards,
> > Per
> >
> > > -----Original Message-----
> > > From: ozone-dev-owner@ozone-db.org
> > > [mailto:ozone-dev-owner@ozone-db.org]On Behalf Of Per Nyfelt
> > > Sent: den 30 maj 2001 10:52
> > > To: ozone-dev@ozone-db.org
> > > Subject: XML:DB implementation - Relationships between Collection,
> > > Resource and XMLContainer
> > >
> > >
> > > I'm struggling with CollectionImpl.createResource(). What
> should be the
> > > relationships between org.xmldb.api.base.Collection,
> > > org.xmldb.api.base.Resource and org.ozoneDB.xml.util.XMLContainer? I
> > > something like the following in mind but I'm not sure this is a
> > > valid route:
> > >
> > > public Resource createResource( String id, String type ) throws
> > > XMLDBException {
> > > try {
> > > if ( ( id == null ) || ( id.equals("") ) ) {
> > > id = createId();
> > > }
> > > if ( type.equals(XMLResource.RESOURCE_TYPE) ) {
> > > // what to do with this?
> > > return new XMLResourceImpl(database,this,
> > > XMLContainer.newContainer( database, id));
> > > }
> > > else if ( type.equals(BinaryResource.RESOURCE_TYPE) ) {
> > > throw new XMLDBException( ErrorCodes.VENDOR_ERROR,
> > > "BinaryResource: Not yet implemented");
> > > }
> > > else {
> > > throw new
> > > XMLDBException(ErrorCodes.UNKNOWN_RESOURCE_TYPE);
> > > }
> > > }
> > > catch (Exception e) {
> > > throw new XMLDBException(ErrorCodes.UNKNOWN_ERROR,
> > > e.toString());
> > > }
> > > }
> > >
> > > Then for CollectionImpl.storeResource() i'm not sure how the
> storage of a
> > > Resource should be viewed. If Collection should aggregate Resources we
> > > should store the resource inside the Collection but then
> > > Collection needs to
> > > have a list (Map) of Resources. On the other hand if we store it as a
> > > separate object what denoted its relationship with a Collection?
> > >
> > > public void storeResource( Resource res ) throws XMLDBException {
> > > try {
> > > String id = res.getId();
> > > if ((id == null) || (id.length() == 0)) {
> > > id = createId();
> > > }
> > > // what to do whith this?
> > > database.createObject( Resource.class.getName(),
> > > OzoneInterface.Public, id);
> > > }
> > > catch (Exception e) {
> > > throw new XMLDBException(ErrorCodes.UNKNOWN_ERROR,
> > > e.toString());
> > > }
> > > }
> > >
> > > Any suggestions?
> > >
> > > Best regards,
> > > Per
> > >
> > >
> >
>
>
> --
> ______________________________________________________________________
> Lars Martin mailto:lars@smb-tec.com
> SMB GmbH http://www.smb-tec.com
>
>