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Posted to users@tapestry.apache.org by tsvetelin <ts...@rushmore-digital.com> on 2003/11/05 16:55:18 UTC
RE: [Fwd: Re: OJB, Tapestry, Serialized Objects and a questforanswers.]
Hi John,
You don't need to encode the class name in your JDO squeezer because this is
handled by JDO implementations.
Here are 2 cases that are possible.
The first one is when the JDO implementation define your JDO identity class.
In this case the JDO implementation use its identity class. This class
contains the primary keys for your object (in the most cases it is a int or
long value) and the class name of corresponded data object. When you take
the string presentation of the identity instance it encode class name. So
the JDO implementation know persistence class name for each instance of
identity object. For example I am using the Kodo JDO and their identity
class is: com.solarmetric.kodo.util.ObjectIds$Id. It contains 2 properties.
long and persistence class
The second case is when you define the identity class for particular
persistent class in package.jdo file. For more information please see the
JDO metadata(<!ATTLIST class identity-type (application|datastore|none)
'datastore'> and <!ATTLIST class objectid-class CDATA #IMPLIED> ). In this
case the JDO implementation know which is associated persistent class for
particular identity object.
I hope that this will be useful.
Tsvetelin
-----Original Message-----
From: John Meredith [mailto:psynix@t-online.de]
Sent: Wednesday, November 05, 2003 4:48 PM
To: Tapestry users
Subject: Re: [Fwd: Re: OJB, Tapestry, Serialized Objects and a
questforanswers.]
Possibly a stupid question (and somewhat OT), do you have an Adaptor for
each JDO and if not, how do you get from the oid back to the object
without distinguishing between your ModelObjects? Or does JDO encode
this into the oid?
I generally use integer sequences for my iod (provided by the DB), which
is why I've had to encode the classname as well.
Just interested in how other people are doing this :-)
- John
On Wed, 2003-11-05 at 12:23, Ryan Moffat wrote:
> Yeah that's pretty much how the JDO squeezer is written. My only change
is
> that my persitance capable classes all implement a common interface
(always
> found this usefull) defining a getId() method which I use in the Squeezer.
>
> /**
> * Squeezes the {@link is.symbian.framework.model.ModelObject} data
to
> it's oid string
> */
> public String squeeze(DataSqueezer squeezer, Object data) {
> is.symbian.framework.model.ModelObject jdoObject =
> (is.symbian.framework.model.ModelObject) data;
> return PREFIX + jdoObject.getObjectId().toString();
> }
>
> /**
> * Un-squeezes a jdo object using it's oid string to locate it.
> */
> public Object unsqueeze(DataSqueezer squeezer, String string) {
> PersistenceManager pm = JDOSupport.getPM();
> if (string.length() == PREFIX.length()) return ""; // Probably a
> problem
> Object o = pm.newObjectIdInstance(null,
> string.substring(PREFIX.length()));
> return pm.getObjectById(o, true);
> }
>
> Cheers
> Ryan Moffat
>
> ----- Original Message -----
> From: "John Meredith" <ps...@t-online.de>
> To: "Tapestry users" <ta...@jakarta.apache.org>
> Sent: Wednesday, November 05, 2003 10:29 AM
> Subject: Re: [Fwd: Re: OJB, Tapestry, Serialized Objects and a quest
> foranswers.]
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: tapestry-user-unsubscribe@jakarta.apache.org
> For additional commands, e-mail: tapestry-user-help@jakarta.apache.org
--
John Meredith <ps...@t-online.de>
---------------------------------------------------------------------
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RE: [Fwd: Re: OJB, Tapestry, Serialized Objects and a
questforanswers.]
Posted by John Meredith <ps...@t-online.de>.
Thanks for the explanation Tsvetelin, cleared things up :-)
Rgds,
- John
On Wed, 2003-11-05 at 16:55, tsvetelin wrote:
> Hi John,
>
> You don't need to encode the class name in your JDO squeezer because this is
> handled by JDO implementations.
> Here are 2 cases that are possible.
>
> The first one is when the JDO implementation define your JDO identity class.
> In this case the JDO implementation use its identity class. This class
> contains the primary keys for your object (in the most cases it is a int or
> long value) and the class name of corresponded data object. When you take
> the string presentation of the identity instance it encode class name. So
> the JDO implementation know persistence class name for each instance of
> identity object. For example I am using the Kodo JDO and their identity
> class is: com.solarmetric.kodo.util.ObjectIds$Id. It contains 2 properties.
> long and persistence class
>
> The second case is when you define the identity class for particular
> persistent class in package.jdo file. For more information please see the
> JDO metadata(<!ATTLIST class identity-type (application|datastore|none)
> 'datastore'> and <!ATTLIST class objectid-class CDATA #IMPLIED> ). In this
> case the JDO implementation know which is associated persistent class for
> particular identity object.
>
>
> I hope that this will be useful.
>
> Tsvetelin
>
> -----Original Message-----
> From: John Meredith [mailto:psynix@t-online.de]
> Sent: Wednesday, November 05, 2003 4:48 PM
> To: Tapestry users
> Subject: Re: [Fwd: Re: OJB, Tapestry, Serialized Objects and a
> questforanswers.]
>
>
> Possibly a stupid question (and somewhat OT), do you have an Adaptor for
> each JDO and if not, how do you get from the oid back to the object
> without distinguishing between your ModelObjects? Or does JDO encode
> this into the oid?
>
> I generally use integer sequences for my iod (provided by the DB), which
> is why I've had to encode the classname as well.
>
> Just interested in how other people are doing this :-)
>
> - John
>
> On Wed, 2003-11-05 at 12:23, Ryan Moffat wrote:
> > Yeah that's pretty much how the JDO squeezer is written. My only change
> is
> > that my persitance capable classes all implement a common interface
> (always
> > found this usefull) defining a getId() method which I use in the Squeezer.
> >
> > /**
> > * Squeezes the {@link is.symbian.framework.model.ModelObject} data
> to
> > it's oid string
> > */
> > public String squeeze(DataSqueezer squeezer, Object data) {
> > is.symbian.framework.model.ModelObject jdoObject =
> > (is.symbian.framework.model.ModelObject) data;
> > return PREFIX + jdoObject.getObjectId().toString();
> > }
> >
> > /**
> > * Un-squeezes a jdo object using it's oid string to locate it.
> > */
> > public Object unsqueeze(DataSqueezer squeezer, String string) {
> > PersistenceManager pm = JDOSupport.getPM();
> > if (string.length() == PREFIX.length()) return ""; // Probably a
> > problem
> > Object o = pm.newObjectIdInstance(null,
> > string.substring(PREFIX.length()));
> > return pm.getObjectById(o, true);
> > }
> >
> > Cheers
> > Ryan Moffat
> >
> > ----- Original Message -----
> > From: "John Meredith" <ps...@t-online.de>
> > To: "Tapestry users" <ta...@jakarta.apache.org>
> > Sent: Wednesday, November 05, 2003 10:29 AM
> > Subject: Re: [Fwd: Re: OJB, Tapestry, Serialized Objects and a quest
> > foranswers.]
> >
> >
> > ---------------------------------------------------------------------
> > To unsubscribe, e-mail: tapestry-user-unsubscribe@jakarta.apache.org
> > For additional commands, e-mail: tapestry-user-help@jakarta.apache.org
> --
> John Meredith <ps...@t-online.de>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: tapestry-user-unsubscribe@jakarta.apache.org
> For additional commands, e-mail: tapestry-user-help@jakarta.apache.org
--
John Meredith <ps...@t-online.de>