RE: Incremental development

On Fri, 2006-01-13 at 13:23 +0000, Aidan Slingsby wrote:
> > On Fri, 2006-01-13 at 13:08 +0000, Aidan Slingsby wrote:
> > > When a new method is added to an ozone object, existing persistent 
> > > instances in the database no longer work.  If there a way of easily 
> > > updating all the instances in the database to the new class 
> > > definition, or can this only be done by keeping the old class 
> > > definition too and create new instances of the new class, copying the 
> > > data over and deleting the old ones (or using XML or ASCII 
> > > export/import)?  With relational databases, it is relatively easy to 
> > > change table design without corrupting the data - can this be the case 
> > > in Ozone too (if I do something differently).
> > 
> > What exactly do you mean by 'no longer work'?
> 
> What I mean is that if write a CarImpl class, store some data in an Ozone
> database, then edit the code and add fields and methods to get and set a
> colour for the car, run OPP again and try and retrieve a car (stored before
> the class was modified) it will say that the class isn't found (if I'm not
> mistaken).  I can understand why adding a new field would cause problems
> (the binary storage is different).  Anyway, in a relational database, one
> could just add a new 'colour' column.  I wondered if something like this
> could easily be done in Ozone.

If the class is not found you have a classpath problem. But I am afraid
that unless you know what the exact error is, noone can help you
elaborate on the cause...



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