I will go through your mails and come back to that.
Andrea
On Dec 13, 2007, at 7:40 PM, Jody Garnett wrote:
Morning Moovida; this email is a replacement for your Thursday IRC
meeting ;-)
It seems that there has been a break down of trust between the
project and the catalog layers of our application. I was not aware of
this change when it was introduced, it seems that the project plugin
is using both:
- "layer id" to look up an entry in the catalog; and
- it was also using the connection parameters
There is a relationship between layer id, and connection parameters.
They need to be exactly in sync or the catalog starts getting confused.
I was surprised that this was even possible - here is how it was done:
- IServiceFactory.acquire( id, params )
The javadocs for this method say: "is intended to be used when
replacing an IService entry in a catalog". This method is used by the
catalog framework when setting up for a replacing a moved service, ie
it is a step that is needed when we are about to fire a REPLACE event.
So what has happened is when lazy loading of a map was introduced;
maps were no longer around to listen to REPLACE events and thus could
not be kept in sync with the catalog. The above acquire method was
used to allow these out of sync map layers to fumble along using an
ID that did not exactly match the intrinsic identity of the resource
on disk.
This amounts to a breakdown of trust between the two systems :-) The
concept of an ID is no longer trusted by layer to a be a good handle
for resource lookup; this is something we can fix.
I would like to introduce a "IForward" class into the catalog;
something that can be left behind in the catalog when a resource is
moved. That way projects that were closed still have a way of
noticing and fixing themselves when they are loaded. These handles
can be used just alike a IService returned from a search; they can
act as a wrapper for the actual service (so simple code can stay
simple), although I will make them printin warning messages if uDig
is being run in -debug mode.
It is my hope that with this addition trust can be established again
and the project layer implementation can be simplified, and made much
less insane ;-)
Jody
