[fdo-internals] providers.xml vs. FdoIConnectionInfo

[Robert Fortin]

Historically,  the provider were registered to the Fdo registery manager
by passing the information retrieved by the connection object itself.
That way there was no disconnection between the data from the connection
and the data in the providers.xml.

If the edit is done manually, there is no guarantee that the 2
informations will be consistant.  At the moment, the important part is
the mapping between the name and the library to load so CreateConnection
can work correctly. 

RF

-----Original Message-----
From: fdo-internals-bounces at lists.osgeo.org
[mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Mateusz
Loskot
Sent: Thursday, February 22, 2007 3:14 PM
To: FDO Internals Mail List
Subject: Re: [fdo-internals] providers.xml vs. FdoIConnectionInfo

Traian Stanev wrote:
> Hi,
> 
> FdoIConnectionInfo exposes the following functions:
> 
>     FdoString* GetProviderName()
>     FdoString* GetProviderDisplayName()
>     FdoString* GetProviderDescription()
>     FdoString* GetProviderVersion()
>     FdoString* GetFeatureDataObjectsVersion()
>     
> 
> The same information is also available in the providers.xml file entry

> for the provider.

According to my understanding, the most important part of the
providers.xml registry is name + location of provider + its library.
Rest of information is only here for convenience, so it's not required
to scan and query every provider for these details, for instance when
application is about to list them in user-friendly way.

I had similar question when started to test my fdopostgis with the
Hammerhead. I revealed that when I put fdopostgis entry to the
providers.xml but the DLL is not available under specified path, the
Hammerhead doesn't complain but lists the fdopostgis in the Data Connect
dialog box.

Later, I was told that this behavior is intentional and providers should
not be loaded & queried on application launch. So, without these details
in the providers.xml, it would not be possible.

> Which copy of the information are applications supposed to use?

I think it depends if you want to load the provider or not.

> What if the two are out of sync?

I don't suppose this is a problem, except misinforming a user :-)

Cheers
--
Mateusz Loskot
http://mateusz.loskot.net
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