Re: [udig-devel] Proposal - Export To ....

[Chris Holmes <cholmes@xxxxxxxxxxxxx>]

On 9/23/05, Jody Garnett <jgarnett@xxxxxxxxxxxxxxx> wrote:
> Diatchkov Vitali wrote:
> 
> > We have good framework for importing data into UDIG. Wizards, wizard
> > pages and etc. are configured as extentions and the workflow is
> > uniform that is good. Are there plans to create the same framework of
> > UI components for exporting anything from UDIG to anything outside? Or
> > is common Eclipse platform functionality enough for those purposes?
> >
> > I want, for example, to merge any number of layers with features of
> > the same type to one layer and export it as a shapefile.. The issue: I
> > again want to follow to common concept of exporting from UDIG.. as it
> > exists with importing approach. Any suggestions.
> >
> The answer is somewhere in between, the Eclipse infrastructure is good
> enough. But we like to make things easy, please see the DataAccess Guide
> for an outline of a plan for moving export operations in that direction.
> -<http://udig.refractions.net/docs/uDig-DataAccessGuide.pdf>
> 
> There are some RnD links in the geotools wiki on this topic as well.
> 
> They all amount to the same thing, at the end of the day, given a
> FeatureType and a features to write out a framework can be constructed
> allowing the user to  "Export to..." a shapefile, a database table, 
etc....
> 
> As an example trial consider:
> 
-<http://udig.refractions.net/confluence/display/COM/ExportSelectedFeatures>
> 
> The "operation" is simple, the selected features. The process of
> exporting is hard coded to shapefile, but that can be changed. The
> important point is that both the FeatureType to create, and the ability
> access the data to be written is available.

I think we actually need an improvement in GeoTools on this front, for
'export'.  I think we should have a SPI plug-in mechanism for writers,
just like we do for readers (datastore).  Yes, datastores do write, that's
one of their big purposes, but they sort of more 'edit' than write.  
Basically I'm thinking of like an output writer for PostGIS that like
ogr2ogr or shp2pgsql writes out the sql statements to disk.  In the
current scheme the 'write all' operation is second tier to update, delete,
insert.  In shapefile it happens to write everything out in the backend,
but it's not really a full part of the api.  granted there should be lots
of code re-use between the update/delete/insert and the output writer,
PostGIS should find a way to use the same live statements to write them
out to files.. But I think the output writer should perhaps have it's own
interface.  GeoServer could also make use of these directly, as 'output
formats' for WFS.  I think Brent just wrote one for Shapefile, and we have
one for GML (the default), and zipped GML.  These should be ale to share
lots of code with the udig output, but I believe we should consider a
slightly higher level API.  this would make a geotools2geotools little 
swing program to convert from one format to another a cinch.

Chris