[Gvsig_english] [ gvSIG 2.0 extension development ] How toimplement and register a new DAL provider

[luca bianconi]

Hi all,

thanks for the big explanation.
*
This document explains how you can create a new DataStore using the API. In
this example it is creating a new DBF. The "DBF provider" has to be
previously registered with a name or the line
"serverExplorer.**getAddParameters("DBF")"
will send an exception. *

How could I avoid it ? Could you show me how to do ?

Best regards,

Luca


2010/8/4 Jorge Piera Llodrá <jpiera at prodevelop.es>

>  On 08/04/2010 01:31 AM, luca bianconi wrote:
>
> Hi all,
>
> it has past some time since I've started studying gvSIG DAL providing
> system and, even if I've received many useful explanations (thanks kind
> Cèsar!), read longly the documentation [1] about it, read other DAL
> providers code, made coding tests, I'm unfortunately still plenty of doubts.
>
> I'd like asking the community some help to understand some things (I'm very
> sorry if some of them could sound very trivial to some of you).
>
> First of all, just a curiosity I'd like to ask Spanish speaking people :
> I understand the word "almacèn" as "provider", referred in documentation as
> the DAL provider. Is it correct ?
>
>
> I'm not completely agree. An "Almacén" is a "DataStore" that uses a
> provider (DataStoreProvider) to retrieve data from a data source.
>
> The "Almacen o DataStore" is the API of DAL that can be used by a data
> consumer to retrieve data. Providers are a part of the Service Provider
> Interface (SPI) and they register in DAL new formats that can be managed
> using the DAL API.
>
>
>
> If this is correct, and I want to register a new DAL provider I guess,
> after having of course read the whole available (as much as I know)
> documentation [1] on fmap.dal, I should use as main reference the chapter "Creación
> de un nuevo almacén" [2] .
>
>
> This document explains how you can create a new DataStore using the API. In
> this example it is creating a new DBF. The "DBF provider" has to be
> previously registered with a name or the line
> "serverExplorer.getAddParameters("DBF")" will send an exception.
>
>
> I've been suggested to give a glance, as example, at the extDwg extension
> for better understanding how the registration of a DAL provider works.
> I see that in this provider, as in other ones, four classes are always
> implemented:
>
> DWGLibrary -> Does it register the provider ? Does it in doPostInitialize()
> method ?
>
>
> Thats right. It registers the DWG provider and the DWG explorer that is
> used to browse by a directory tree for searching DWG's of creating new DWG's
>
>
> DWGFilesystemServerProvider, DWGStoreParameters, DWGStoreProvider -> How do
> they work exactly ? What do they do ?
>
>
> DWGFilesystemServerProvider -> It is used to browse by a directory tree and
> search DWG resources. It can be used to get the DataStoreParameters that are
> used to open an existing DWG creating a new DataStore or it also can be used
> to get the NewDataStoreParameters that are used to create a new DWG.
>
> DWGStoreParameters -> Defines the parameters that are needed to open a DWG
>
> DWGStoreProvider -> This provider is created from a DWGStoreParameters and
> it is able to read (or write) a DWG.
>
>
>
> After having implemented it, how can I register the provider with a plugin
> ?
>
>
> The project xxx.app.extension is the responsible to add a new plugin in
> gvSIG. It will contain the new provider.
>
>
> Which class among those provided by the plugin structure  should I use ?
>
> These are the classes:
>
> - A xxxManager: is the entry point to the API. Provides the main services
> of the library.
> - A xxxLocator: the responsible to provide access to the single Manager
> instance.
> - A xxxLibrary: initialization and configuration of the library.
> - A xxxService: another interface for the API. You may use it or not
> depending on your library's functionality.
>
> Well, it depends on any project. The Library class is normally located in
> all the projects, but the other classes will be contained depending on what
> are you developing. (e.g. extDWG is a DAL provider and it don't need any
> Manager)
>
> I Hope I clarify you some doubts.
>
> Regards,
> Jorge
>
>
> Thanks a lot for the help,
> Luca
>
>
> [1]
> http://www.gvsig.org/web/projects/gvsig-desktop/docs/devel/org.gvsig.fmap.dal/2.0.0/featurestore
> [2]
> http://www.gvsig.org/web/projects/gvsig-desktop/docs/devel/org.gvsig.fmap.dal/2.0.0/featurestore/consumer-services/creacion-de-un-nuevo-almacen
>
>
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>
>
>
> --
> Jorge Piera Llodrá
> gvSIG Development Team
> PRODEVELOP
> Plaza Don Juan de Villarrasa, 14 - 5
> 46001 Valencia
> Tel: +34 963510612
> Fax: +34 963510908
> e-mail: jpiera at prodevelop.eshttp://www.prodevelop.eshttp://www.gvsig.org
>
>
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