Martin,
The code we are using is found in
referencing->org.geotools.geometry->GeometryFactoryFinder.java and we
have begun adding the Hints constructors to PrimitiveFactoryImpl in the
unsupported gometry module.
Graham.
Martin Desruisseaux wrote:
> Jody Garnett a écrit :
>
>> In my understanding there are three steps:
>> 1- it needs the no argument constructor so that the FactorySPI system
>> can return an Object (if the user explicitly specified an exact
>> implementation it would be found and returned directly
>
>
> Yes. Note that the no-argument constructor is never invoked explicitly
> by org.geotools.factory.FactoryRegistry. It is invoked by
> javax.imageio.spi.ServiceRegistry.
>
>
>> 2- It would then ask the object for its class
>> 3- And then finally perform reflection on that class in order to look
>> for a constructor that creates hints
>
>
> There is a missing step:
>
> 2.5- It ask for Factory.getImplementationHints() and checks if the
> hints used by the Factory match the hints specified by the users.
>
>
>> Step 1 seems broken; when I commented out step 1 I was able to
>> confirm that step 2 and 3 work as expected.
>
>
> I'm not sure that it is broken; It seems to work with the referencing
> module, which uses many hints. Can you point me to a code I could look
> at?
>
>
>> We implemented the GeoTools Factory interface - it has the
>> getImplementationHints method and was suited for our purpose. Do you
>> really want us to extend the AbstractFactory?
>
>
> Right, you don't have to extends AbstractFactory. You can do as you
> wish as long as getImplementationHints() returns all relevant hints,
> but it must returns those hints (not an empty map). The hint must be
> declared even if its value is null. For example if a Factory cares
> about Hints.COORDINATE_REFERENCE_SYSTEM, then we must have something
> functionnaly equivalent to:
>
> public Map getImplementationHints() {
> Map hints = new HashMap();
> hints.put(Hints.COORDINATE_REFERENCE_SYSTEM, crs);
> return hints;
> }
>
> even if "crs" is null. Workflow example:
>
> * A user ask for a GeometryFactory with the following hints:
> userHints.put(Hints.COORDINATE_REFERENCE_SYSTEM, WGS_84);
>
> * FactoryRegistry scans for GeometryFactory in priority order. If
> it find a GeometryFactory of appropriate class (if a particular
> class was requested), it call its getImplementationHints() method.
> Then there is a choice:
>
> - If the getImplementationHints() do *not* contains a
> Hints.COORDINATE_REFERENCE_SYSTEM key (no matter if the associated
> value is null or not), then FactoryRegistry said "this factory
> don't
> care about the CRS. It is suitable for the user needs, since the
> user
> COORDINATE_REFERENCE_SYSTEM hint will not make any difference
> for this
> factory". No GeometryFactory(Hints) constructor is invoked since
> the
> existing factory is considered suitable and returned (as a cached
> factory).
>
> - If the getImplementationHints() do contains a
> Hints.COORDINATE_REFERENCE_SYSTEM key, then the value for this key
> is compared with the value provided in the "userHints" map. Then
> there
> is a choice:
>
> * If the values are equal (and assuming that all other relevant
> hints
> have been checked in the same way), then the GeometryFactory is
> considered suitable to user needs. No GeometryFactory(Hints)
> constructor is invoked since the existing factory is considered
> suitable and returned (as a cached factory).
>
> * If the values are not equal, then FactoryFinder continue the
> search
> for an other GeometryFactory. If no suitable GeometryFactory
> is found,
> then an exception is thrown. If we are actually using
> FactoryCreator
> instead of FactoryRegistry, only then the exception is caugh
> and a
> new factory is created using the GeometryFactory(Hints)
> constructor.
> This factory is then cached. Next time that a user will ask for a
> GeometryFactory, the new GeometryFactory just created will be one
> more candidate in the process described above.
>
> Martin
--
Graham Davis
Refractions Research Inc.
[EMAIL PROTECTED]
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