Andrea,
Funny you bring this up, very timely as I've been looking at processes the
past few days.
On Fri, Jun 8, 2012 at 6:06 AM, Andrea Aime <andrea.a...@geo-solutions.it>wrote:
> Hi,
> writing processes over and over let me to see some deficiencies in the
> WPS annotations that
> I would like to clear out. Some are general to processes, some are WPS
> usage specific
> (that's why I'm cross posting to gs-devevl).
>
> One thing I see I do over and over at the start of a process is value
> defaulting and validation.
>
> For params that are not mandatory but have a default value, it would
> be nice to just stick
> the default value in the annotation:
>
> @DescribeParameter(name = "multiplier", min = 0, default = 1d) double
> multiplier
>
> For params that need validation it would be nice to have a set of
> common validators so that we don't
> have to roll the validation logic in the process code:
>
> @DescribeParameter(name = "myparam", validator = new
> RangeValidator(100, 200)) double myparam)
>
> I would really hate to have to roll our own in this case, there is
> plenty of validation packages
> around on the web, but all seem to be focusing quite specifically on a
> particular use case,
> e.g., validating forms, validating a Swing GUI, or carrying around a
> lot of extras. Sigh...
> I guess we could roll our own built on top of commons-validator
> routines, to avoid duplicating
> really everything? Or use some convention and reflection, something like:
>
> new Validator("double", "isInRange", 0, 100)
>
> to end up calling DoubleValidator.isInRange(value, min, max).
> Hmm... the above could be also done using code generation against all
> the routines to get a
> set of typesafe validation objects, or a factory exposing all the
> validators, Validators.doubleIsInRange(0, 100) -> Validator
>
> Moving on to something WPS specific, we need to be able to declare
> what mime types the input files/streams
> we are going to accept, and which ones we are going to produce.
> Normally we avoid this issue in GeoServer by trading objects (e.g.,
> RenderedImage, Coverage, FeatureCollection)
> that specialized utility classes (ProcessParameterIO) turn into a
> serialized format with a specific mime type.
> But there are processes around that really do trade files, and
> specific formats of them for what is worth.
>
> For files that are inputs we could have something like:
>
> @DescribeBinaryInput(..., mimeTypes = new String[] {image/png,
> image/jpeg, ...} ...)
>
> The mimeType would have then to be carried around by Parameter, which
> has a metadata map
> that we cannot read... can we add a getMetadata(key) method in there
> to access some random
> metadata?
>
> Dealing with the output formats instead is going to be loads of fun.
> We can have a
> @DescribeBinaryResult( ... mimeTypes = new String[] {image/png,
> image/jpeg, ...}
> and that would allow us to run DescribeProcess, but when it comes to
> executing the fun starts,
> since the user will choose one of the output formats as part of the
> _output_, not as part of
> the input:
>
> <wps:RawDataOutput mimeType="image/png">
> <ows:Identifier>theImage</ows:Identifier>
> </wps:RawDataOutput>
> </wps:ResponseForm>
>
> How is the process going to know that the user requested image/png as
> the output format, since
> that's not part of the inputs?
> All I can think if being explicit about which of the input params is
> going to be mapped to such choice,
> and avoid exposing such param in the DescribeProcess:
>
> @DescribeBinaryResult( ... mapToInput = "outputFormat")
> @DescribeParameter(name="outputFormat") String outputFormat
>
> Any better idea?
>
This one doesn't look terrible, from an implementer point of view it's
quite clear what it does.
>
> One final thing that happened to me while writing processes is
> realizing that a process
> will take long, that it cannot be written in a streaming manner for
> some reason, and thus
> really wanting the process to be only run in asynch mode.
> Ideally it would be nice to have the following:
>
> @DescribeProcess(... synch=false, asynch=true)
>
I really like this idea, and had been wondering about it. I'm not sure if
you want synch and asynch, perhaps only keep asynch with a default value of
false?
>
> However I don't see a way to expose this from ProcessFactory, and it's
> indeed something
> that would be pretty WPS specific. Maybe we should augment the
> ProcessFactory
> to return a open ended metadata map about the process?
>
> Map<String, Object> getProcessMetadata(Name process)
>
> Feedback welcomed.
>
> Cheers
> Andrea
>
>
> --
> Ing. Andrea Aime
> GeoSolutions S.A.S.
> Tech lead
>
> Via Poggio alle Viti 1187
> 55054 Massarosa (LU)
> Italy
>
> phone: +39 0584 962313
> fax: +39 0584 962313
> mob: +39 339 8844549
>
> http://www.geo-solutions.it
> http://geo-solutions.blogspot.com/
> http://www.youtube.com/user/GeoSolutionsIT
> http://www.linkedin.com/in/andreaaime
> http://twitter.com/geowolf
>
>
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