On Mon, Sep 21, 2020 at 11:08 AM Erwan Bocher <erwan.boc...@univ-ubs.fr>
wrote:
> I'd like to apply more complex expressions as the Case When above. It
> seems there is a function closed to the SQL Case When called if_then_else.
>
> So I try :
>
> Expression expression =
> ECQL.toExpression("if_then_else(area(THE_GEOM)>10,5, 1)");
>
> definitions.add(new Definition("EXP", expression));
>
> SimpleFeatureSource transformed =
> TransformFactory.transform((SimpleFeatureSource) fs,
> "OUTPUT_TABLE_TEST_F", definitions);
>
> Unfortunately, it returns the following exception
>
> Exception in thread "main" org.geotools.filter.text.cql2.CQLException:
> Encountered ">" at line 1, column 28.
>
> Is there a way to execute nested expression with Geotools ECQL parser ?
>
It is, but you're mixing filters and expressions in the wrong way. Filters
use expressions, but
they are not expressions. So something like "area(THE_GEOM)>10" is a
filter, it cannot
be nested inside an expression, only inside another filter.
There are filter functions that try to work around this limitation, so you
could write this instead:
if_then_else(greater(area(THE_GEOM), 10),5, 1)
I'd love to see an improvement in GeoTools allowing to treat a Filter like
an Expression that returns
a boolean but... the change would not be trivial, and rife with
repercussions (would allow building
filters/expressions that are not valid anymore, not in CQL, nor in Filter
Encoding).
Cheers
Andrea
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