A couple things Steve:
The CQL code is pretty generic - it just parses out a GeoTools Filter
object. ECQL is our custom extension of CQL that offers a better reflection
of what our Filter object can do. As an example CQL can compare a property
name to an expression, while ECQL can compare two expressions.
There is no difference to the data structure if you create it with a
FilterFactory or an ECQL expression.
The Filter data structure has two places you can extend it:
- Function - create your own function following the tutorial in the user
guide
- PropertyAccessor - teach filter how to extract values out of your objects
(GeoTools does Features, other applications do java beans, or
java.util.Map, or whatever ....).
FilterVisitor is used to process your expression once it is written. A very
simple process is to evaluate to a value. A more complicated one would be
to simplify or refactor an expression ... or to generate SQL.
Jody
--
Jody Garnett
On 15 March 2015 at 09:54, Stephen Brooke <sbro...@mdacorporation.com>
wrote:
> Hi list,
>
>
>
> I am thinking of using CQL as a filter language in my own application and
> I’ve been looking at “gt-cql.jar” in the GeoTools suite of tools as a
> library to do the heavy lifting. However, I’m having trouble knowing where
> to start.
>
>
>
> The scenario I am trying to implement is as follows:
>
> A user creates a rule for how they want to receive notifications about new
> data available and the rule can contain a filter which I send to my
> application as a CQL filter. The application stores the rule and when “new
> data available” event occurs the application needs to go through all user
> rules and determine whether notifications need to be sent to which users.
> So the application needs to go through each rule and see which ones are a
> match for the “new data available” event.
>
>
>
> Does anyone have any pointers as to where to start if I want to use
> GeoTools to help with this?
>
>
>
> The classes I’ve studied so far are:
>
> org.geoserver.wfs.GetFeature
>
> org.geoserver.wfs.JoinExtractingVisitor
>
> org.geoserver.monitor.FilterVisitorSupport
>
> org.geotools.filter.FilterFactoryImpl
>
> org.opengis.filter.Filter
>
> org.geoserver.ows.KvpParser
>
> org.geotools.filter.text.cql2.CQLTest
>
> org.geotools.filter.text.cql2.CQL
>
>
>
> --Steve
>
>
>
>
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