geoserver - Passing selected polygon to INTERSECTS filter in a WFS request

In the code below,

   

     
       the_geom
       
          sf:restricted
          the_geom
          cat = 3
       
     
   

I'd like to replace

   sf:restricted
   the_geom
   cat = 3

with a polygon selected by a user. I get the polygon from a selection event. I've tried a number of options, but none is working, yet. Any assistance will be highly appreciated.

My environment: GeoServer 2.1.3, OpenLayers 2.11.

---

I've transformed my geometry to EPSG:4326, the one used by my layers in GeoServer:

var geometry = event.feature.geometry.transform(new OpenLayers.Projection("900913"), new OpenLayers.Projection("EPSG:4326"));

The event.feature.geometry represents a polygon selected by a user. I've also converted the geometry to WKT format as shown below:

var wktParser = new OpenLayers.Format.WKT();
var feature = new OpenLayers.Feature.Vector();
feature.geometry = geometry;

var wktGeom = wktParser.write(feature);

I've then passed the geometry in WKT format to the filter as shown below:

'' +

'' +
    'the_geom' +
    '' +
        'ws:layer_2' +
        'the_geom' +
        'INTERSECTS(the_geom,' + wktGeom + ')' +
    '' +
'' +
'';

But when I send a request, the following error is returned:

Process failed during execution java.lang.ClassCastException: org.geotools.filter.AttributeExpressionImpl cannot be cast to org.opengis.filter.Filter org.geotools.filter.AttributeExpressionImpl cannot be cast to org.opengis.filter.Filter.

Any idea on what I may be doing wrong?

Answer

http://docs.geotools.org/latest/userguide/library/cql/cql.html

So the third parameter would be something like:

INTERSECTS(ATTR1, POLYGON((... )) )

The polygon has to be expressed in the WKT syntax and be in the same SRS as the layer being queried. Either that, or get a recent GeoServer version and call setSRS(POLYGON(...), 'EPSG:xywz') around the WKT (that function has been added May 27 so it should be in 2.1.4 but not earlier versions)