private Filter buildFilter(Envelope requestExtent, FilterFactory ffactory,
FeatureType schema) throws IllegalFilterException {
GeometryFilter bboxFilter;
bboxFilter = ffactory.createGeometryFilter(AbstractFilter.GEOMETRY_INTERSECTS);
BBoxExpression bboxExpr = ffactory.createBBoxExpression(requestExtent);
Expression geomAttExpr = ffactory.createAttributeExpression(schema,
schema.getDefaultGeometry().getName());
bboxFilter.addLeftGeometry(geomAttExpr);
bboxFilter.addRightGeometry(bboxExpr);