wms - Use GetFeatureInfo with OpenLayers and a Bounding Polygon

I want to be able to draw a bounding polygon and have my MapServer WMS layer return every feature within that bounding box. I have it working for a single point, but I would like for the query to return every single feature within a polygon. Is that possible with WMS GetFeatureInfo? I am using OpenLayers in Java with GWT. There is a bridge between Java and the OpenLayers JS.

Answer

You cannot get information for features within a bbox using a WMS getFeatureInfo. Please have a look at the WMS reference for getFeatureInfo.

You will see that according to the standards, you can only pass in points, not a bbox.

Instead, you could use a getFeature Operation on the WFS service.

The BBOX parameter allows you to search for features that are contained (or partially contained) inside a box of user-defined coordinates. The format of the BBOX parameter is bbox=a1,b1,a2,b2wherea1, b1, a2, and b2 represent the coordinate values.

An example request involving returning features based on bounding box would be in the following format:

http://example.com/geoserver/wfs?
  service=wfs&
  version=2.0.0&
  request=GetFeature&
  typeName=namespace:featuretype&
  srsName=CRS
  bbox=a1,b1,a2,b2

(Please note, that I have linked to the geoserver site, instead of the actual OGC standards, as the Geoserver website is far more readable than the OGC standards.)