Filtering and Extracting vector data

WFS also defines mechanisms to only retrieve a subset of the data that matches some specified constraints.

1. Create a new request.xml file in the training root and past the following request into it:

   <wfs:GetFeature xmlns:wfs='http://www.opengis.net/wfs'
     xmlns:ogc='http://www.opengis.net/ogc' service='WFS' version='1.0.0'>
     <Query typeName='geosolutions:WorldCountries'>
       <ogc:Filter>
         <ogc:FeatureId fid='WorldCountries.137' />
       </ogc:Filter>
     </Query>
   </wfs:GetFeature>
   

2. Go on the command line, move to the training folder root, and execute the request using CURL:

   curl -XPOST -d @request.xml -H "Content-type: application/xml" "http://localhost:8083/geoserver/ows"
   

   Tip

   The gdal.bat script can be used to run a prompt with cUrl in its path. Type cd.. to go into the <TRAINING_ROOT> directory.

3. Now, let’s write an equivalent request - using the name of a state instead of the id- issuing a GET and encoding the filter in a language called CQL. Copy the following URL in your browser’s navigation bar:

   http://localhost:8083/geoserver/wfs?request=GetFeature&service=WFS&version=1.0.0&typeName=geosolutions:WorldCountries&outputFormat=GML2&CQL_FILTER=NAME=%27Monaco%27
   

   

   The CQL filter in the Firefox URL bar

   

   The results of the CQL filter

That’s how a feature set is filtered with either the OGC encoding or the CQL notation.

In the next section we will see how to edit the features via a protocol called WFS Transactional (WFS-T).