Add to WKT (Well-known Text) geometries a column computed using the Contextual Query Language

When your expression returns a numeric, Boolean or String result, you have to define the type of the column into which this results will be stored and the name of this column. If your expression returns a geometry, you can either process it as a geometry, and replace the original geometry; or store it as a String into a novel column.

Examples of queries:

• compute the area: "area(the_geom)"
• compute a centroid: "centroid(the_geom)"
• compute a buffer: "buffer(the_geom, 10)"
• compute the distance to a point defined by flow two Double flow variables x and y: "distance(the_geom,$${Dx}}$,$${Dy}}$)"

More examples can be found here: Geoserver ECQL Tutorial

Note that the units used in the query depend on the Coordinate Reference System.

The actual processing is done by the awesome geotools library.