How to parse KML data using geotools?

Question

Geotools contains some packages dealing with KML: org.geotools.kml and org.geotools.kml.bindings. I assume it was designed to parse KML data.

Do you know how to use it?

Answer 1

The KML support is tied into the XML facilities for encoding and parsing geometry.

The GeoTools user guide has replaced the wiki links provided by Ian above - with a nice clear page devoted to wrangling geometry and XML:

http://docs.geotools.org/latest/userguide/library/xml/geometry.html

One of the headings on that page is devoted to KML (http://docs.geotools.org/latest/userguide/library/xml/geometry.html#kml).

Site policy here asks that we include the answer rather than just provide links. With that in mind:

Encoder encoder = new Encoder(new KMLConfiguration());
encoder.setIndenting(true);

encoder.encode(featureCollection, KML.kml, outputstream );

Or to parse KML you need to consider geometry and style as KML includes both. Here is an example that fetches a collection of features back.

Parser parser = new Parser(new KMLConfiguration());
SimpleFeature f = (SimpleFeature) parser.parse( inputStream );
Collection placemarks = (Collection) f.getAttribute("Feature");

You can also ask it for a stream of results (incase the file is bigger than memory):

StreamingParser parser = new StreamingParser( inputStream, KML.Placemark);
SimpleFeature f = null;

while ((f = (SimpleFeature) parser.parse()) != null) {
    FeatureTypeStyle style = (FeatureTypeStyle) f.getAttribute("Style");

    Symbolizer[] syms = style.getRules()[0].getSymbolizers();
    assertEquals(3, syms.length);

    count++;
}

Best of luck (and if in doubt review the test cases).

Answer 2

There is a KMLExample at http://svn.osgeo.org/geotools/trunk/demo/example/src/main/java/org/geotools/demo/xml/KMLExample.java which shows the KML bindings in use for writing. From other discussions on the user list it seems that the KML bindings work in a similar way to the GML bindings so look at http://docs.codehaus.org/display/GEOTDOC/GML+XML+Support for more clues.

When you get a solution feel free to post it to the GeoTools wiki.