source: josm/src/org/openstreetmap/josm/io/RawGpsReader.java@ 64

package org.openstreetmap.josm.io;

import java.io.IOException;
import java.io.Reader;
import java.util.Collection;
import java.util.LinkedList;
import java.util.List;

import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.Namespace;
import org.jdom.input.SAXBuilder;
import org.openstreetmap.josm.data.GeoPoint;

/**
 * Read raw gps data from a gpx file. Only way points with their waies segments
 * and waypoints are imported.
 * @author imi
 */
public class RawGpsReader {

        /**
         * The data source from this reader.
         */
        public Reader source;
        
        /**
         * Construct a gps reader from an input reader source.
         * @param source The source to read the raw gps data from. The data must be
         *              in GPX format.
         */
        public RawGpsReader(Reader source) {
                this.source = source;
        }

        /**
         * The gpx namespace.
         */
        private Namespace GPX = Namespace.getNamespace("http://www.topografix.com/GPX/1/0");
        
        /**
         * Parse and return the read data
         */
        public Collection<Collection<GeoPoint>> parse() throws JDOMException, IOException {
                final SAXBuilder builder = new SAXBuilder();
                builder.setValidation(false);
                Element root = builder.build(source).getRootElement();
                return parseData(root);
        }

        /**
         * Parse and return the whole data thing.
         * @param root
         * @return
         */
        @SuppressWarnings("unchecked")
        private Collection<Collection<GeoPoint>> parseData(Element root) throws JDOMException {
                Collection<Collection<GeoPoint>> data = new LinkedList<Collection<GeoPoint>>();

                // workaround for bug where the server adds /gpx.asd to the namespace
                GPX = Namespace.getNamespace(root.getNamespaceURI());
                
                for (Object o : root.getChildren("wpt", GPX)) {
                        Collection<GeoPoint> line = new LinkedList<GeoPoint>();
                        line.add(new GeoPoint(parseDouble((Element)o, LatLon.lat), parseDouble((Element)o, LatLon.lon)));
                        data.add(line);
                }
                for (Object o : root.getChildren("rte", GPX)) {
                        Collection<GeoPoint> line = parseLine(((Element)o).getChildren("rtept", GPX));
                        if (!line.isEmpty())
                                data.add(line);
                }
                for (Object o : root.getChildren("trk", GPX)) {
                        for (Object seg : ((Element)o).getChildren("trkseg", GPX)) {
                                Collection<GeoPoint> line = parseLine(((Element)seg).getChildren("trkpt", GPX));
                                if (!line.isEmpty())
                                        data.add(line);
                        }
                }
                return data;
        }

        enum LatLon {lat, lon}
        /**
         * Return a parsed float value from the element behind the object o.
         * @param o An object of dynamic type org.jdom.Element (will be casted).
         * @param attr The name of the attribute.
         * @throws JDOMException If the absolute of the value is out of bound.
         */
        private double parseDouble(Element e, LatLon attr) throws JDOMException {
                double d = Double.parseDouble(e.getAttributeValue(attr.toString()));
                if (Math.abs(d) > (attr == LatLon.lat ? 90 : 180))
                        throw new JDOMException("Data error: "+attr+" value '"+d+"' is out of bound.");
                return d;
        }

        /**
         * Parse the list of waypoint - elements and return a collection with the
         * points read.
         */
        private Collection<GeoPoint> parseLine(List<Element> wpt) throws JDOMException {
                Collection<GeoPoint> data = new LinkedList<GeoPoint>();
                for (Element e : wpt)
                        data.add(new GeoPoint(parseDouble(e, LatLon.lat), parseDouble(e, LatLon.lon)));
                return data;
        }
}