Question

I’m trying to parse a GPX file. I tried it with JDOM, but it does not work very well.

SAXBuilder builder = new SAXBuilder(); Document document = builder.build(filename); Element root = document.getRootElement(); System.out.println('Root:\t' + root.getName()); List<Element> listTrks = root.getChildren('trk'); System.out.println('Count trk:\t' + listTrks.size()); for (Element tmpTrk : listTrks) {   List<Element> listTrkpts = tmpTrk.getChildren('trkpt');   System.out.println('Count pts:\t' + listTrkpts.size());   for (Element tmpTrkpt : listTrkpts) {     System.out.println(tmpTrkpt.getAttributeValue('lat') + ':' + tmpTrkpt.getAttributeValue('lat'));   } } 

I opened the example file (CC-BY-SA OpenStreetMap) and the output is just:

Root: gpx
Count trk: 0

What can I do? Should I us a SAXParserFactory (javax.xml.parsers.SAXParserFactory) and implement a Handler class?

Answer 1

Here is my gpx reader. It ignores some of the tags but I hope it will help.

package ch.perry.rando.geocode;  import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.text.DateFormat; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.ArrayList; import java.util.Date; import java.util.List; import javax.xml.parsers.ParserConfigurationException; import javax.xml.parsers.SAXParser; import javax.xml.parsers.SAXParserFactory; import org.xml.sax.Attributes; import org.xml.sax.SAXException; import org.xml.sax.helpers.DefaultHandler;  /**  *  * @author perrym  */ public class GpxReader extends DefaultHandler {     private static final DateFormat TIME_FORMAT             = new SimpleDateFormat('yyyy-MM-dd'T'HH:mm:ss'Z'');      private List<Trackpoint> track = new ArrayList<Trackpoint>();     private StringBuffer buf = new StringBuffer();     private double lat;     private double lon;     private double ele;     private Date time;      public static Trackpoint[] readTrack(InputStream in) throws IOException {         try {             SAXParserFactory factory = SAXParserFactory.newInstance();             factory.setValidating(true);             SAXParser parser = factory.newSAXParser();             GpxReader reader = new GpxReader();             parser.parse(in, reader);             return reader.getTrack();         } catch (ParserConfigurationException e) {             throw new IOException(e.getMessage());         } catch (SAXException e) {             throw new IOException(e.getMessage());         }     }      public static Trackpoint[] readTrack(File file) throws IOException {         InputStream in = new FileInputStream(file);         try {             return readTrack(in);         } finally {             in.close();         }     }      @Override     public void startElement(String uri, String localName, String qName,             Attributes attributes) throws SAXException {         buf.setLength(0);         if (qName.equals('trkpt')) {             lat = Double.parseDouble(attributes.getValue('lat'));             lon = Double.parseDouble(attributes.getValue('lon'));         }     }      @Override     public void endElement(String uri, String localName, String qName)             throws SAXException {         if (qName.equals('trkpt')) {             track.add(Trackpoint.fromWGS84(lat, lon, ele, time));         } else if (qName.equals('ele')) {             ele = Double.parseDouble(buf.toString());         } else if (qName.equals('')) {             try {                 time = TIME_FORMAT.parse(buf.toString());             } catch (ParseException e) {                 throw new SAXException('Invalid time ' + buf.toString());             }         }     }      @Override     public void characters(char[] chars, int start, int length)             throws SAXException {         buf.append(chars, start, length);     }      private Trackpoint[] getTrack() {         return track.toArray(new Trackpoint[track.size()]);     } }