Extract coordinates from KML file in Java

Question

I'm trying to parse a Kml file in Java. Cause I need to take the coordinates of a Placemark, to generate a poligon in java, and use it.

But my problem , is that i'm using JAK this library to parse it, and i'm not able to extract the information that i want.(I read the "help" in the official page, but I didn't found any help abut my problem)

I'm trying to do something like that:

final Kml kml = Kml.unmarshal(new File("C:/Users/A556520/Documents/Proyectos/GeoFencing/res/labasa.kml"));
final Document document = (Document)kml.getFeature();       
List<Feature> listafeatures = document.getFeature();        

But in this point I don't know how to extract the coordinates.

The file I'm trying to parse is this one: la basa

Answer 1

The answers above make use of the library de.micromata.opengis.kml which appears to be unsupported now. There is a newer library, OSM Bonus Pack which has a good KmlDocument class. I have used this to extract the coords as below. It only extracts lines (roads), not polygons, but it should be modifiable.

List<List<GeoPoint>> roads = new ArrayList<List<GeoPoint>>();

public void parseKmlDocument(KmlDocument doc) {
    int index = 0;
    for (KmlFeature kmlf: doc.mKmlRoot.mItems) {
        if ((kmlf instanceof KmlPlacemark))
        {
            KmlPlacemark placemark = (KmlPlacemark)kmlf;
            KmlGeometry kmlg = placemark.mGeometry;
            if (kmlg instanceof KmlMultiGeometry)
            {
                KmlMultiGeometry kmlmg = (KmlMultiGeometry)kmlg;
                for (KmlGeometry thisKmlg: kmlmg.mItems)
                {
                    ArrayList<GeoPoint> mCoordinates = thisKmlg.mCoordinates;
                    roads.add(index++, mCoordinates);

                }
            }
        }
        else {
                // kmlg is a LineString
                    ArrayList<GeoPoint> mCoordinates = kmlg.mCoordinates;
                    Road road = new Road(mCoordinates);
                    roads.add(road);
                    ++rIndex;
             
            }
    }
    // checking the result
    int road = 0 ;
    int gpoint = 0;
    for (List<GeoPoint> listGp: roads) {
        Log.d("road ", String.valueOf(road++));
        for (GeoPoint gp: listGp) {
            gpoint++;
            Log.d("    coords ",gp.getLatitude() + " " + gp.getLongitude());
        }
    }
    Log.d("Summary ",road + " roads containing " + gpoint + " geopoints");
}

Answer 2

With respect to A4L answer , thank you so much while i have added some more extraction methods which will get data from folder and document with point line and polygon extraction with spring MVC using javaapi4kml using package

<dependency>
<groupId>de.micromata.jak</groupId>
<artifactId>JavaAPIforKml</artifactId>
<version>2.2.0</version>
</dependency> 

@RequestMapping(value = "/testKml", method = RequestMethod.POST)
public Map<String, Object> parseKml(@RequestBody Map<String, Object> data){
    Map<String, Object> response = new HashMap<String, Object>();
    List<Map<String, Object>> wktObjrow = new ArrayList<Map<String, Object>>();
    String src = data.get("kmlfile").toString();
    try {
        URL url;
        url = new URL(src);
        URLConnection conn = url.openConnection();
        InputStream is = url.openStream();
        Assert.notNull(is);
        Kml kml = Kml.unmarshal(is);
        Feature feature = kml.getFeature();
        Map<String, Object> geodata = new HashMap<String, Object>();

        if(feature != null) {
            if(feature instanceof Document) {
                Document document = (Document) feature;
                List<Feature> featureList = document.getFeature();
                for(Feature documentFeature : featureList) {
                    if(documentFeature instanceof Placemark) {
                        geodata = new HashMap<String, Object>();
                        Placemark placemark = (Placemark) documentFeature;
                        Geometry geometry = placemark.getGeometry();
                        geodata = parseGeometry(geometry, documentFeature.getName().toString());
                        if(!geodata.isEmpty())
                        {
                            wktObjrow.add(geodata);
                        }
                    }
                    else if(documentFeature instanceof Folder) 
                    {
                        Folder folder = (Folder) documentFeature;
                        List<Feature> folderfeaturList = folder.getFeature();
                        for(Feature folderfeature : folderfeaturList) 
                        {
                            geodata = new HashMap<String, Object>();
                            if(folderfeature instanceof Placemark) {
                                Placemark placemark = (Placemark) folderfeature;
                                Geometry geometry = placemark.getGeometry();
                                //push each of return store in list
                                geodata = parseGeometry(geometry, placemark.getName().toString());
                                if(!geodata.isEmpty())
                                {
                                    wktObjrow.add(geodata);
                                }
                            }
                            else
                            {
                                System.err.println("folderfeatures was not of type Placemark"); 
                            }
                        }
                    }
                    else
                    {
                        System.err.println("Was not instance of Placemark or Folder");
                    }
                }
                System.out.println("wktObjrow : "+wktObjrow);
            }
            else
            {
                System.err.println("instance of feature was Not Document");
                if(feature instanceof Folder) {
                    Folder folder = (Folder) feature;
                    List<Feature> featureList = folder.getFeature();

                    geodata = new HashMap<String, Object>();

                    for(Feature documentFeature : featureList) {

                        if(documentFeature instanceof Placemark) {
                            Placemark placemark = (Placemark) documentFeature;
                            Geometry geometry = placemark.getGeometry();
                            if(documentFeature.getName().toString().length() > 0)
                            {
                                geodata =  parseGeometry(geometry, documentFeature.getName().toString());
                                if(!geodata.isEmpty())
                                {
                                    wktObjrow.add(geodata);
                                }
                            }
                            else 
                            {
                                geodata = parseGeometry(geometry, placemark.getName().toString());
                                if(!geodata.isEmpty())
                                {
                                    wktObjrow.add(geodata);
                                }
                            }

                        }else
                        {
                            System.err.println("Was not instance of Placemark");
                        }
                    }
                    System.out.println("wktObjrow : "+wktObjrow);

                }
            }
        }
        else
        {
            System.err.println("Feature was null");
            response.put("Null", "Feature was null");
        }
    }
    catch (Exception e) {
        // TODO: handle exception
        System.err.println("Exception @ : "+ e);
    }

    if(!wktObjrow.isEmpty() && wktObjrow != null)
    {
        response.put("data", wktObjrow);
    }

    return response;
}

public Map<String, Object> parseGeometry(Geometry geometry,String name) {
    // <Point> <LinearRing> <Geometry> <Model> <LineString> <Polygon> <MultiGeometry>

    Map<String, Object> response = new HashMap<String, Object>();
    List<Map<String, Object>> wktObjrow = new ArrayList<Map<String, Object>>();

    if(geometry != null) {
        if(geometry instanceof Polygon) {
            Polygon polygon = (Polygon) geometry;
            Boundary outerBoundaryIs = polygon.getOuterBoundaryIs();
            if(outerBoundaryIs != null) {
                LinearRing linearRing = outerBoundaryIs.getLinearRing();
                if(linearRing != null) {
                    List<Coordinate> coordinates = linearRing.getCoordinates();
                    if(coordinates != null) {
                        Map<String, Object> map = new HashMap<String, Object>();
                        ArrayList<String> wkt_lonlat = new ArrayList<String>();
                        for(Coordinate coordinate : coordinates) {
                            wkt_lonlat.add(coordinate.getLongitude()+" "+coordinate.getLatitude());
                        }
                        response.put("name",name);
                        response.put("category","POLYGON");
                        response.put("row","POLYGON(("+String.join(",", wkt_lonlat)+"))");
                    }
                    else
                    {
                        System.err.println("coordinate was null");
                    }
                }
            }
        }
        else if(geometry instanceof Point)
        {
            Point point = (Point) geometry;
            List<Coordinate> coordinates = point.getCoordinates();
            if(coordinates != null  && !coordinates.isEmpty())
            {
                if(coordinates != null) {

                    for(Coordinate coordinate : coordinates) {
                        Map<String, Object> map = new HashMap<String, Object>();
                        response.put("lon",coordinate.getLongitude());
                        response.put("lat",coordinate.getLatitude());
                        response.put("name",name);
                        response.put("category","POINT");
                    }
                }
            }
        }
        else if(geometry instanceof LineString)
        {
            LineString line = (LineString) geometry;
            List<Coordinate> coordinates = line.getCoordinates();
            if(coordinates != null  && !coordinates.isEmpty())
            {
                if(coordinates != null) {
                    Map<String, Object> map = new HashMap<String, Object>();
                    ArrayList<String> wkt_lonlat = new ArrayList<String>();
                    for(Coordinate coordinate : coordinates) {
                        wkt_lonlat.add(coordinate.getLongitude()+" "+coordinate.getLatitude());
                    }
                    response.put("name",name);
                    response.put("category","LINESTRING");
                    response.put("row","LINESTRING("+String.join(",", wkt_lonlat)+")");
                }
            }
       }
       else if(geometry instanceof MultiGeometry)
       {

            MultiGeometry multigeometry = (MultiGeometry) geometry;
               for (int j = 0; j < multigeometry.getGeometry().size(); j++) {
                    if(multigeometry.getGeometry().get(j) instanceof LineString)
                    {
                        LineString line = (LineString) multigeometry.getGeometry().get(j);
                        List<Coordinate> coordinates = line.getCoordinates();
                        if(coordinates != null  && !coordinates.isEmpty())
                        {
                            if(coordinates != null) {
                                Map<String, Object> map = new HashMap<String, Object>();

                                ArrayList<String> wkt_lonlat = new ArrayList<String>();

                                for(Coordinate coordinate : coordinates) {
                                    wkt_lonlat.add(coordinate.getLongitude()+" "+coordinate.getLatitude());
                                }
                                response.put("name",name);
                                response.put("category","LINESTRING");
                                response.put("row","LINESTRING("+String.join(",", wkt_lonlat)+")");
                            }
                        }
                    }
                    else if(multigeometry.getGeometry().get(j) instanceof Point)
                    {
                        Point point = (Point) multigeometry.getGeometry().get(j);
                        List<Coordinate> coordinates = point.getCoordinates();
                           if(coordinates != null  && !coordinates.isEmpty())
                           {
                               if(coordinates != null) {
                                   for(Coordinate coordinate : coordinates) {
                                    Map<String, Object> map = new HashMap<String, Object>();
                                    response.put("lon",coordinate.getLongitude());
                                    response.put("lat",coordinate.getLatitude());
                                    response.put("name",name);
                                    response.put("category","POINT");
                                   }
                               }
                           }
                    }
                    else if(multigeometry.getGeometry().get(j) instanceof Polygon)
                    {
                        Polygon polygon = (Polygon) multigeometry.getGeometry().get(j);
                        Boundary outerBoundaryIs = polygon.getOuterBoundaryIs();
                        if(outerBoundaryIs != null) {
                            LinearRing linearRing = outerBoundaryIs.getLinearRing();
                            if(linearRing != null) {
                                List<Coordinate> coordinates = linearRing.getCoordinates();
                                if(coordinates != null) {

                                    Map<String, Object> map = new HashMap<String, Object>();

                                    ArrayList<String> wkt_lonlat = new ArrayList<String>();

                                    for(Coordinate coordinate : coordinates) {
                                        wkt_lonlat.add(coordinate.getLongitude()+" "+coordinate.getLatitude());
                                    }
                                    response.put("name",name);
                                    response.put("category","POLYGON");
                                    response.put("row","POLYGON(("+String.join(",", wkt_lonlat)+"))");
                                }
                                else
                                {
                                    System.err.println("coordinate was null");
                                }
                            }
                        }
                    }
               }

       }
    }
    else
    {
        System.err.println("geometry was null");
        response.put("Null", "geometry was null");
    }
    return response;
}

Answer 3

Following the javadocs (unofficial) you need to check - using instanceof - each Feature whether is is a Placemark, if yes cast to it and get the Geometry which itself needs to be checked whether it is a Polygon, if yes then cast to it. After that the path to the coordinates is the following (just as it come in the kml-file):

getOuterBoundaryIs > getlinearRing > getCoordinates

Here is how it looks like in code:

@Test
public void parseKml() {
    String src = "misctests/stackoverflow/kml/labasa.kml";
    try(InputStream is = getClass().getClassLoader().getResourceAsStream(src)) {
        Assert.assertNotNull(is);
        Kml kml = Kml.unmarshal(is);
        Feature feature = kml.getFeature();
        parseFeature(feature);
    }
}

private void parseFeature(Feature feature) {
    if(feature != null) {
        if(feature instanceof Document) {
            Document document = (Document) feature;
            List<Feature> featureList = document.getFeature();
            for(Feature documentFeature : featureList) {
                if(documentFeature instanceof Placemark) {
                    Placemark placemark = (Placemark) documentFeature;
                    Geometry geometry = placemark.getGeometry();
                    parseGeometry(geometry);
                }
            }
        }
    }
}

private void parseGeometry(Geometry geometry) {
    if(geometry != null) {
        if(geometry instanceof Polygon) {
            Polygon polygon = (Polygon) geometry;
            Boundary outerBoundaryIs = polygon.getOuterBoundaryIs();
            if(outerBoundaryIs != null) {
                LinearRing linearRing = outerBoundaryIs.getLinearRing();
                if(linearRing != null) {
                    List<Coordinate> coordinates = linearRing.getCoordinates();
                    if(coordinates != null) {
                        for(Coordinate coordinate : coordinates) {
                            parseCoordinate(coordinate);
                        }
                    }
                }
            }
        }
    }
}

private void parseCoordinate(Coordinate coordinate) {
    if(coordinate != null) {
        System.out.println("Longitude: " +  coordinate.getLongitude());
        System.out.println("Latitude : " +  coordinate.getLatitude());
        System.out.println("Altitude : " +  coordinate.getAltitude());
        System.out.println("");
    }
}

Answer 4

Thanks @A4L This is really an update and a more groovier way of doing the same So changed for Groovy and also attempts more types than the example given as well digs deep within a document layer:

 /**
     * This starts the process and reads in the uk file
     */
    public static void parseKml() {
        def src = ServletContextHolder.servletContext.getRealPath("/KML/doc.kml")
        InputStream is = new FileInputStream(src);
        Kml kml = Kml.unmarshal(is);
        Feature feature = kml.getFeature();
        parseFeature(feature);
    }

    /**
     * This is step 2 of the process it figures out if it has a direct placemark mapping on kml
     * or if this is part of some big folder structure
     * @param feature
     */
    public static void parseFeature(Feature feature) {
        if(feature) {
            if(feature instanceof Document) {
                feature?.feature?.each { documentFeature->
                    if(documentFeature instanceof Placemark) {
                        getPlacemark((Placemark) documentFeature)
                    } else if (documentFeature instanceof Folder) {
                        getFeatureList(documentFeature.feature)
                    }
                }
            }
        }
    }


    /**
     * This iterates over itself over and over again to gain access to placemarks within folders
     * The uk map boundary was nested folders within folders
     * @param features
     * @return
     */
    public static List<Feature> getFeatureList(List<Feature> features) {
        features?.each { Feature  f ->
            if (f instanceof Folder) {
                getFeatureList(f.getFeature())
            } else if (f instanceof Placemark) {
                getPlacemark((Placemark) f)
            }
        }
    }

    /**
     * This in short kicks off looking at a placemark it's name then parsing through each of its geometry points
     * This controls the listener content or should I say builds it up from within this helper
     * @param placemark
     */
    public static void getPlacemark(Placemark placemark) {
        Geometry geometry = placemark.getGeometry()
        List results = parseGeometry(geometry)
        GeoMapListener.update(placemark.name, results)
    }


    private static List parseGeometry(Geometry geometry) {
        List results=[]
        if(geometry != null) {
            if(geometry instanceof Polygon) {
                Polygon polygon = (Polygon) geometry;
                Boundary outerBoundaryIs = polygon.getOuterBoundaryIs();
                if(outerBoundaryIs != null) {
                    LinearRing linearRing = outerBoundaryIs.getLinearRing();
                    if(linearRing != null) {
                        List<Coordinate> coordinates = linearRing.getCoordinates();
                        if(coordinates != null) {
                            for(Coordinate coordinate : coordinates) {
                                results << parseCoordinate(coordinate);
                            }
                        }
                    }
                }
            } else  if (geometry instanceof LineString) {
                LineString lineString = (LineString) geometry;
                List<Coordinate> coordinates = lineString.getCoordinates();
                if (coordinates != null) {
                    for (Coordinate coordinate : coordinates) {
                        results <<  parseCoordinate(coordinate);
                    }
                }
            }
        }
        return results
    }

    private static Map parseCoordinate(Coordinate coordinate) {
        Map results=[:]
        if(coordinate) {
            results.longitude= coordinate.longitude
            results.latitude= coordinate.latitude
            results.altitude= coordinate.altitude
        }
        return results
    }

Answer 5

Came across this post, so here is part of the code of function I have been using in my app to extract Place mark name & coordinates from a String kmlText.

    if (kmlText != null & kmlText.length() > 0) {
    // Change case of relevant tags to match our search string case
    kmlText = kmlText.replaceAll("(?i)<Placemark>", "<Placemark>")
        .replaceAll("(?i)</Placemark>", "</Placemark>")
        .replaceAll("(?i)<name>", "<name>")
        .replaceAll("(?i)</name>", "</name>")
        .replaceAll("(?i)<coordinates>", "<coordinates>")
        .replaceAll("(?i)</coordinates>", "</coordinates>");
    // Get <Placemark> tag
    String[] kmlPlacemarks = kmlText.split("</Placemark>");
    if (kmlPlacemarks.length > 0) {
        for (Integer i = 0; i < kmlPlacemarks.length; i++) {
            // Add '</Placemark>' to the end - actually not necessary
            kmlPlacemarks[i] += "</Placemark>";
            if (kmlPlacemarks[i].indexOf("<Placemark>") > -1)
                /* Trim front to start from '<Placemark>'
                Otherwise additional tags may be in between leading
                to parsing of incorrect values especially Name */
                kmlPlacemarks[i] = kmlPlacemarks[i].substring(kmlPlacemarks[i].indexOf("<Placemark>"));
        }
        String tmpPlacemarkName;
        String tmpPlacemarkCoordinates;
        for (String kmlPlacemark: kmlPlacemarks)
            if ((kmlPlacemark.indexOf("<name>") > -1 && kmlPlacemark.indexOf("</name>") > -1) &&
                    (kmlPlacemark.indexOf("<coordinates>") > -1 && kmlPlacemark.indexOf("</coordinates>") > -1)) {
                tmpPlacemarkCoordinates = kmlPlacemark.substring(kmlPlacemark.indexOf("<coordinates>") + 13, kmlPlacemark.indexOf("</coordinates>"));
                tmpPlacemarkName = kmlPlacemark.substring(kmlPlacemark.indexOf("<name>") + 6, kmlPlacemark.indexOf("</name>"));
            }
        }
}