JPX

JPX is a Java library for creating, reading and writing GPS data in GPX format. It is a full implementation of version 1.1 and version 1.0 of the GPX format. The data classes are completely immutable and allows a functional programming style. They are working also nicely with the Java Stream API. It is also possible to convert the location information into strings which are compatible to the ISO 6709 standard.

Besides the basic functionality of reading and writing GPX files, the library also allows manipulating the read GPX object in a functional way.

Dependencies

No external dependencies are needed by the JPX library. It only needs Java 17 to compile and run. It also runs and compiles with Java 21.

Building JPX

For building the JPX library you have to check out the master branch from GitHub.

$ git clone https://github.com/jenetics/jpx.git

Executing the tests:

$ cd jpx
$ ./gradlew test

Building the library:

$ ./gradlew jar

Examples

Creating new GPX object with 3 track-points

final GPX gpx = GPX.builder()
    .addTrack(track -> track
        .addSegment(segment -> segment
        .addPoint(p -> p.lat(48.20100).lon(16.31651).ele(283))
        .addPoint(p -> p.lat(48.20112).lon(16.31639).ele(278))
        .addPoint(p -> p.lat(48.20126).lon(16.31601).ele(274))))
    .build();

Writing GPX object to a file

GPX.write(gpx, "track.gpx");

GPX output

<gpx version="1.1" creator="JPX - https://github.com/jenetics/jpx" xmlns="http://www.topografix.com/GPX/1/1">
    <trk>
        <trkseg>
            <trkpt lat="48.201" lon="16.31651">
                <ele>283</ele>
            </trkpt>
            <trkpt lat="48.20112" lon="16.31639">
                <ele>278</ele>
            </trkpt>
            <trkpt lat="48.20126" lon="16.31601">
                <ele>274</ele>
            </trkpt>
        </trkseg>
    </trk>
</gpx>

Reading GPX object from file

This example writes a given GPX object to a file, reads it again and prints the WayPoints of all tracks and all track-segments to the console.

GPX.write(gpx, "track.gpx");
GPX.read("gpx.xml").tracks()
    .flatMap(Track::segments)
    .flatMap(TrackSegment::points)
    .forEach(System.out::println);

Console output

$ [lat=48.201, lon=16.31651, ele=283]
$ [lat=48.20112, lon=16.31639, ele=278]
$ [lat=48.20126, lon=16.31601, ele=274]

Reading GPX extensions

The library is also able to read arbitrary GPX extensions.

<?xml version="1.0" encoding="UTF-8"?>
<gpx version="1.1" creator="JPX - Java GPX library" xmlns="http://www.topografix.com/GPX/1/1">
    ...
    <extensions>
        <gpxdata:lap xmlns:gpxdata="http://www.cluetrust.com/XML/GPXDATA/1/0">
            <gpxdata:index>1</gpxdata:index>
            <gpxdata:startPoint lat="51.219983" lon="6.765224"/>
            <gpxdata:endPoint lat="51.220137" lon="6.765098" />
        </gpxdata:lap>
    </extensions>
</gpx>

The extensions are available via a org.w3c.dom.Document object, with an extensions root element.

final Optional<Document> extensions = gpx.getExtensions();

Converting a GPX object into an org.w3c.dom.Document

final GPX gpx = ...;

final Document doc = XMLProvider.provider()
    .documentBuilderFactory()
    .newDocumentBuilder()
    .newDocument();

// The GPX data are written to the empty `doc` object.
GPX.Writer.DEFAULT.write(gpx, new DOMResult(doc));

Reading GPX 1.0 and writing GPX 1.1

By default, JPX is reading and writing the GPX files in version 1.1. But it is possible to read and write GPX files in version 1.0 as well.

// Reading GPX 1.0 file.
final GPX gpx10 = GPX.reader(GPX.Version.V10).read("track-v10.gpx");

// Changing GPX version to 1.1.
final GPX gpx11 = gpx10.toBuilder()
    .version(GPX.Version.V11)
    .build();

// Writing GPX to file.
GPX.write(gpx11, "track-v11.gpx");

ISO 6709 location strings

With the LocationFormatter class it is possible to create ISO 6709 compatible strings.

final Point p = WayPoint.of(...);
final Location loc = Location.of(p);
final LocationFormatter format = LocationFormatter.ISO_HUMAN_LONG;
System.out.println(format.format(loc));

The printed location will look like this

24°59'15.486"N 65°14'03.390"W 65.23m

It is also possible to define your own formatter from a given pattern string,

final LocationFormatter format = 
    LocationFormatter.ofPattern("DD°MMSS dd°mmss");

which leads to the following output

24°5915 65°1403

This string can then also be parsed to a location.

final Location location = format.parse("24°5915 65°1403");

Geodetic calculations

Distance between two points

final Point start = WayPoint.of(47.2692124, 11.4041024);
final Point end = WayPoint.of(47.3502, 11.70584);
final Length distance = Geoid.WGS84.distance(start, end);
System.out.println(distance);

Console output

$ 24528.356073554987 m

Path length

Calculate the path length of the first track-segment.

final Length length = gpx.tracks()
    .flatMap(Track::segments)
    .findFirst()
    .map(TrackSegment::points).orElse(Stream.empty())
    .collect(Geoid.WGS84.toPathLength());

GPX manipulation/filtering

Filtering

The following example filters empty tracks and track-segments from an existing GPX object.

final GPX gpx = GPX.read("track.gpx");

// Filtering empty tracks.
final GPX gpx1 = gpx.toBuilder()
    .trackFilter()
        .filter(Track::nonEmpty)
        .build()
    .build();

// Filtering empty track-segments.
final GPX gpx2 = gpx.toBuilder()
    .trackFilter()
        .map(track -> track.toBuilder()
            .filter(TrackSegment::nonEmpty)
            .build())
        .build()
    .build();

// Filtering empty tracks and track-segments.
final GPX gpx3 = gpx.toBuilder()
    .trackFilter()
        .map(track -> track.toBuilder()
            .filter(TrackSegment::nonEmpty)
            .build())
        .filter(Track::nonEmpty)
        .build()
    .build();

Changing GPX object

Fixing the time of all track way-points by adding one hour.

final GPX gpx = GPX.read("track.gpx");

final GPX gpx1 = gpx.toBuilder()
    .trackFilter()
        .map(track -> track.toBuilder()
            .map(segment -> segment.toBuilder()
                .map(wp -> wp.toBuilder()
                    .time(wp.getTime()
                        .map(t -> t.plusHours(1))
                        .orElse(null))
                    .build())
                .build())
            .build())
        .build()
    .build();

Doing the same only for the GPX way-points.

final GPX gpx = GPX.read("track.gpx");

final GPX gpx1 = gpx.toBuilder()
    .wayPointFilter()
        .map(wp -> wp.toBuilder()
            .time(wp.getTime()
                .map(t -> t.plusHours(1))
                .orElse(null))
            .build())
        .build()
    .build();

XML configuration

The JPX library uses the XML classes available in the Java java.xml module. This API is highly configurable and it is possible to replace the underlying implementation. Especially for Android, using different XML implementation is a necessity. JPX uses three factory classes for reading/writing GPX files:

1. XMLInputFactory: This class is needed for reading GPX files.
2. XMLOutputFactory: This class is needed for writing GPX files.
3. DocumentBuilderFactory: This class is used for creating XML-documents for the GPX extensions data.

You can change the used classes by implementing and registering a different XMLProvider class. The following code show how to change the configuration of the DocumentBuilderFactory class.

package org.acme;
final class ValidatingDocumentBuilder extends XMLProvider { 
    @Override
    public DocumentBuilderFactory documentBuilderFactory() { 
        final DocumentBuilderFactory factory = 
            DocumentBuilderFactory.newInstance();
        factory.setValidating(true);
        factory.setNamespaceAware(true);
        return factory; 
    }
}

And don't forget to create a META-INF/services/io.jenetics.jpx.XMLProvider file with the following content:

org.acme.NonValidatingDocumentBuilder

License

The library is licensed under the Apache License, Version 2.0.

Copyright 2016-2023 Franz Wilhelmstötter

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Release notes

3.1.0

Improvements

• #170: GPX files with invalid version number are now readable in LENIENT mode.

final GPX gpx;
try (InputStream in = new FileInputStream(resource)) {
	gpx = GPX.Reader.of(Mode.LENIENT).read(in);
}

Bugs

• #167: Fixing a test case for Windows.

3.0.1

Bugs

• #162: Elevation serialization for values > 1000m is incompatible with deserialization.

3.0.0

Improvements

• #125: Breaking change - Use Instant instead of ZonedDateTime for Point.time property.
• #148: Breaking change - Update to Java17.
• #155: Improved GPX.Reader and GPX.Writer classes.
• #158: Add XML Document reader/writer methods.

final GPX gpx = ...;

final Document doc = XMLProvider.provider()
    .documentBuilderFactory()
    .newDocumentBuilder()
    .newDocument();

// The GPX data are written to the empty `doc` object.
GPX.Writer.DEFAULT.write(gpx, new DOMResult(doc));

Bugs

• #151: Double's being written as exponents in GPX file.
• #152: LocationFormatter::parse method is not thread-safe.