Parse GeoJSON file with Java Topology Suite or GeoTools

Question

For example, if you have a GeoJSON file like this with a polygon(simple file for the test)

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              -4.658203125,
              41.343824581185686
            ],
            [
              -5.6689453125,
              39.13006024213511
            ],
            [
              -1.9335937499999998,
              39.16414104768742
            ],
            [
              -1.3623046875,
              41.21172151054787
            ],
            [
              -4.658203125,
              41.343824581185686
            ]
          ]
        ]
      }
    }
  ]
}

The point:

Geometry point2 = new WKTReader().read("POINT (-3.2958984375 40.44694705960048)");

And you want to load the geoJSON file in your program to test in this polygon contains the point, how could you do it in Java using JTS?

Other option could be use GeoTools with GeoJson plugin but i'm not able to parse a GeoJson file

What I have tried

Using GEOTOOLS like this

String content = new String(Files.readAllBytes(Paths.get("file.geojson")), "UTF-8");
GeometryJSON gjson = new GeometryJSON();
Reader reader = new StringReader(content);
Polygon p = gjson.readPolygon(reader);
System.out.println("polygon: " + p);

The problem here is that polygon p only contains the last polygon of the geojson file. If this file have many polygons, how should I parse it?

Using JTS2GEOJSON like this

String content = new String(Files.readAllBytes(Paths.get("file.geojson")), "UTF-8");
System.out.println("content: " + content);
GeoJSONReader reader1 = new GeoJSONReader();
Geometry geometry = reader1.read(content);

This code fail is this line:

Geometry geometry = reader1.read(content);

With this error:

Exception in thread "main" java.lang.UnsupportedOperationException
    at org.wololo.jts2geojson.GeoJSONReader.read(GeoJSONReader.java:51)
    at org.wololo.jts2geojson.GeoJSONReader.read(GeoJSONReader.java:21)
    at org.wololo.jts2geojson.GeoJSONReader.read(GeoJSONReader.java:16)

This error is due i'm trying to read a FeatureCollections from GeoJson file. It works if I tried with this simple string:

   String content = "{\n" +
                "        \"type\": \"Polygon\",\n" +
                "        \"coordinates\": [\n" +
                "          [\n" +
                "            [\n" +
                "              -4.141845703125,\n" +
                "              40.9218144123785\n" +
                "            ],\n" +
                "            [\n" +
                "              -4.603271484375,\n" +
                "              40.002371935876475\n" +
                "            ],\n" +
                "            [\n" +
                "              -3.5595703125,\n" +
                "              39.757879992021756\n" +
                "            ],\n" +
                "            [\n" +
                "              -2.548828125,\n" +
                "              40.43858586704331\n" +
                "            ],\n" +
                "            [\n" +
                "              -3.2080078125,\n" +
                "              41.12074559016745\n" +
                "            ],\n" +
                "            [\n" +
                "              -4.141845703125,\n" +
                "              40.9218144123785\n" +
                "            ]\n" +
                "          ]\n" +
                "        ]\n" +
                "      }";

What have you tried so far? – Ian Turton Dec 28 '18 at 18:06 — Ian Turton, Dec 28 '18 at 18:06
I added more details in the main post @IanTurton – IoT user Jan 08 '19 at 09:19 — IoT user, Jan 08 '19 at 09:19

Ian Turton · Accepted Answer · 2019-01-08T11:54:49.127

7

If you are using GeoTools then you need to start thinking in terms of DataStores and FeatureCollections. There is lots of built in smarts (much of it using JTS) to handle filtering etc which saves you a lot if potential issues.

File inFile = new File("/home/ian/Data/states/states.geojson");
Map<String, Object> params = new HashMap<>();
params.put(GeoJSONDataStoreFactory.URLP.key, URLs.fileToUrl(inFile));
DataStore newDataStore = DataStoreFinder.getDataStore(params);
String pt = "POINT (-107 42)";

FilterFactory2 ff = CommonFactoryFinder.getFilterFactory2();
SimpleFeatureSource featureSource = newDataStore.getFeatureSource(newDataStore.getTypeNames()[0]);
Filter f = ff.contains(ff.property(featureSource.getSchema().getGeometryDescriptor().getLocalName()),
    ff.literal(pt));
SimpleFeatureCollection collection = featureSource.getFeatures(f);
if (collection.size() > 0) {
  try (SimpleFeatureIterator itr = collection.features()) {
    while (itr.hasNext()) {
      System.out.println(itr.next());
    }
  }
}

This will need the following in your pom.xml:

<dependency>
   <groupId>org.geotools</groupId>
   <artifactId>gt-geojsondatastore</artifactId>
   <version>${geotools.version}</version>
</dependency>
<dependency>
   <groupId>org.geotools</groupId>
   <artifactId>gt-shapefile</artifactId>
   <version>${geotools.version}</version>
 </dependency>

edited Jan 08 '19 at 11:54

answered Jan 08 '19 at 09:36

Ian Turton

10,018
1
28
47

it would be possible to do it using an InputStream inFile instead of File inFile? I have tried but it doesn't work here: `URLs.fileToUrl(inFile)` The way I've done is read from InputStream, create a temporary file and copy to to him but if I run this code in AWS it fails and I think is due to create a file (because in local run without problem) – IoT user Jan 14 '19 at 15:10
No, you need either a real URL or a file converted to a URL. May be using java.tempfile might help? – Ian Turton Jan 14 '19 at 15:13
That is what we are using: `File tempFile = File.createTempFile("prefix-", ".geojson"); tempFile.deleteOnExit();` and if I run it locally with apache Flink all works well. The problem is when I run it in Kinesis Data Analytics no error have been shown but the method doesn't work because I don't have any result – IoT user Jan 14 '19 at 16:50
I think this is probably going to be a new question for AWS experts - all I can suggest is checking the file exists in the code? – Ian Turton Jan 14 '19 at 17:08
Hi @IanTurton, would you help me with this question? https://gis.stackexchange.com/q/330030/146554 – Felipe Jul 26 '19 at 08:19
GeoJSONDataStoreFactory <- what is this ? – Adelin May 26 '21 at 12:23
A factory for creating `GeoJSONDataStore`s? – Ian Turton May 26 '21 at 12:32

score 2 · Answer 2 · answered Dec 31 '18 at 04:20

2

With the GeoJsonReader class you can read a GeoJson Geometry from a JSON fragment into a Geometry:

http://locationtech.github.io/jts/javadoc/org/locationtech/jts/io/geojson/GeoJsonReader.html

Then, test whether that geometry (geojson polygon) contains the argument geometry (wkt point):

http://locationtech.github.io/jts/javadoc/org/locationtech/jts/geom/Geometry.html#contains(org.locationtech.jts.geom.Geometry)

answered Dec 31 '18 at 04:20

LuisTavares

2,146
2
12
18

2

how should I use the GeoJSONReader according to my code added at the main post? – IoT user Jan 08 '19 at 09:20

Parse GeoJSON file with Java Topology Suite or GeoTools

2 Answers2

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