Extract polygons from shapefile using Geotools

4
votes

I have a shape file (Sample.shp) along with two other files (Sample.shx and Sample.dbf), which has geometry (polygons) defined for 15 pincodes of Bombay.

I am able to view the .shp file using the Quickstart tutorial. 

    File file = JFileDataStoreChooser.showOpenFile("shp", null);
    if (file == null) {
        return;
    }

    FileDataStore store = FileDataStoreFinder.getDataStore(file);
    SimpleFeatureSource featureSource = store.getFeatureSource();

    // Create a map content and add our shapefile to it
    MapContent map = new MapContent();
    map.setTitle("Quickstart");

    Style style = SLD.createSimpleStyle(featureSource.getSchema());
    Layer layer = new FeatureLayer(featureSource, style);
    map.addLayer(layer);

    // Now display the map
    JMapFrame.showMap(map);

Now I want to convert the geometry of these 15 pincodes to 15 Geometry/Polygon objects so that I can use Geometry.contains() to find if a point falls in a particular Geometry/Polygon.

I tried:

ShapefileReader r = new ShapefileReader(new ShpFiles(file),true,false,geometryFactory);
System.out.println(r.getCount(0)); >> returns 51
System.out.println(r.hasNext()); >> returns false

Any help is really appreciated

2
shapefilegeotools

2 Answers

1
votes

In fact you don't need to extract the geometries your self - just create a filter and iterate through the filtered collection. In your case there will probably be only one feature returned.

Filter pointInPolygon = CQL.toFilter("CONTAINS(the_geom, POINT(1 2))");
SimpleFeatureCollection features = source.getFeatures(filter);

    SimpleFeatureIterator iterator = features.features();
    try {
        while (iterator.hasNext()) {
            SimpleFeature feature = iterator.next();
            Geometry geom = (Geometry) feature.getDefaultGeometry();
           /*... do something here */
        }
    } finally {
        iterator.close(); // IMPORTANT
    }

For a full discussion of querying datastores see the Query Lab.

0
votes

I used the above solution and tried a few combinations. Just changed "THE_GEOM" to lower case and POINT is in order (Lon Lat)

Filter filter = CQL.toFilter("CONTAINS(the_geom, POINT(72.82916 18.942883))");
SimpleFeatureCollection collection=featureSource.getFeatures(filter);
SimpleFeatureIterator iterator = collection.features();

        try {
            while (iterator.hasNext()) {
                SimpleFeature feature = iterator.next();
                .....
            }
        } finally {
            iterator.close(); // IMPORTANT
        }