GeoTools Geometries lost when storing features to shapefile

Question

As you know, the geometry column name of schema for saving into a shapefile must be "the_geom". I have a SimpleFeatureCollection with a schema, geometry name of which is not "the_geom"; It is "geometry". I want to save this collection into an esri shapefile. But I loose geoemetries when storing.

Attribute table before save:

|  FeatureIdentifier  | name | people |     geometry     |
----------------------------------------------------------
| jahan_0             | ali  | 23     | POINT(67.0 35.0) |
| jahan_1             | gh   | 245    | POINT(67.2 34.4) |
 ---------------------------------------------------------

Attribute table after reading shapefile:

|  FeatureIdentifier  | the_geom | name | people |
--------------------------------------------------
| mesal_0             |          | ali  | 23     |
| mesal_1             |          | gh   | 245    | 
 -------------------------------------------------

How can I save my feature collection into shapefile without loosing geometries? The problem is on storing. I tested the saved shp file by QGIS and saw geometries lost.

---

more code on saving shapefile:

DataStore dataStore = ...; // shapefile data store
// My FeatureCollection containing two features
SimpleFeatureCollection collection = ...; 
dataStore.createSchema(schema);
String typeName = dataStore.getTypeNames()[0];
SimpleFeatureSource fs = dataStore.getFeatureSource(typeName);
MyUtil.saveToFeatureStore(collection,(FeatureStore) fs);

MyUtil.java:

public class MyUtil{
  public static void saveToFeatureStore(SimpleFeatureCollection collection, FeatureStore featureStore){
    Transaction tx = new DefaultTransaction("create");
    featureStore.setTransaction(tx);
    try{
      featureStore.addFeatures(collection);
      tx.commit();
    } catch(Exception ex){
      tx.rollback();
    } finally{
      tx.close();
    }
  }
}

My problem is: How to save features into shapefile by GeoTools. There is no question about storing features by GeoTools at this site.

Answer 1

As you surmise you need to change the schema. As schema are immutable you need to copy the existing schema into a new one changing the name of the geometry attribute.

You will need something like:

public boolean writeFeatures(
        FeatureCollection<SimpleFeatureType, SimpleFeature> features) {

    if (shpDataStore == null) {
        throw new IllegalStateException(
                "Datastore can not be null when writing");
    }
    SimpleFeatureType schema = features.getSchema();
    GeometryDescriptor geom = schema
            .getGeometryDescriptor();

    try {

        /*
         * Write the features to the shapefile
         */
        Transaction transaction = new DefaultTransaction(
                "create");

        String typeName = shpDataStore.getTypeNames()[0];
        SimpleFeatureSource featureSource = shpDataStore
                .getFeatureSource(typeName);

        /*
         * The Shapefile format has a couple limitations: - "the_geom" is always
         * first, and used for the geometry attribute name - "the_geom" must be of
         * type Point, MultiPoint, MuiltiLineString, MultiPolygon - Attribute
         * names are limited in length - Not all data types are supported (example
         * Timestamp represented as Date)
         *
         * Because of this we have to rename the geometry element and then rebuild
         * the features to make sure that it is the first attribute.
         */

        List<AttributeDescriptor> attributes = schema
                .getAttributeDescriptors();
        GeometryType geomType = null;
        List<AttributeDescriptor> attribs = new ArrayList<AttributeDescriptor>();
        for (AttributeDescriptor attrib : attributes) {
            AttributeType type = attrib.getType();
            if (type instanceof GeometryType) {
                geomType = (GeometryType) type;

            } else {
                attribs.add(attrib);
            }
        }

        GeometryTypeImpl gt = new GeometryTypeImpl(
                new NameImpl("the_geom"), geomType.getBinding(),
                geomType.getCoordinateReferenceSystem(),
                geomType.isIdentified(), geomType.isAbstract(),
                geomType.getRestrictions(), geomType.getSuper(),
                geomType.getDescription());

        GeometryDescriptor geomDesc = new GeometryDescriptorImpl(
                gt, new NameImpl("the_geom"),
                geom.getMinOccurs(), geom.getMaxOccurs(),
                geom.isNillable(), geom.getDefaultValue());

        attribs.add(0, geomDesc);

        SimpleFeatureType shpType = new SimpleFeatureTypeImpl(
                schema.getName(), attribs, geomDesc,
                schema.isAbstract(), schema.getRestrictions(),
                schema.getSuper(), schema.getDescription());


        shpDataStore.createSchema(shpType);

        if (featureSource instanceof SimpleFeatureStore) {
            SimpleFeatureStore featureStore = (SimpleFeatureStore) featureSource;

            List<SimpleFeature> feats = new ArrayList<SimpleFeature>();

            FeatureIterator<SimpleFeature> features2 = features
                    .features();
            while (features2.hasNext()) {
                SimpleFeature f = features2.next();
                SimpleFeature reType = SimpleFeatureBuilder
                        .build(shpType, f.getAttributes(), "");

                feats.add(reType);
            }
            features2.close();
            SimpleFeatureCollection collection = new ListFeatureCollection(
                    shpType, feats);

            featureStore.setTransaction(transaction);
            try {
                List<FeatureId> ids = featureStore
                        .addFeatures(collection);
                transaction.commit();
            } catch (Exception problem) {
                problem.printStackTrace();
                transaction.rollback();
            } finally {
                transaction.close();
            }
            shpDataStore.dispose();
            return true;
        } else {
            shpDataStore.dispose();
            System.err.println("ShapefileStore not writable");
            return false;
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
    return false;
}

There is a full working example at https://github.com/ianturton/geotools-cookbook/tree/master/modules/output/src/main/java/org/ianturton/cookbook/output (including the pom file to sort out the dependencies)