24. GeoMesa Native API

The GeoMesa Native API (geomesa-native-api in the source distribution) is for developers who prefer not to use GeoTools interfaces and just want to geo index their data. It exposes a simple interface for persisting and querying GeoMesa as well as a simple integration point with Geoserver in cases where OGC access is still desired.

24.1. Usage

To interact with the GeoMesa Native API, instantiate an instance of a GeoMesaIndex<T> with your payload type T.

GeoMesaIndex<DomainObject> index =
                AccumuloGeoMesaIndex.build(
                    "hello",
                    "zoo1:2181",
                    "mycloud",
                    "myuser", "mypass",
                    true,
                    new DomainObjectValueSerializer(),
                    new DefaultSimpleFeatureView<DomainObject>("foo"));

In the code snippet above, we are instantiating an AccumuloGeoMesaIndex with a type parameter of DomainObject, the payload object type that is specific to each usage of the native API. We have provided a DomainObjectValueSerializer an implementation of ValueSerializer which tells the native API how to convert the domain object into a byte array payload. We have also provided a DefaultSimpleFeatureView which maintains integration with the Geotools infrastructure. The DefaultSimpleFeatureView will create a SimpleFeatureType that contains the geometry, date, and identifier of the DomainObject and enable querying based on these attributes. If you want to enable querying on more attributes from your domain object, you should create a class that extends SimpleFeatureView and converts the domain object into a rich SimpleFeature. You can then leverage GeoMesa’s secondary indexing optimizations on first class attributes.

Persisting data to a GeoMesaIndex requires utilizing the various insert methods. The following code snippet demonstrates how you can put domain objects into the index.

final GeometryFactory gf = JTSFactoryFinder.getGeometryFactory();
DomainObject one = new DomainObject();
DomainObject two = new DomainObject();
index.insert(
    one,
    gf.createPoint(new Coordinate(-78.0, 38.0)),
    date("2016-01-01T12:15:00.000Z"));
index.insert(
    two,
    gf.createPoint(new Coordinate(-78.0, 40.0)),
    date("2016-02-01T12:15:00.000Z"));

The code above will compute an identifier for each of the domain objects. If you want to control the identifiers, use the insert methods with id in the signature. If you do not intend to query GeoMesa using the specific identifiers of your domain object, prefer the method that generates an identifier for you. The reason is that the identifier chosen by GeoMesa optimizes the locality properties of the identifier and thus the caching within the underlying database.

To query data stored using the GeoMesa Native API, build up a GeoMesaQuery and pass it to the GeoMesaIndex.

For example, the following code snippet queries GeoMesa on space and time.

GeoMesaQuery q =
    GeoMesaQuery.GeoMesaQueryBuilder.builder()
        .within(-79.0, 37.0, -77.0, 39.0)
        .during(date("2016-01-01T00:00:00.000Z"), date("2016-03-01T00:00:00.000Z"))
        .build();
Iterable<DomainObject> results = index.query(q);

If you have used a custom SimpleFeatureView, you can query on the attributes you’ve lifted into the SimpleFeatureType. For instance, if you have lifted an attribute called age into the SimpleFeatureType, you can query on it as follows and GeoMesa will push the age predicate down for processing in the database.

FilterFactory ff = CommonFactoryFinder.getFilterFactory2();
GeoMesaQuery q =
    GeoMesaQuery.GeoMesaQueryBuilder.builder()
        .within(-79.0, 37.0, -77.0, 39.0)
        .during(date("2016-01-01T00:00:00.000Z"), date("2016-03-01T00:00:00.000Z"))
        .filter(ff.greaterThan(ff.property("age"), 30)
        .build();
Iterable<DomainObject> results = index.query(q);