How to get distance - MongoDB Template Near function - spring

Question

I'm trying to find Near by places.
Below code is working fine.
But i'm not able to get actual distance of place from my given lat,lng.
Criteria criteria = new Criteria("coordinates")
.near(new Point(searchRequest.getLat(),searchRequest.getLng()));
Query query = new Query();
query.addCriteria(criteria);
query.addCriteria(criteriaName);
query.limit(5);
List<Place> ls = (List<Place>) mongoTemplate.find(query, Place.class);

Answer 1

You can do it with geoNear aggregation. In spring-data-mongodb GeoNearOperation is representing this aggregation.
Extend or create inherit Place class with field where you would like to have distance information (example with inheritance):
public class PlaceWithDistance extends Place {
private double distance;
public double getDistance() {
return distance;
}
public void setDistance(final double distance) {
this.distance = distance;
}
}
Instead of Criteria with Query use aggregation. Second argument of geoNear is name of field where distance should be set:
final NearQuery nearQuery = NearQuery
.near(new Point(searchRequest.getLat(), searchRequest.getLng()));
nearQuery.num(5);
nearQuery.spherical(true); // if using 2dsphere index, otherwise delete or set false
// "distance" argument is name of field for distance
final Aggregation a = newAggregation(geoNear(nearQuery, "distance"));
final AggregationResults<PlaceWithDistance> results =
mongoTemplate.aggregate(a, Place.class, PlaceWithDistance.class);
// results.forEach(System.out::println);
List<PlaceWithDistance> ls = results.getMappedResults();
Just to make it easier - associated imports:
import static org.springframework.data.mongodb.core.aggregation.Aggregation.geoNear;
import static org.springframework.data.mongodb.core.aggregation.Aggregation.newAggregation;
import org.springframework.data.mongodb.core.aggregation.Aggregation;
import org.springframework.data.mongodb.core.aggregation.AggregationResults;
import org.springframework.data.mongodb.core.aggregation.GeoNearOperation;
import org.springframework.data.mongodb.core.query.NearQuery;

Answer 2

Walery Strauch's example was useful for me...
However I wanted to :
run aggregate query to get all the points in 2dsphere index with-in given distance in Kilometers or Meters. You can use Metrics.KILOMETERS & Metrics.MILES
collection name is not specified as part of pojo
I have 2dsphere index with old way of representation in MongoDB. I am using Mongo as sharded databased for Geo-Spatial queries. My nearSphere query (without aggregation) was failing only when there is a shard key added into the same collection where I have 2dsphere index.
After using below implementation with shard key in the same collection. I am successfully able to fetch the required data.
Here is the sample :
import org.springframework.data.geo.Metrics;
final NearQuery query = NearQuery.near(new Point(longitude, latitude), Metrics.KILOMETERS)
.num(limit)
.minDistance(distanceInKiloMeters)
.maxDistance(maxNearByUEDistanceInKiloMeters)
.spherical(true);
final Aggregation a = newAggregation(geoNear(query, "distance"));
final AggregationResults<PlaceWithDistance> results = offlineMongoTemplate.aggregate(a, "myCollectionName", PlaceWithDistance.class);
final List<PlaceWithDistance> measurements = new ArrayList<PlaceWithDistance>(results.getMappedResults());