Hibernate Spatial - Query within an X kilometer radius?

Question

I am new to Hibernate Spatial, and am trying to perform a simple query of objects within a given radius. I've created a number of entries in my database with properties corresponding to a latitude and longitude, using data from Google Maps and other sources. This property is defined like this in my Entity class:

@Column
@Type(type = "org.hibernate.spatial.GeometryType")
private Point coordinates = null;

I'm now trying to figure out how to do a search of all entity objects that have coordinates that fall within a radius of x kilometers from a given point. For example, I'd like to find objects that fall within a 50 kilometer radius of the point (12.34567, -76.54321). However, I can't find any examples or tutorials that would explain how to do this in Hibernate Spatial.

Can anyone give me any information on how a query like this can be constructed?

score 16 · Accepted Answer · edited Aug 24 '15 at 10:04

16

See ~~this resource~~ for a tutorial with "Spatial Queries", which a special dialect and the JTS library (Open Source).

Basically you do the following (copy/paste from the referenced page):

import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.geom.Point;
import com.vividsolutions.jts.io.ParseException;
import com.vividsolutions.jts.io.WKTReader;
import util.JPAUtil;

import javax.persistence.EntityManager;
import javax.persistence.Query;
import java.util.Date;
import java.util.List;

.......

private List find(String wktFilter) {
    Geometry filter = wktToGeometry(wktFilter);
    EntityManager em = JPAUtil.createEntityManager();
    em.getTransaction().begin();
    Query query = em.createQuery("select e from Event e where within(e.location, :filter) = true", Event.class);
    query.setParameter("filter", filter);
    return query.getResultList();
}

private Geometry wktToGeometry(String wktPoint) {
    WKTReader fromText = new WKTReader();
    Geometry geom = null;
    try {
        geom = fromText.read(wktPoint);
    } catch (ParseException e) {
        throw new RuntimeException("Not a WKT string:" + wktPoint);
    }
    return geom;
}

For generating a circle, see this resource (search for "Arcs, Circles and Curves"). Again a copy/paste from there:

//this method replaces the above wktToGeometry() method
private static Geometry createCircle(double x, double y, final double RADIUS) {
  GeometricShapeFactory shapeFactory = new GeometricShapeFactory();
  shapeFactory.setNumPoints(32);
  shapeFactory.setCentre(new Coordinate(x, y));//there are your coordinates
  shapeFactory.setSize(RADIUS * 2);//this is how you set the radius
  return shapeFactory.createCircle();
}

Besides you always have the workaround, in which to add some additional fields ( mapped withinsertable=false, updatable=false) to map to the same columns used by the org.hibernate.spatial.GeometryType and then use them in your query. For computing the distance, check the euclidian distance formula.

edited Aug 24 '15 at 10:04

Mohammad Faisal

5,783
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answered Nov 21 '13 at 22:05

V G

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The example shown on that page shows querying a point within a given polygon. Do I have to specify a polygon in my query? Ideally I'd be able to give it a point (lat/long) and a radius and use that in my query instead of a polygon. How can I declare that Geometry using JTS/Hibernate Spatial? – Shadowman Nov 22 '13 at 01:55
Well, a circle is a special Geometry, but not a Polygon. See my updated example to see how you create a circle. – V G Nov 22 '13 at 08:58
Okay, that all makes sense. I'll give it a shot. Unfortunately, though, I'm running into this error (http://stackoverflow.com/questions/20079825/hibernate-spatial-invalid-endian-flag-value-encountered-exception) which makes testing impossible until I get it resolved. – Shadowman Nov 22 '13 at 20:29
I have finally gotten past my error and began testing your answer. It all makes sense to me, but I think I'm having a problem setting the radius size. I want to query a particular latitude/longitude and get the objects within a 12 KM radius. How do I convert 12 KM to a unit of measure that the "shapeFactory.setSize()" line will properly interpret? My initial testing is indicating that I'm doing it wrong. – Shadowman Nov 29 '13 at 18:25
According to the referenced link you are doing it correctly. Try do debug the SQL queries with very little DB data in order to see if the queries are correct. – V G Nov 29 '13 at 19:06
Okay, I've done some detailed testing and it appears as though the shapeFactory.setSize(RADIUS * 2) line gives me inaccurate results. The radius ends up MUCH larger than I intended. After some trial and error, I found that I get somewhat more accurate results with shapeFactory.setSize((RADIUS * 2) / 100). I still find that it is still off by a considerable margin in some cases, however. Thoughts? – Shadowman Nov 30 '13 at 02:41
Thought: try changing the number of points... with `setNumPoints()` – V G Nov 30 '13 at 10:48
1

I nead the exact same thing...how can you determin that the radius is a unit of meter/kilometer and so on?? – simonC Jun 23 '14 at 13:22
@AndreiI Great solution but I still can'T see from your answer how I get a 50km search radius. Could you please add this to your answer? Thanks! – stephan1002 Jul 17 '15 at 21:37
@AndreiI I still don't get how do I set the radius in km? – Michael Jul 27 '15 at 23:13
@simonC Did you find any solution? – Michael Jul 27 '15 at 23:13
@confile Did you find the solution for the radius? – gabriel Nov 08 '16 at 10:08
1

This calculate the Euclidean distance, for the case of Earth coordinates, does not work – cdr89 Apr 25 '19 at 21:09

Hibernate Spatial - Query within an X kilometer radius?

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