Calculate distance in Java Using MongoDB

Question

I am working on location calculation in Java and MongoDB. I pass latitude and longitude to method and find nearest location from provided input. I am able to get Location name from my master table where i have all landmarks with latitude and longitude.

My requirement is that i want to get location with distance using MongoDB - like 4Km from XYZ . MongoDB has Geospatial query and i am working on it. I can get mentioned input by running in command prompt by using db.runCommand({ geoNear : "data", near : [-73.9000, 40.7000], spherical : true, maxDistance : 2500/6378137, distanceMultiplier: 6378137}).

I am looking equivalent code in Java, so i can pass latitude and longitude only and get nearest location with distance.

Thanks in advance.

Answer 1

You can perform the command with the "command" method of the DB object in the Java Driver. The API documentation may be found here: http://api.mongodb.org/java/current/com/mongodb/DB.html#command%28com.mongodb.DBObject%29

Here is how the command may be performed using the Java driver:

BasicDBObject myCmd = new BasicDBObject();
myCmd.append("geoNear", "data");
double[] loc = {-73.9000, 40.7000};
myCmd.append("near", loc);
myCmd.append("spherical", true);
myCmd.append("maxDistance", (double)2500/6378137);
myCmd.append("distanceMultiplier", 6378137);
System.out.println(myCmd);
CommandResult myResult = db.command(myCmd);
System.out.println(myResult.toString());

I added some System.out.println statements, so you can see what the command document looks like, and a string representation of the results that are returned.
You can add num : 1 to the command document to limit the results to 1.

myCmd.append("num", 1);

This is noted in the geoNear documentation: http://www.mongodb.org/display/DOCS/Geospatial+Indexing#GeospatialIndexing-geoNearCommand

Hopefully this will get you started. Good luck!

Answer 2

There is a Java API available that let's you interact with it. The driver has a "command" method that does what you want.

Be sure to read the posted tutorial on the Java driver and how to translate shell commands into Java.