mongoDB查询某个经纬度附近的用户

需求：获取某个点100m内的用户

数据库：mongoDB

语言：JAVA

1.地理位置数据以GeoJSON 的格式存储的

loc : {
type : "Point",
coordinates : [lng, lat]
}

查询地理位置用到geoWithin，可以查询多边形的地理位置信息，地球接近圆形，这里用到centerSphere， 查询语句为

{
location field: {
$geoWithin: { $centerSphere: [ [ x, y ], radius] }
}
}

x,y为中心点的经纬度，radius为距离中心点的距离，$centerSphere 使用弧度(radians)作为距离

距离与弧度之间的转换：

distance to radians: divide the distance by the radius of the sphere (e.g. the Earth) in the same units as the distance measurement.

radians to distance: multiply the radian measure by the radius of the sphere (e.g. the Earth) in the units system that you want to convert the distance to.

地球赤道的半径为3963.2 miles， 即 6378.1 kilometers， 只查找100m范围内，则radius为100/6378100。

参考信息：

geowithin

centerSphere

calculate distances

Coordinates中数据类似如下：

{
"_id" : ObjectId("58403433785509513efe3279"),
"account" : "18520222222",
"platform" : "android",
"location" : {
"type" : "Point",
"coordinates" : [
108.840974298098,
34.2789316522934
]
},
"collectTime" : 1480602671,
"logTime" : 1480602675
}

JAVA代码，此处只写了unit test, 简单测试代码逻辑。实际使用需要做相应改动。

package mongo;

import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;

import org.bson.Document;
import org.junit.Before;
import org.junit.Test;

import com.mongodb.BasicDBList;
import com.mongodb.BasicDBObject;
import com.mongodb.MongoClient;
import com.mongodb.MongoClientOptions;
import com.mongodb.MongoCredential;
import com.mongodb.MongoException;
import com.mongodb.ServerAddress;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.MongoDatabase;

public class CoordinatesTest {

public static final String mgoHost = "127.0.0.1:27017";
public static final String mgoUser = "test";
public static final String mgoPwd = "123456";
public static final String mgoDB = "info";

private static MongoDatabase db = null;

@SuppressWarnings("resource")
public void initMongo() throws UnknownHostException, MongoException {
MongoClientOptions.Builder build = new MongoClientOptions.Builder();
build.connectionsPerHost(50);
build.threadsAllowedToBlockForConnectionMultiplier(50);
build.maxWaitTime(1000*60*2);
build.connectTimeout(1000*30);
build.socketTimeout(1000*30);

List<ServerAddress> seeds = new ArrayList<ServerAddress>();
seeds.add(new ServerAddress(mgoHost));
MongoCredential credentials = MongoCredential.createScramSha1Credential(mgoUser, mgoDB, mgoPwd.toCharArray());
List<MongoCredential> credentialsList = new ArrayList<MongoCredential>();
credentialsList.add(credentials);
MongoClient mongoClient = new MongoClient(seeds, credentialsList, build.build());
db = mongoClient.getDatabase(mgoDB);
}

public static List<String> distinct(String coll, BasicDBObject query, String key) {
List<String> list = new ArrayList<String>();
MongoCursor<Document> cursor = null;
try {
cursor = db.getCollection(coll).find(query).projection(new BasicDBObject(key, 1)).iterator();
if (cursor != null) {
HashSet<String> set = new HashSet<String>();
while (cursor.hasNext()){
Document doc = cursor.next();
String val = doc.getString(key);
if (!set.contains(val)) {
set.add(val);
}
}
list.addAll(set);
}
} catch (Throwable e) {
System.err.println("coll:"+coll+", query:"+query+", key:"+key+", occur exception: " + e.getMessage());
} finally {
if (cursor != null) {
cursor.close();
}
}
return list;
}

public static List<String> getAccountsByLocation(double longitude, double latitude, double radius) {
BasicDBList point = new BasicDBList();
point.add(longitude);
point.add(latitude);
Double distance = radius/6378100;
BasicDBList centerSphere = new BasicDBList();
centerSphere.add(point);
centerSphere.add(distance);
BasicDBObject location = new BasicDBObject("$geoWithin", new BasicDBObject("$centerSphere", centerSphere));
BasicDBObject query = new BasicDBObject("location", location);

List<String> list = new ArrayList<String>();
try {
list = CoordinatesTest.distinct("Coordinates", query, "account");
} catch (MongoException e) {
System.err.println(e.getMessage());
}
return list;
}

@Before
public void init() throws Exception {
initMongo();
}

@Test
public void test1() {
List<String> accountList = getAccountsByLocation(113.941892, 22.50986, 100);
System.out.println(accountList);
}
}