how to store array in mongodb?

Question

I want to store a simple array of latitude,longitude inside a mongoDB collection using java and I am using following code but my "loc" array always is empty :

BasicDBObject doc = new BasicDBObject();
//doc.put("key " , r.getKey());
doc.put("category" , r.getKey());
doc.put("type" , r.getValue());

BasicDBObject latlon = new BasicDBObject();


ArrayList<Float> aLatLong = new ArrayList<Float>();

{




    Float fLat = Float.parseFloat(r.getLatitude());
    Float fLon = Float.parseFloat(r.getLongitude());
    aLatLong.add(fLat);
    aLatLong.add(fLon);

    latlon.put("lat" , fLat);
    latlon.put("lon" , fLon);
}


doc.put( "loc" , aLatLong);

but when I don't use ArrayList at all and try to store latlon into "loc" it will show me the data but its not an array anymore.

how can I save a simple array in mongoDB?

Abhishek bhutra · Accepted Answer · 2012-07-30 12:59:54Z

2

Try this

BasicDBObject doc = new BasicDBObject();
//doc.put("key " , r.getKey());
doc.put("category" , r.getKey());
doc.put("type" , r.getValue());

java.util.Map<String,Float> latLongMap = new java.util.HashMap<String,Float>();
latLongMap.put("lat" , Float.parseFloat(r.getLatitude());
latLongMap.put("lon" , Float.parseFloat(r.getLongitude());

doc.put( "location" , latLongMap);

This will store a json of lat-long. Also if you want to store them as array, that is also possible but i will suggest you store them as this.

answered Jul 30, 2012 at 12:59

Abhishek bhutra

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Abhishek bhutra · Accepted Answer · 2012-07-30 13:12:35Z

1

All you need to do is this :

BasicDBObject doc = new BasicDBObject();

doc.put("category" , r.getKey());
doc.put("type" , r.getValue());

List<Float> aLatLong = new ArrayList<Float>();

Float fLat = Float.parseFloat(r.getLatitude());
Float fLon = Float.parseFloat(r.getLongitude());
aLatLong.add(fLat);
aLatLong.add(fLon);

doc.put( "loc" , aLatLong);

now use the insert method of mongodb to save the DBObject.

edited Jul 30, 2012 at 13:12

Abhishek bhutra

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answered Jul 30, 2012 at 12:46

Byter

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4 Comments

Byter Over a year ago

BasicDBObject internally knows how to serialize any instance of Iterable.(Thus the List gets properly serialized and stored in mongo)

Vahid Hashemi Over a year ago

I am doing the very same in my above example!!! and also I copy your snippet into my code and it doesn't work

Byter Over a year ago

so is the array empty in mongo database after u tried the code?

Byter Over a year ago

hey it is working for me... can u please post the output JSON of the find() method.

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