Extracting fields from JSON fields from mongodb

Question

I want to extract all these places mentioned in "location" field and does not want the other fields in the below json.but can't be able to extract since it is nested..Can anyone help me?

    DBCursor cursorTotal = coll.find(obje);

    while (cursorTotal.hasNext()) {

        DBObject curNext = cursorTotal.next();

        System.out.println("data::"+curNext.get("list.myList.location");
   }

My "curNext" gives output as::

    {
    "_id": {
    "$oid": "51ebe983e4b0d529b4df2a0e"
    },
    "date": {
    "$date": "2013-07-21T13:31:11.000Z"
    },
    "lTitle": "Three held for running CISF job racket",
    "list": {
    "myList": [
        {
            "location": "Germany"
        },
        {
            "location": "Geneva"
        },
        {
            "location": "Paris"
        }
    ]
    },
    "hash": -1535814113,
    "category": "news"
}

I want my output as

Germany,Geneva,Paris

@BetaRide i have updated my question and added one of my trial — sooraj g
– sooraj g, Commented Apr 7, 2015 at 7:19

sooraj g · Accepted Answer · 2015-04-09 05:25:17Z

2

I have been in a long wait here for an answer and finally I got what I was searching for...Just noting my answer so someone else can benefit from it

  DBCursor cursorTotal = coll.find(obje);

    while (cursorTotal.hasNext()) {

    DBObject curNext = cursorTotal.next();

            String res=curNext.toString();
           JsonElement jelement = new JsonParser().parse(res);
            JsonObject  jobject = jelement.getAsJsonObject();
            jobject = jobject.getAsJsonObject("list");
            JsonArray jarray = jobject.getAsJsonArray("myList");
            jobject = jarray.get(0).getAsJsonObject();
            String result = jobject.get("location").getAsString();


            System.out.println("all places::"+result);
}

edited Apr 9, 2015 at 5:25

answered Apr 7, 2015 at 8:19

sooraj g

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Comments

Neo-coder · Accepted Answer · 2015-04-07 07:25:55Z

0

For finding only locations you should used mongo aggregation, below query will fetch all lcoations array

    db.collectionName.aggregate({
    "$unwind": "$ner.nerList"
},
{
    "$group": {
    "_id": "$_id",
    "location": {
        "$push": "$ner.nerList.location"
    }
    }
},
{
    "$project": {
    "location": "$location",
    "_id": 0
    }
})

Unfortunately I don't know how to convert this in Java but, I find below links which helpfull to you for converting above query in java format Mongo Java aggregation driver

answered Apr 7, 2015 at 7:25

Neo-coder

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