Convert dbcursor object into json

Question

I have a java application where I want to send json data fro servlet to a jsp. I am using mongodb as a database and Gson library for Json.

I am new to Java & Mongo.

Here is the code for querying the database:

MongoClient mongoClient = new MongoClient("localhost", 27017);
DB database = mongoClient.getDB("MyTestDatabase");
coll = database.getCollection("players");

BasicDBObject fields = new BasicDBObject();

    fields.put("_id", 0);
    fields.put("Incident Date", 1);
    fields.put("Longitude", 1);
    fields.put("Latitude", 1);
    fields.put("Address", 1);
    fields.put("Status", 1);
    fields.put("Name", 1);

    doc.put("Address", "Mumbai");

    cursor = coll.find(doc,fields);

And this is the result after querying the database

{ "_id" : { "$oid" : "5540cae37a104f6bbfe7c9f5"} , "Incident Date" : "30/4/2015" , "Longitude" : "77.61528809" , "Latitude" : "12.9245331" , "Address" : "Mumbai" , "Status" : "Ok" , "Name" : [ "1.ABC" , "2.XYZ" , "3.PQR"]}

What I want to achieve is to convert the above result into a JSON and access the JSON using fields such as 'Incident Date', 'Status' by parsing the result as json. I tried to parse the original result as json but I think it doesn't work like that

Here is what I have tried. 1. Converted the 'cursor' to ArrayList

    List<DBObject> myList = new ArrayList<DBObject>();
    myList = cursor.toArray();

2. Tried to convert the ArrayList into the JSON

   JSON json =new JSON();
   String serialize = json.serialize(cursor);
   

I tried the following code, but I am getting this error

    JsonElement jelement = new JsonParser().parse(serialize);
    System.out.println(jelement);
    JsonObject  jobject = jelement.getAsJsonObject();//error at this line
    System.out.println(jobject);

Exception in thread "main" java.lang.IllegalStateException: Not a JSON Object: [{"_id":{"$oid":"5540cae37a104f6bbfe7c9f5"},"Incident Date":"30/4/2015","Longitude":"77.61528809","Latitude":"12.9245331","Address":"Mumbai","Status":"Ok","Culprits Name":["1.ABC","2.XYZ","3.PQR"]}]
at com.google.gson.JsonElement.getAsJsonObject(JsonElement.java:90)

Can anyone please help me?

Answer 1

Iterate over cursor and push data into JSONObject and then put jsonObject into jsonarray like this :

public JSONArray getJsonData() throws JSONException {
  JSONArray jsonarray = new JSONArray();
  BasicDBObject criteria = new BasicDBObject();
  BasicDBObject projections = new BasicDBObject();
  criteria.put("Address", "Mumbai");
  projections.put("_id", 0);
  projections.put("Incident Date", 1);
  projections.put("Longitude", 1);
  projections.put("Latitude", 1);
  projections.put("Address", 1);
  projections.put("Status", 1);
  projections.put("Name", 1);
  DBCursor cursor = coll.find(criteria, projections);
  while(cursor.hasNext()) {
    BasicDBObject obj = (BasicDBObject) cursor.next();
    jsonobj = new JSONObject();
    BasicDBList name = (BasicDBList) obj.get("Name");
    jsonobj.put("Incident Date", obj.getString("Incident Date"));
    jsonobj.put("Longitude", obj.getString("Longitude"));
    jsonobj.put("Latitude", obj.getString("Latitude"));
    jsonobj.put("Address", obj.getString("Address"));
    jsonobj.put("Status", obj.getString("Status"));
    jsonobj.put("Name", name);
    jsonarray.put(jsonobj);
  }
  return jsonarray;
}