查询特定的Mongodb字段

Question

I need to have the following query converted in to Java code

use dbName
db.collectionName.find({},{reference:1})

I am trying to fetch the value for the key 'reference'

I tried the following but this doesn't seem to be the way

  Mongo dbConnection;
        DB dbobject;
        dbConnection = new Mongo("localhost", 27017);
        dbobject = dbConnection.getDB("dbName");
        DBCollection profileCollection = dbobject.getCollection("collectionName");
        BasicDBObject query = new BasicDBObject();
        query.put("{},{reference:1}");
        DBCursor mongocursor =profileCollection.find("{}, {reference:1}");
        try {
            while(mongocursor.hasNext()) {
               System.out.println(mongocursor.next().get("reference"));
            }
        } finally {
            mongocursor.close();
        }

Answer 1

Try the following

basicDBObject uqery = new BasicDBObject();
query.put("reference", 1);
DBCursor cursor = profilecollection.find(query);

you do not need to specify {} ... it is a default options for returning all the fields