public static String getRainfall(String date, String state)
  {
    DB db = _mongo.getDB(DATABASE_NAME);
    DBCollection coll = db.getCollection(COLLECTION_RAINFALL);
    
    BasicDBObject query = new BasicDBObject();
    query.put("year", "" + getYear(date));
    query.put("month", "" + getMonth(date));
    query.put("day", "" + getDay(date));
    query.put("state", "" + state);
    
    DBCursor cur = coll.find(query);

    DBObject doc = null;
    if (cur.hasNext()) {
      doc = cur.next();
      return getValue(doc, "rainfall");
    }
    
    return "";
  }