How do I iterate through entries in MongoDB 3.0? - mongodb

Question

We are trying to retrieve entries from the database (MongoDB) and place them in a db. When using DBCursor, we use cursor.hasNext() to get the next reading.
DBCursor is depreciated in MongoDB 2.0 and it is recommended to use FindIterable for MongoDB 3.0.
However when we use FindIterable, there isn't a similar hasNext() method.
How do I change my code below for 3.0?
BasicDBObject query = new BasicDBObject("timeStamp",
new BasicDBObject("$gte",from).append("$lt",to ));
DBCursor cursor = (DBCursor) newColl.find(query);
//FindIterable cursor = newColl.find(query);
while (cursor.hasNext()) {
DBObject latestEntry = cursor.next();
String json = latestEntry.toString();
Reading reading = gson.fromJson(json, Reading.class);
readingList.add(reading);
}
return readingList;

Answer 1

You can try something like below.
Document query = new Document("timeStamp",
new Document("$gte",from).append("$lt",to));
FindIterable<Document> find = newColl.find(query);
for (Document latestEntry : find) {
String json = latestEntry.toJson();
Reading reading = gson.fromJson(json, Reading.class);
readingList.add(reading);
}
return readingList;
Using Cursor
MongoCursor<Document> cursor = newColl.find(query).iterator();
while (cursor.hasNext()) {
Document latestEntry = cursor.next();
String json = latestEntry.toJson();
Reading reading = gson.fromJson(json, Reading.class);
readingList.add(reading);
}
return readingList;
Using Lambda
List<Reading> readingList= newColl.find().map(item -> gson.fromJson(item.toJson(), Reading.class)).into(new ArrayList<>());