Mongodb Java - How to return all fields of a collection

Question

With the driver Java Mongodb, I am looking for a way to return all fields of one collection.For example, I have a collection "people", how can I get all fields, I want output： 'id','name','city'...

Possible duplicate of [Query fields in a MongoDB Collection.](http://stackoverflow.com/questions/9639260/query-fields-in-a-mongodb-collection) — vijayst, Aug 23 '16 at 03:21
http://stackoverflow.com/questions/2298870/mongodb-get-names-of-all-keys-in-collection — Breavyn, Aug 23 '16 at 05:07
Thanks a lot, but I am trying to query all field name of a collection instead of specific fields. — C. Song, Aug 23 '16 at 10:13

score 3 · Answer 1 · edited Dec 08 '20 at 09:56

3

Thanks a lot, I have finally got the answer.

DBCursor cur = db.getCollection("people").find();
DBObject dbo = cur.next();
Set<String> s = dbo.keySet();

edited Dec 08 '20 at 09:56

menuka

61
8

answered Aug 23 '16 at 10:42

C. Song

41
1
3

score 1 · Answer 2 · answered Aug 23 '16 at 04:55

From manual:

To return all documents in a collection, call the find method without a criteria document. For example, the following operation queries for all documents in the restaurants collection.

FindIterable<Document> iterable = db.getCollection("restaurants").find();

Iterate the results and apply a block to each resulting document.

 iterable.forEach(new Block<Document>() {
        @Override
        public void apply(final Document document) {
            System.out.println(document);
        }
   });

score 0 · Answer 3 · answered Mar 28 '19 at 14:08

You'd need to decide on the number of samples that would make sense to you but this would pull the last 10 submissions.

Document nat = new Document().append("$natural",-1);
    FindIterable<Document> theLastDocumentSubmitted = collection.find().limit(10).sort(nat);

    ArrayList<String>fieldkeys = new ArrayList<String>();

    for (Document doc : theLastDocumentSubmitted) {
        Set<String> keys = doc.keySet();
        Iterator iterator = keys.iterator();
        while(iterator.hasNext()){
            String key = (String) iterator.next();
            String value = (String) doc.get(key).toString();
            if(!fieldkeys.contains(key)) {
                fieldkeys.add(key);
            }
        }
    }
    System.out.println("fieldkeys" + fieldkeys.toString());

score 0 · Answer 4 · answered Nov 11 '20 at 10:07

Below code will return all fields from given collection.

 MongoCollection<Document> mongoCollection = mongoDatabase.getCollection("collection_name");
                    AggregateIterable<Document> output = mongoCollection.aggregate(Arrays.asList(
                            new Document("$project", Document("arrayofkeyvalue", new Document("$objectToArray", "$$ROOT"))),
                            new Document("$unwind", "$arrayofkeyvalue"),
                            new Document("$group", new Document("_id", null).append("allkeys", new Document("$addToSet", "$arrayofkeyvalue.k")))
                    ));

score -1 · Answer 5 · answered Aug 23 '16 at 04:59

-1

Below code will return all fields of people collection :

db.people.find()

answered Aug 23 '16 at 04:59

S Kumar

1

This line returns a DBCursor object, then what should I do next? Use a method in DBCursor class? – C. Song Aug 23 '16 at 10:24

Mongodb Java - How to return all fields of a collection

5 Answers5