Extract Multiple Fields Using MongoDB 3.2.0 Java Driver

Question

Using the MongoDB 3.2.0 Java driver, which offers a Document object that seems different from a "BasicDBObject" or "DBObject", I would like to extract all the fields in a given document. For example, I have this document:

{ "sponsor" : "ABC Bicycles", "start" : "Herndon", "miles" : 50 }

I'd like to extract the values of "sponsor", "start", and "miles" using an Iterator. I've tried:

theSponsor = cursor.next().get("sponsor").toString();

which works fine for the "sponsor" field, but how can I pull the values of "start" and "miles" for this same question, using the same cursor? Perhaps I need something other than

MongoCursor<Document> cursor = collection.find().iterator();

How about storing the object? while (cursor.hasNext()) { Document doc = cursor.next(); theSponsor = doc.get("sponsor").toString(); theStart = doc.get("start").toString(); theMiles = doc.get("miles").toString();} ? — AndrewMcCoist
– AndrewMcCoist, Commented Jan 9, 2016 at 17:02

AndrewMcCoist · Accepted Answer · 2016-01-09 18:51:33Z

1

You can try the following:

String sponsor;
String start;
String miles;
Document doc;

while(cursor.hasNext()){
    doc = cursor.next();
    sponsor = doc.get("sponsor").toString();
    start = doc.get("start").toString();
    miles = doc.get("miles").toString();

    // Process your values and go to the next record 
}

You should check if your fields exist in the Document (as far as I remember, Mongo API used to throw some Exception in case it couldn't find the field). And of course, before calling toString() method, check if the objects aren't null to avoid NullPointerException. :)

edited Jan 9, 2016 at 18:51

answered Jan 9, 2016 at 17:08

AndrewMcCoist

6394 silver badges13 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Bob Cochran Over a year ago

Thank you very much! This works great! I really appreciate your help with this. I will try to figure out how to "accept" this answer.

AndrewMcCoist Over a year ago

I'm happy my advice was useful. It's just a common practice working with iterators / cursors ;)

Collectives™ on Stack Overflow

Extract Multiple Fields Using MongoDB 3.2.0 Java Driver

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related