findOne implementation changed while upgrading to mongo-java-driver 3.3.0

Question

We were previously using mongo-java-driver 3.0.4 , where in a certain block of code has this implementation -

DBCollection docCollection = mongoClient.getDB(dbName).getCollection(collectionName);

Map<String, Object> docMap = doc.toMap(); // where doc is the CustomDocument

DBObject currentObj = docCollection.findOne(new QueryBuilder().put("id").is(doc.getId()).get());
if(currentObj == null) {
   docCollection.insert(new BasicDBObject(docMap));
} else {
   docCollection.update(currentObj, new BasicDBObject(docMap));
}

What I am trying to achieve now is use mongo-java-driver 3.3.0 and update the code to get rid of deprecated classes and methods. What I've tried corresponding to the above piece of code is -

MongoCollection<CustomDocument> docCollections = mongoClient.getDatabase(dbName).getCollection(collectionName, CustomDocument.class);

Bson filter = Filters.eq("id", doc.getId()); // where doc is the CustomDocument
FindIterable<Document> documentList = docCollections.find(filter);
if (documentList == null) {
    docCollections.insertOne(doc);
} else {
    docCollections.findOneAndUpdate(filter, new BasicDBObject(docMap));
}

What I still find missing is the findOne implementation from the collection in my code and the check based actions to be performed for insert and update accordingly.

Any solution/suggestion to this are welcomed.

Answer 1

I've found a solution playing around with the implementation in mongo-java-driver 3.3.0.

An easy way of performing findOne is now as follows -

MongoCollection<CustomDocument> docCollections = mongoClient.getDatabase(dbName).getCollection(collectionName, CustomDocument.class);
CustomDocument firstDocument = docCollections.find(filter).first(); //first for findOne