How to retrieve a single field from MongoDB in Java

Question

I am trying to retrieve a field from a document and set it equal to a variable so when I update it later I can just do (field + newCount) or something like that.

For

Answer 1

Here is how you'd retrieve a single field from MongoDB, driver version 3.0.2 You create a query with a projection:

    Document document = collection
            .find(new BasicDBObject("username", "testusername"))
             .projection(Projections.fields(Projections.include("price"), Projections.excludeId())).first();

Then, you can extract this field as double with the following code:

    double price = document.getDouble("price");