find in MongoCollection

Question

I have a MongoCollection in which I assign a collection. I\'m trying to find a user by his id.

user = (Document) usersCollection         


        

Answer 1

Your issue is that you assume that the find() method returns a single Document. It doesn't. It returns a list of them.

In MongoDB 2 Java driver there was a method on the DBCollection class named findOne(). In the MongoDB 3 Java driver API, the findOne() method isn't there. So your new code for finding exactly one document becomes similar too this one:

collection.find(eq("_id", 3)).first()

where eq("_id", 3) is called a filter on your collection.