How to Update a Value with MongoDB

Question

I want to add 1 point to a user each time he does something. So, I did this to create the user if not found and give him 1 point. I am stuck where I don't know how to update the value and add 1 point.

//Add One Point
   Document memberdoc = new Document("Username", event.getAuthor().getName());
   Document found = (Document) collection.find(memberdoc).first();
   if (found == null){
      memberdoc.append("Points", 1);
      memberdoc.append("UserID", event.getAuthor().getId());
      collection.insertOne(memberdoc);
      membersDataHashMap.put(event.getAuthor().getId(), new MembersData(event.getAuthor().getName(), event.getAuthor().getId(), 1));
    }else{
         String  id = found.getString("UserID");
         int points = found.getInteger("Points");
         membersDataHashMap.put(event.getAuthor().getId(), new MembersData(event.getAuthor().getId(),id,points + 1));
    }
//End

Answer 1

You need to use $inc operator with updateOne method of db.collection. For more details have a look official documentation of mongodb

In your case you can use it in the else condition as follows:

    //Add One Point
    Document memberdoc = new Document("Username", event.getAuthor().getName());
    Document found = (Document) collection.find(memberdoc).first();
    if (found == null){
        memberdoc.append("Points", 1);
        memberdoc.append("UserID", event.getAuthor().getId());
        collection.insertOne(memberdoc);
        membersDataHashMap.put(event.getAuthor().getId(), new MembersData(event.getAuthor().getName(), event.getAuthor().getId(), 1));
    }else{
        String  id = found.getString("UserID");
        int points = found.getInteger("Points");
        collection.updateOne(
            eq("UserID", found.getString("UserID")),
            new Document("$inc", new Document("Points", 1))
        );
        membersDataHashMap.put(event.getAuthor().getId(), new MembersData(event.getAuthor().getId(),id,points + 1));
    }
    //End

Focus on below part only:

collection.updateOne(
        eq("UserID", found.getString("UserID")),
        new Document("$inc", new Document("Points", 1))
    );

Which will find the matching user and increment the column Points by 1. Hope this will resolved your problem.