MongoDB Embedded object creation in Java without morphia.

First of all it's easier to ask one question per post ;)

Doing updates with the java driver is pretty straightforward, if a bit verbose :

Say your mongo update would look like :

db.users.friends({_id: <someuserid>}, {$push:{friends:{friend_id:...., friendname: ....}}})

All you have to do in Java is create a DBObject that encapsulates that update, so in this case :

DBObject query = new BasicDBObject("_id", <someuserid>);

DBObject newFriend = new BasicDBObject("friend_id", ...);
newFriend.put("friendname", ....);

DBObject update = new BasicDBObject("$push", new BasicDBObject("friends", newFriend));

DBCollection col = db.getCollection("users");

col.update(query, update);

Excuse any typoes, I haven't actually syntax checked this or anything but it should get you started. It's worth noting that it's important to be able to do these things in shell before trying it in Java. The API als has QueryBuilder which eases query object construction.

Full API documentation can be found here : http://api.mongodb.org/java/2.6.3/

Like Remon said, I think it's a good idea to go with an ORM as it usually presents a more production-ready approach than rolling your own. It sounds like you want to use object references to me. By using the @Reference annotation, I am able to "embed" objects within another object and then once I've loaded the owning object, I can get access to the owned object (I think this uses eager loading). An example:

@Entity public class PlaylistItem extends SomeModel{
   @Required
   @Reference
   public Playlist playlist;

   @Required
   @Reference
   public Track track;
}

Playlist and Track are two models annotated with @Entity, just like this PlaylistItem object.

Hope this helps.

More info on Morphia annotations here: http://code.google.com/p/morphia/wiki/AllAnnotations. There is even an Embeddd annotation but I have never had to use that.