java - How to generate unique object id in mongodb

Question

When I use Mongodb with Java, I want to generate Object id at clients. Before I insert a record, however, I have to query mongodb first to make sure that the id generated by ObjectId() method is unique. Is there any way that I can generate unique object id without accessing mongodb twice?

Answer 1

You can generate ObjectId on the client without consulting database. Such ID will be unique (you'll have to try damn hard to get two identical object ids).

ObjectId id = new ObjectId();

// or this
ObjectId id = ObjectId.get();