*/
public <T extends Object> T save(T obj) {
MongoEntity moe = Mongos.entity(obj);
String collName = moe.getCollectionName(obj);
if (db.collectionExists(collName)) {
moe.fillIdIfNoexits(obj);
DBObject dbo = moe.toDBObject(obj);
DBCollection coll = db.getCollection(collName);
coll.save(dbo);
return obj;
}