bson/src/main/org/bson/LazyBSONCallback.java
public Object createDBRef(final String ns, final ObjectId id) {
        return new BasicBSONObject("$ns", ns).append("$id", id);
    }
public Object createDBRef(final String ns, final ObjectId id) {
        return new BasicBSONObject("$ns", ns).append("$id", id);
    }
This is a factory method pattern to create appropriate objects for BSON type DBPointer(0x0c).

@param ns the namespace of the reference
@param id the identifier of the reference
@return object to be used as reference representation