Warning you are getting that 6781972fa25a3e577395c444 is not valid UUID is correct its should look something like this e58ed763-928c-4155-bee9-fdbaaadc15f3, you can read more here https://www.baeldung.com/java-uuid

_id : ObjectId(6781972fa25a3e577395c444)

this is object identifier used by mongo which kind of suggests that uuid is not being mapped to your _id field,

May you share complete code for better understanding ?