I guess you used UUID for user_id.
UUID is strange when working with JPA. We are mapping that out to varchar, so they're kind of meant to be a binary or String. You need the @Type annotation to tell JPA how you want to store them. If you save them as binary and work with the DB directly and do a select statement on it, you don't see the UUID
Adding this annotation will hopefully solve the problem

@Type(type="org.hibernate.type.UUIDCharType")