Right not `ConstraintViolationException` have method getConstraintName() which can return the name of the SQL string. However, there's no general way to link this constraint name to the bean field(s) which the value breaks this constrain.

As this exception always have an `SQLException` as its cause, it should be possible to get more information from the error message of that exception.

For example for Postgres driver (`PSQLException`) the error may looks something like

```
ERROR: duplicate key value violates unique constraint "member_username_key"
Detail: Key (username)=(some-username-which-already-dup-in-system) already exists.
```

and currently getConstraintName() can return "member_username_key".

It should be possible to return the table column name `username`, or even better return the field `String username` in domain bean `Member`.