My advice would be to not misuse exceptions. They're there to cater for exceptional circumstances: a validation error during the login procedure is something that happens as a matter of course, it is not an exceptional state in my opinion.

If you do want to continue using exceptions in this nature, perhaps focus on capturing specific types of exceptions and have a more narrow focus on the code between the try and catch. Consider catching only LoginValidationException or some such before you fall back to a generic exception.