the JDBC connection
String DRIVER = "com.mysql.jdbc.Driver";

converts the username: imtheuser1

into: intheuser1@myremotehostname.com

and then denies that user access to the database! How do I prevent JDBC elongating the username? Because it should work if it doesn't do that. (And I can't add the hostname to my login because I'm on a dynamic ip allocation, so it changes every time I restart my connection!)

consider asking this question in a JAVA forum, as its a JAVA issue not a MySQL issue
or consider GRANTing permissions to that user from any host

It's not a Java issue.

It's a mysql host-based authentication issue. It would be useful if it was possible to grant access on a domain name basis. I get the impression that mysql host access really means host.domain or anyhost.anydomain and that could clearly be improved upon.