'Error calling Driver#connect' is normally an error you get when Tomcat isn't able to reach you database. It may be because you provided the wrong username/password combination or because your database (or Amazon in that case) might be blocking the connection from the source IP.
I recommend you find the source IP and port from where you make the requests and add it to the user privileges in mysql. Grant all privileges for the 'root' user with the IP.
You can do so by calling:
GRANT ALL PRIVILEGES ON . TO 'root'@'x.x.x.x' IDENTIFIED BY 'the_password' WITH GRANT OPTION;
where x.x.x.x is the source IP (if mysql and tomcat are on the same server, and it's an Amazon EC2 instance, make sure to execute that query with the private ip of your EC2 instance as well as the private DNS, like ip-x-x-x-x.ec2.internal).
In the end, the granted users in your MySQL database should be 'root' from hosts: 127.0.0.1 / localhost / ::1 / your EC2 private IP / your EC2 private DNS (and other external IPs if you plan on calling it from outside the localhost).
Hope it helps. Max