You would need to send the requests to tomcat, something like this:
location /forums {
proxy_set_header Host $host;
proxy_set_header X-Forwarded-Host $host;
proxy_set_header X-Forwarded-Server $host;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Real-IP $remote_addr;
proxy_pass http://127.0.0.1:8080;
}
You can find documentation for proxy settings here:
http://wiki.nginx.org/NginxHttpProxyModule