If you encounter some unexpected error with your web app, the best place to check what’s wrong is Tomcat’s app.log file.
1. Firstly, ssh to the server containing your app:
$ssh -A xxx.dev.XXX ( you can set shortcuts like in this file ~/.ssh/config)
2. Get the root access
$sudo su –
3. Get the tail of the log. Tail command is useful to see the latest log entries and -f helps to keep refreshing it.
$tail -f app.log
Then replicate the bug, you should see the error message there. It can be null pointer exception for instance.