Grails is a excellent framework offering very high productivity. The usage of Groovy as the programming language makes Grails a very productive framework.
Grails is notorious for raising a lot of exceptions and some times it is really hard to figure out what really caused the exceptions. A normal exception may be easily 1000 lines and that makes it really hard for figure out where exactly is the cause of the issue.
To add to this, some times we get an exception right when we start running the app.
A good tip, I have noticed in debugging Grails exceptions is that to look for area in our code where an exception occurs. This may some times be the last item on the exception stack. Fixing the issue in our code may very well lead to the exception to disappear.