I need to execute a function before each def in the controller is invoked (before each new request is sent to the server). In this function I will
1) do a session check if valid forward the request to the appropriate action & controller with the params
2) do a sanitization check for user submitted params 

I am aware of per controller interceptor, how can I write a global common interceptor.

how and where can I invoke this function in grails?
Thanks in advance..