Grails request parameters encoding issue in Tomcat

You need to add URIEncoding='UTF-8' to the Connector elements in conf/server.xml, e.g.

<Connector port='8080' protocol='HTTP/1.1' connectionTimeout='20000'
           redirectPort='8443' URIEncoding='UTF-8' />

This is described here: https://wiki.apache.org/tomcat/FAQ/CharacterEncoding