When I set sourceEncoding to UTF-8 this setting is ignored and groovy script is still compiled probably using platform default encoding.
I can see that sourceEncoding is properly set to UTF-8 in debug log :
[DEBUG]Configuring mojo 'org.codehaus.groovy.maven:gmaven-plugin:1.0-rc-5-kohsuke-1:compile' -->
[DEBUG] (f) sourceEncoding = UTF-8
[DEBUG]-- end configuration –
Strings that originaly contained multi-byte UTF-8 characters are damaged in compiled class file.