I want to allow customer type there username (j_username) in there native language. To do this I need to set request encoding to UTF-8. For rest of application it is done via Filter. But for j_security_check Tomcat 5 (and Jetty 4, 5) doesn't call filters BEFORE invocation of FormAuthentifcator.
Actually I solved this problem by modifying org.apache.catalina.authenticator.FormAuthenticator. I add request.setCharacterEncoding("UTF-8") in authenticate() method (same trick works and for Jetty). But prefer less or more standard way.