WicketFilter.java line 194 invokes getLastModified() which invokes "request.getParameterMap()" on line 962. Later on in that same request, WicketFilter.java line 222 invokes doGet() which invokes response.setCharacterEncoding() on line 376.
This is just one case where this problem occurs but I believe others might exist. Whenever Wicket violates the standard Glassfish spews out this warning:
PWC4011: Unable to set request character encoding to UTF-8 from context <context-path>, because request parameters have already been read, or ServletRequest.getReader() has already been called
... you literally end up with tens of these warnings per request, and supposedly, the wrong behavior Glassfish's FAQ discusses this in more detail: http://wiki.glassfish.java.net/Wiki.jsp?page=FaqWebAppUnableToSetRequestCharEncoding