It is because the tomcat uses ISO-8859-1 as the default encoding...
Solutions:
1. By declaring page directive
<%@ page contentType="text/html;charset=UTF-8"%>
OR
2. Set the encoding before calling request.getParameter("XXX") in the page
<%
request.setCharacterEncoding("UTF-8");
request.getParameter("XXX");
request.getParameter("YYY");
%>