protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    super.service(request, response);
    System.out.println("Helloservlet.service");
    System.out.println("request = " + request);
    System.out.println("response = " + response);
    String username = request.getParameter("username");
    System.out.println("username = " + username);

    response.setContentType("text/plain");
    response.setCharacterEncoding("utf-8");
    response.getWriter().write("hello " + username );
}

위와 같이 작성하였으며, 콘솔에는 아래와 같이 보이나. 

Helloservlet.service

request = org.apache.catalina.connector.RequestFacade@3561983a

response = org.apache.catalina.connector.ResponseFacade@5c60947

username = "scmoon"

웹브라우져에서는 오류가 납니다. 

Whitelabel Error Page

This application has no explicit mapping for /error, so you are seeing this as a fallback.