servlet 和filter 抛出404等异常

public void doGet(HttpServletRequest request, HttpServletResponse response) {
    response.sendError(HttpServletResponse.SC_NOT_FOUND);
}

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        HttpServletRequest httpRequest=(HttpServletRequest)request;
        HttpServletResponse httpResponse=(HttpServletResponse)response;

httpResponse.sendError(HttpServletResponse.SC_UNAUTHORIZED);

}