servlet 和filter 抛出404等异常

1. servlet抛出错误代码异常，如404

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

2. filter抛出错误代码异常

    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);

}