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);

}