@WebFilter(filterName="DownloadFilter", urlPatterns="/content/*")
public class DownloadFilter implements Filter {

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        try {
            String time = servletRequest.getParameter("expiredTime");
            String key = servletRequest.getParameter("key");

            String uri = request.getRequestURI();
            String[] items = uri.split("/");
            String fileName = URLDecoder.decode(items[items.length - 1],"UTF-8");
            if (!FileStoreUtils.validateDownload(fileName,time,key)) {
                throw new IllegalAccessException("key is invalid");
            }

            filterChain.doFilter(request,response);
        } catch (IllegalArgumentException e) {
            response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
        } catch (IllegalAccessException e) {
            response.setStatus(HttpServletResponse.SC_FORBIDDEN);
        } catch (Exception e) {
            response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
        }
    }
 ...
}

<?xml version="1.0" encoding="UTF-8"?>
<Context aliases="/content=D:\myFiles\">

</Context>