@Override
    public void doHandle(HttpRequest request, HttpResponse response) throws IOException {
        ...
        ...
        ...
       response.setHeader(HttpHeaderConstant.Names.LAST_MODIFIED, sdf.get().format(lastModifyDate));
        
        //************ start:此处为我这边修改的内容 *****************
        response.setHeader(HttpHeaderConstant.Names.CONTENT_LENGTH, file.length()+"");
        //************ end:此处为我这边修改的内容 *****************

        String contentType = Mimetypes.getInstance().getMimetype(file);
        response.setHeader(HttpHeaderConstant.Names.CONTENT_TYPE, contentType + "; charset=utf-8");
        //HEAD不输出内容
        if (HttpMethodEnum.HEAD.getMethod().equals(method)) {
            return;
        }
        ...
        ...
        ...
    }

        response.setHeader(HttpHeaderConstant.Names.CONTENT_LENGTH, file.length()+"");