<iframe id='reqFrame' frameborder='0'  style='display:none' allowtransparency='true' ></iframe>

<a  class="easyui-linkbutton" data-options="iconCls:'icon-ok'"  title="/demo/省本部固定资产明细表.xlsx" 
id="btnDown" href="javascript:void(download('btnDown'))" >下载模板</a>

 function download(id){

      $("#reqFrame").attr("src",encodeURI("/servlet/Common?action=downloadByPath&filePath="+$("#"+id).attr("title")));

}

public class SV_Common extends HttpServlet {

    /**

     *

     */

    private static final long serialVersionUID = 1L;

    public static final Logger logger = Logger.getLogger(SV_Common.class

            .getName());

    protected void service(HttpServletRequest request,

            HttpServletResponse response) throws ServletException, IOException {

        String action = request.getParameter("action");

        try {

            if ("downloadByPath".equals(action)) { //下载指定路径的文件

                downloadByPath(request, response);

            } else {

                throw new IllegalArgumentException("没有相匹配的操作类型，请检查opp变量.");

            }

        } catch (Exception ex) {

            ex.printStackTrace();

        }

    }

    private void downloadByPath(HttpServletRequest request,

            HttpServletResponse response) throws IOException, ServletException {

        String filePath = request.getParameter("filePath");

        logger.info("filePath="+filePath);

        String fileFullName = filePath.substring(filePath.lastIndexOf("/") + 1);

        response.reset();

        if (request.getHeader("User-Agent").toLowerCase().indexOf("firefox") > 0) {

            logger.info("User-Agent=firefox");

            response.setHeader(

                    "Content-Disposition",

                    "attachment;filename=" + new String(fileFullName.getBytes("UTF-8"), "ISO8859-1")

                );

        } else {

            logger.info("User-Agent=not firefox");

            response.setHeader(

                    "Content-Disposition",

                    "attachment;filename=" + URLEncoder.encode(fileFullName, "UTF-8")

                );

        }

        File file = new File(PathUtil.getPath("") + "/" + filePath);

        response.setContentType(new MimetypesFileTypeMap().getContentType(file));

        OutputStream out = response.getOutputStream();

        BufferedInputStream in = null;

        byte[] buffer = new byte[8192];

        int length;

        try

        {

            in = new BufferedInputStream(

                new FileInputStream(file),8192

            );

            while ( (length = in.read(buffer)) != -1)

            {

                out.write(buffer, 0 ,length);

            }

        }

        catch (IOException ex)

        {

            ex.printStackTrace();

        }

        finally

        {

            if (out != null)

            {

                try {out.close();}

                catch (IOException ex) {}

                out = null;

            }

            if (in != null)

            {

                try {in.close();}

                catch (IOException ex) {}

                in = null;

            }

        }

        response.flushBuffer();

    };

}