纯JSP页面处理下载

<%@page language="java" contentType="application/x-msdownload"    pageEncoding="gb2312" import="java.util.*,java.io.*"%>
<%
      //关于文件下载时采用文件流输出的方式处理：
      //加上response.reset()，并且所有的％>后面不要换行，包括最后一个；   
    
      //文件路径
      //跳转前是String file = request.getSession().getServletContext().getRealPath("/");
      String filepath = "";
      if (request.getAttribute("filepath") != null) filepath = request.getAttribute("filepath").toString();
      filepath=filepath.replaceAll("\\\\","/");
     
      //下载的文件名
      String downname=(String)request.getAttribute("downname");
    //response.reset();//可以加也可以不加
      out.clear();
      out=pageContext.pushBody(); 
      
      response.setContentType("application/x-download");
      String filedownload = filepath;
      String filedisplay = downname;
      filedisplay = java.net.URLEncoder.encode(filedisplay,"UTF-8");
      response.addHeader("Content-Disposition","attachment;filename=" + filedisplay);

      OutputStream outp = null;
      FileInputStream in = null;
      try
      {
          outp = response.getOutputStream();
          in = new FileInputStream(filedownload);

          byte[] b = new byte[1024];
          int i = 0;

          while((i = in.read(b)) > 0)
          {
              outp.write(b, 0, i);
          }
          outp.flush();
      }
      
      
      catch(Exception e){
    	  System.out.println("Error!");
      }finally{
          if(in != null){
              in.close();
              in = null;
          }
          if(outp != null){
              outp.close();
              outp = null;
          }
      }
%>