记录3种jsp下载文件的方法

<%
  response.setContentType("application/x-download");//设置为下载application/x-download
  String filedownload = "/要下载的文件名";//即将下载的文件的相对路径
  String filedisplay = "最终要显示给用户的保存文件名";//下载文件时显示的文件保存名称
  String filenamedisplay = URLEncoder.encode(filedisplay,"UTF-8");
  response.addHeader("Content-Disposition","attachment;filename=" + filedisplay);
   
  try
  {
  RequestDispatcher dis = application.getRequestDispatcher(filedownload);
  if(dis!= null)
  {
  dis.forward(request,response);
  }
  response.flushBuffer();
  }
  catch(Exception e)
  {
  e.printStackTrace();
  }
  finally
  {
   
  }
%>

<%@page language="java" contentType="application/x-msdownload" pageEncoding="gb2312"%>
<%
  //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；

  response.reset();//可以加也可以不加
  response.setContentType("application/x-download");

//application.getRealPath("/main/mvplayer/CapSetup.msi");获取的物理路径

String filedownload = "想办法找到要提供下载的文件的物理路径＋文件名";
 String filedisplay = "给用户提供的下载文件名";
  String filedisplay = URLEncoder.encode(filedisplay,"UTF-8");
  response.addHeader("Content-Disposition","attachment;filename=" + filedisplay);

  java.io.OutputStream outp = null;
  java.io.FileInputStream in = null;
  try
  {
  outp = response.getOutputStream();
  in = new FileInputStream(filenamedownload);

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

  while((i = in.read(b)) > 0)
  {
  outp.write(b, 0, i);
  }
//  
outp.flush();
//要加以下两句话，否则会报错
//java.lang.IllegalStateException: getOutputStream() has already been called for //this response  
out.clear();
out = pageContext.pushBody();
}
  catch(Exception e)
  {
  System.out.println("Error!");
  e.printStackTrace();
  }
  finally
  {
  if(in != null)
  {
  in.close();
  in = null;
  }
//这里不能关闭  
//if(outp != null)
  //{
  //outp.close();
  //outp = null;
  //}
  }
%>

<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<a href="do_download.jsp?url=xxxxxx">点击下载 千千动听</a>



<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<%@page import="com.jspsmart.upload.SmartUpload"%>


<%
	
	SmartUpload su=new SmartUpload();
	su.initialize(pageContext);
	su.setContentDisposition(null);//禁止浏览器打开文件 只能下载
	su.downloadFile("upload/1.txt");
	//out.clear();
	//out=pageContext.pushBody();
 %>