关于jsp中的文件下载

package cn.jbit.download.servlet;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DownloadServlet extends HttpServlet {

private static final long serialVersionUID = 6765085208899952414L;

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String filedownload = "/upload/1/10213.jpg";//即将下载的文件的相对路径
String filedisplay = "10213.jpg";//下载文件时显示的文件保存名称
response.setContentType("application/x-download");//设置为下载application/x-download
//response.setContentType("application/x-msdownload");//设置为下载application/x-msdownload
//response.setContentType("application/octet-stream");//设置为下载application/octet-stream
response.addHeader("Content-Disposition", "attachment;filename="
+ filedisplay);

try {
RequestDispatcher rd = request.getRequestDispatcher(filedownload);
if(rd != null)
{
rd.forward(request,response);
}
response.flushBuffer();
} catch (Exception e) {
e.printStackTrace();
}
}
}

package cn.jbit.download.servlet;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DownloadOfIOServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String basePath = request.getSession().getServletContext().getRealPath("/upload");

String filedisplay = "helloworld.jpg";
String filedownload = basePath + File.separator + "helloworld.jpg";
response.setContentType("applicaiton/x-download");
response.addHeader("Content-Disposition", "attachment;filename="+filedisplay);

InputStream is = null;
OutputStream os = null;
BufferedInputStream bis = null;
BufferedOutputStream bos = null;

is = new FileInputStream(new File(filedownload));
bis = new BufferedInputStream(is);
os = response.getOutputStream();
bos = new BufferedOutputStream(os);

byte[] b = new byte[1024];
int len = 0;
while((len = bis.read(b)) != -1){
bos.write(b,0,len);
}

bis.close();
is.close();
bos.close();
os.close();
}
}