方式一：采用RequestDispatcher进行
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/helloworld.jar";//即将下载的文件的相对路径
String filedisplay = "helloworld.jar";//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();
}
}
}
方式二：采用文件流输出的方式下载
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 {
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 basePath = request.getSession().getServletContext().getRealPath("/upload");
//System.out.println(basePath);
String filedisplay = "helloworld.jar";
String filedownload = basePath + File.separator + "helloworld.jar";
System.out.println("----------------------"+filedownload);
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();
}
}
方式三：网页上做超级链接(不推荐使用，样服务器上的目录资源会直接暴露给最终用户)
<a href="/DownloadFile/upload/helloworld.jar">helloworld.jar</a>jsp页面代码：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'download.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
</head>
<body>
下载1<a href="/DownloadFile/upload/helloworld.jar">helloworld.jar</a><br/>
下载2<a href="/DownloadFile/servlet/downloadServlet">helloworld.jar</a><br/>
下载3<a href="/DownloadFile/servlet/downloadOfIOServlet">helloworld.jar</a><br/>
下载4<a href="/DownloadFile/download/filedownload.action">helloworld.jar</a><br/>
</body>
</html>