sevlet 给客户端下载一个文件

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package com.itheima.servlet;


import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;


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


public class ServletDemo3 extends HttpServlet {
/*给客户端下载一个文件的思路
* 
* 1.得到文件的路径
* 2.创建一个输出流 把文件放进去
* 3.根据路径得到文件的名字
* 4.用URLEncoder.encode给文件编码
* 5.用setHeader告诉客户端要下载什么文件
* 6.用字节流输出文件
* 
* */
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//通过路径得到一个输入流
String path = this.getServletContext().getRealPath("/WEB-INF/classes/美女.jpg");
FileInputStream fis = new FileInputStream(path);
//创建字节输出流
ServletOutputStream sos = response.getOutputStream();

//得到要下载的文件名
String filename = path.substring(path.lastIndexOf("\\")+1);

//设置文件名的编码
filename = URLEncoder.encode(filename, "UTF-8");//将不安全的文件名改为UTF-8格式

//告知客户端要下载文件
response.setHeader("content-disposition", "attachment;filename="+filename);
response.setHeader("content-type", "image/jpeg");

//执行输出操作
int len = 1;
byte[] b = new byte[1024];
while((len=fis.read(b))!=-1){
sos.write(b,0,len);
}

sos.close();
fis.close();
}


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


}