javaweb中的文件下载

package cn.itcast.day06.web.servlet;

 

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import java.net.URLEncoder;

 

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

 

public class DownloadServlet extends HttpServlet {

 

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

// 实现防盗链功能

// 获得 referer 头  用于说明来访者来自哪里

String referer = request.getHeader("referer");

if(referer==null || !referer.startsWith("http://localhost")) {

// 是盗链者

response.sendRedirect("/day06/index.jsp");

return ;

}

// 解决response中文乱码问题

response.setContentType("text/html;charset=utf-8"); // 设置消息体的编码

// 通过 http 协议  发送的http响应消息头  不能出现中文  中文必须要经过url编码

String filename = URLEncoder.encode("美女.jpg", "utf-8");

// 通知浏览器以下载的方式读取资源

response.setHeader("content-disposition", "attachment;filename="+filename);

// 读取图片数据  发给ie浏览器

String webPath = "/download/美女.jpg"; // 相当于当前web应用的path

ServletContext servletContext = super.getServletContext();

InputStream in = servletContext.getResourceAsStream(webPath);

OutputStream out = response.getOutputStream();

int len;

byte[] buffer = new byte[1024];

while((len=in.read(buffer))!=-1)

out.write(buffer, 0, len);

}

 

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request, response);

}

 

}