java-文件下载技术

文件下载技术其实就是相当于流拷贝

但是要设置http协议:

resp.setContentType("application/force-download");

resp.setHeader("Content-Disposition", "attachment;filename=***");

//设置HTTP协议响应头,告诉浏览器要用它的下载程序来接收数据(不同的浏览器有自己的默认下载程序,如弹出下载窗口或启动迅雷)。否则就是默认的浏览器直接打开浏览

package cn.hncu.servlet;

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

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

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

	public void doPost(HttpServletRequest request, HttpServletResponse resp)
			throws ServletException, IOException {
		
		//设置HTTP协议响应头,告诉浏览器要用它的下载程序来接收数据(不同的浏览器有自己的默认下载程序,如弹出下载窗口或启动迅雷)。否则就是默认的浏览器直接打开浏览
		resp.setContentType("application/force-download");
		
		//设置HTTP协议响应头,告诉: 文件名+文件类型  
		String nm = "美女.jpg";	//如果文件名要支持中文,得进行编码
		nm = URLEncoder.encode(nm, "UTF-8"); 
		resp.setHeader("Content-Disposition", "attachment;filename=\""+nm+"\"");
		
		//下载的核心功能: 从服务器本地磁盘把文件数据读取出来 写到 resp.getOutputStream()流中
		//imgs/1.jpg
		String path = getServletContext().getRealPath("imgs/1.jpg");//起始位置是WebRoot根目录--这里是下载的文件所在的服务器的目录
		FileInputStream fin = new FileInputStream(path);
		OutputStream out = resp.getOutputStream();
		int len=0;
		byte b[] = new byte[1024];
		while( (len=fin.read(b))!=-1){
			out.write(b,0,len);
		}
		fin.close();
		out.close();
	}

}


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