java-文件下載技術

文件下載技術其實就是相當於流拷貝

但是要設置http協議：

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

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

//設置HTTP協議響應頭，告訴瀏覽器要用它的下載程序來接收數據(不同的瀏覽器有自己的默認下載程序，如彈出下載窗口或啓動迅雷)。否則就是默認的瀏覽器直接打開瀏覽

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 {
		
		//設置HTTP協議響應頭，告訴瀏覽器要用它的下載程序來接收數據(不同的瀏覽器有自己的默認下載程序，如彈出下載窗口或啓動迅雷)。否則就是默認的瀏覽器直接打開瀏覽
		resp.setContentType("application/force-download");
		
		//設置HTTP協議響應頭，告訴: 文件名+文件類型  
		String nm = "美女.jpg";	//如果文件名要支持中文，得進行編碼
		nm = URLEncoder.encode(nm, "UTF-8"); 
		resp.setHeader("Content-Disposition", "attachment;filename=\""+nm+"\"");
		
		//下載的核心功能: 從服務器本地磁盤把文件數據讀取出來 寫到 resp.getOutputStream()流中
		//imgs/1.jpg
		String path = getServletContext().getRealPath("imgs/1.jpg");//起始位置是WebRoot根目錄--這裏是下載的文件所在的服務器的目錄
		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();
	}

}