JavaEE实现文件下载

 package com.yyz.response;
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 //文件下载
 public class ResponseDemo extends HttpServlet {
     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         String realpath = this.getServletContext().getRealPath("/download/1.gif");
         String filename = realpath.substring(realpath.lastIndexOf("\\")+1);
         response.setHeader("content-disposition", "attachment;filename="+filename);
         //服务器通过这个头，告诉浏览器以下载方式打开数据
         FileInputStream in = new FileInputStream(realpath);
         int len = 0;
         byte buffer[]=new byte[1024];
         OutputStream out = response.getOutputStream();
         while((len = in.read(buffer))>0){
             out.write(buffer, 0, len);
             }
         in.close();
         //out不用close，response在销毁的时候服务器会自动关闭与response相关的流。
 }
     public void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
            doGet(request,response);
     }
 }

 package com.yyz.response;
 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;
 //中文文件下载时，中文文件名要经过URL编码。
 public class ResponseDemo extends HttpServlet {
     public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         String realpath = this.getServletContext().getRealPath("/download/图片.gif");
         String filename = realpath.substring(realpath.lastIndexOf("\\")+1);
         response.setHeader("content-disposition", "attachment;filename="+URLEncoder.encode(filename,"UTF-8"));
        //本函数将字符串以 URL 编码
         FileInputStream in = new FileInputStream(realpath);
         int len = 0;
         byte buffer[]=new byte[1024];
         OutputStream out = response.getOutputStream();
         while((len = in.read(buffer))>0){
             out.write(buffer, 0, len);
             }
         in.close();
 }
     public void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
            doGet(request,response);
     }
 }