HttpServlet实现下载文件，重要的设置header，否则浏览器无法解析为下载。
Header示例：
1：response.setContentType("application/pdf");//说明实体主体内容的媒体类型
2：response.addHeader("Content-Disposition","attachment; filename=" + URLEncoder.encode(file.getName(), "UTF-8"));//文件解析为下载还是内嵌显示
3：response.setHeader("Content-Length", String.valueOf(length)); //表示实体主体部分的大小
如下示例：
package com.daxin; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.net.URLEncoder; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Servlet implementation class DownLoadFile */ public class DownLoadFile extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public DownLoadFile() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse * response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { File file = new File("C:\Coding\servlet_fie_upload\aa.flv"); if (file.exists()) { FileInputStream in = new FileInputStream(file); // 1:设置http header信息为pdf解析方式 // response.setContentType("application/pdf"); // 1.设置文件ContentType类型，这样设置，会自动判断下载文件类型 response.setContentType("multipart/form-data"); //相对比较通用 response.addHeader("Content-Disposition","attachment; filename=" + URLEncoder.encode(file.getName(), "UTF-8")); response.setHeader("Content-Length", String.valueOf(in.available())); // 2: BufferedInputStream br = null; BufferedOutputStream bw = null; try { br = new BufferedInputStream(in); bw = new BufferedOutputStream(response.getOutputStream()); byte[] buffer = new byte[1024]; int bufferSize = 0; while (-1 != (bufferSize = br.read(buffer))) { bw.write(buffer, 0, bufferSize); } } catch (Exception e) { e.printStackTrace(); } finally { if (bw != null) bw.close(); if (in != null) in.close(); if (br != null) br.close(); } } } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse * response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
1： Web开发中下载文件时,我们一般设置Content-Disposition告诉浏览器下载文件的名称,是否在浏览器中内嵌显示. Content-disposition: inline; filename=foobar.pdf表示浏览器内嵌显示一个文件
2：Content-disposition: attachment; filename=foobar.pdf表示会下载文件
前端页面：
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/"; %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <base href="<%=basePath%>"> <title>Insert title here</title> </head> <body> <a href="DownLoadFile">下载文件</a> </body> </html>