java web response提供文件下载功能的实例讲解

2021-03-23 14:07骏马金龙 JAVA教程

下面小编就为大家分享一篇java web response提供文件下载功能的实例讲解，具有很好的参考价值，希望对大家有所帮助。一起跟随小编过来看看吧

webapp项目的结构如下图：

download.html文件的内容如下：

									<!DOCTYPE html>

									<html>

									<head>

									<meta charset="UTF-8">

									<title>Insert title here</title>

									</head>

									<body>

									 <h1>资源下载:</h1>

									 <p> 单纯地使用a标签时，只有浏览器不能解析的文件才会是下载，否则将被浏览器直接解析。</p>

									 <a href="/WEB/resource/a.mp3" rel="external nofollow" >a.mp3</a><br>

									 <a href="/WEB/resource/a.exe" rel="external nofollow" >a.exe</a><br>

									 <a href="/WEB/resource/a.txt" rel="external nofollow" >a.txt</a><br>

									 <a href="/WEB/resource/a.xlsx" rel="external nofollow" >a.xlsx</a><br>

									 <a href="/WEB/resource/a.png" rel="external nofollow" >a.png</a><br>

									 <p>因此，使用a标签结合servlet的response指示浏览器不解析这些待下载文件</p>

									 <a href="/WEB/download?filename=a.mp3" rel="external nofollow" >a.mp3</a><br>

									 <a href="/WEB/download?filename=a.exe" rel="external nofollow" >a.exe</a><br>

									 <a href="/WEB/download?filename=a.txt" rel="external nofollow" >a.txt</a><br>

									 <a href="/WEB/download?filename=a.xlsx" rel="external nofollow" >a.xlsx</a><br>

									 <a href="/WEB/download?filename=a.png" rel="external nofollow" >a.png</a><br>

									</body>

									</html>

负责处理下载的Servlet——download.java文件的内容如下：

									package com.download.servlet;

									import java.io.FileInputStream;

									import java.io.IOException;

									import java.io.InputStream;

									import javax.servlet.ServletException;

									import javax.servlet.ServletOutputStream;

									import javax.servlet.http.HttpServlet;

									import javax.servlet.http.HttpServletRequest;

									import javax.servlet.http.HttpServletResponse;

									/**

									 * Servlet implementation class Download

									 */

									public class Download extends HttpServlet {

									 private static final long serialVersionUID = 1L;

									 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

									 //1.获取请求下载的文件名

									 String filename = request.getParameter("filename");

									 //2.获取文件的文件系统路径

									 String filePath = request.getServletContext().getRealPath("resource/"+filename);

									 //3.设置响应头，提示浏览器不要解析响应的文件数据，而是以附件(attachment)的形式解析，即下载功能

									 response.setContentType(this.getServletContext().getMimeType(filename));

									 response.setHeader("Content-Disposition", "attachment;filename="+filename);

									 //4.读取文件的 输入流，以及响应的输出流，并将数据输出给客户端

									 InputStream in = new FileInputStream(filePath);

									 ServletOutputStream out = response.getOutputStream();

									 int len = 0;

									 byte[] buf = new byte[1024];

									 while((len=in.read(buf))!=-1) {

									  out.write(buf, 0, len);

									 }

									 in.close();

									 }

									 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

									 doGet(request, response);

									 }

									}