webapp项目的结构如下图：
download.html文件的内容如下：
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<!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>
<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>
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负责处理下载的Servlet——download.java文件的内容如下：
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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);
}
}
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在浏览器地址栏中输入http://localhost:8080/DownloadServlet/download.html。
以上这篇java web response提供文件下载功能的实例讲解就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持服务器之家。
原文链接：https://www.cnblogs.com/f-ck-need-u/archive/2018/01/17/8306816.html