13、文件下载
程序员文章站
2022-06-03 10:21:14
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什么是文件下载
将服务器上的一个文件,通过流写入到客户端。
文件下载的方式:
- 使用超链接的方式实现文件下载
- 通过手动编写代码的方式实现文件下载
- 设置两个头和一个流
- Content-Type:文件的MIME类型
- Content-Disposition:浏览器支持该格式的文件,提示下载
- 设置代表该文件的输入流(输出流是固定的response.getOutputStream)
文件下载——超链接
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>文件下载:超链接</h1>
<h3><a href="${ pageContext.request.contextPath }/download/qwe.txt">qwe.txt</a></h3>
<h3><a href="${ pageContext.request.contextPath }/download/qweqweqwe.pptx">qwe.pptx</a></h3>
</body>
</html>
文件下载——手动编码
- 文件下载页面准备
<h1>文件下载:手动编码</h1>
<h3><a href="${ pageContext.request.contextPath }/DownloadServlet?filename = qwe.txt">qwe.txt</a></h3>
<h3><a href="${ pageContext.request.contextPath }/DownloadServlet?filename = qweqweqwe.pptx">qwe.pptx</a></h3>
- 文件下载的Servlet
/**
* 文件下载的Servlet
*/
public class DownloadServlet extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//接收参数
String filename = request.getParameter("filename");
//下载,设置两个头一个流
//1、设置Content-Type
String type = getServletContext().getMimeType(filename);
response.setContentType(type);
//2、设置Content-Disposition
response.setHeader("Content-Disposition", "attachment;filename="+filename);
//3、设置一个代表了文件的输入流
String path = getServletContext().getRealPath("/download");
InputStream is = new FileInputStream(path+"/"+filename);
OutputStream os = response.getOutputStream();
//4、两个流对接
int len =0;
byte[] b = new byte[1024];
while((len = is.read(b)) != -1) {
os.write(b,0,len);
}
is.close();
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
中文文件下载
不同浏览器对中文文件下载的编码不一样。
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//接收参数
String filename = new String(request.getParameter("filename").getBytes("ISO-8859-1"),"UTF-8");
//下载,设置两个头一个流
//1、设置Content-Type
String type = getServletContext().getMimeType(filename);
response.setContentType(type);
//2、设置Content-Disposition
response.setHeader("Content-Disposition", "attachment;filename="+filename);
//定义一个代表该文件的路径:
String path = getServletContext().getRealPath("/download");
File file = new File(path+"/"+filename);
//判断浏览器类型
String agent = request.getHeader("User-Agent");
if(agent.contains("Firefox")) {
//filename = base64的解码方式
}else {
//ie或其他浏览器
filename = URLEncoder.encode(filename,"UTF-8");
}
//3、设置一个代表了文件的输入流
InputStream is = new FileInputStream(file);
OutputStream os = response.getOutputStream();
//4、两个流对接
int len =0;
byte[] b = new byte[1024];
while((len = is.read(b)) != -1) {
os.write(b,0,len);
}
is.close();
}
给定目录下的文件下载
需求描述:
给定一个目录,将这个路径中的文件显示到页面上,在页面上给每个文件都提供响应下载的链接,点击链接下载。
文件列表显示(树形遍历)(downlist.jsp):
<%@page import="java.io.File"%>
<%@page import="java.util.LinkedList"%>
<%@page import="java.util.Queue"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<h1>树形遍历</h1>
<%
//1、创建一个队列
Queue<File> queue = new LinkedList<File>();
//2、先将根节点入队
File root = new File("D://CloudMusic");
queue.offer(root);
//判断这个队列是否为空,不为空需要进行遍历:
while(!queue.isEmpty()){
//将根节点出队
File file = queue.poll();
//获得根节点下的子节点
File[] files = file.listFiles();
//遍历子节点
for(File f:files){
//判断该节点是否为叶子节点
if(f.isFile()){
%>
<h4><a href="${ pageContext.request.contextPath }/DownloadListServlet?filename = <%f.getCanonicalPath();%>"><%= f.getName() %></a></h4>
<%
}else{
queue.offer(f);
}
}
}
%>
</body>
</html>
文件下载(DownloadListServlet):
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//接收参数
String path = request.getParameter("filename");
if(path != null) {
path = new String(path.getBytes("ISO-8859-1"),"UTF-8");
}
File file = new File(path);
//实现文件下载
//设置两个头一个流
//获得文件名
String filename = file.getName();
response.setContentType(getServletContext().getMimeType(filename));
//设置另一个头
String agent = request.getHeader("User-Agent");
if(agent.contains("Firefox")) {
//base64转码
}else {
filename = URLEncoder.encode(filename,"UTF-8"); //url编码会将空格变成+
filename = filename.replace("+", " ");
}
response.setHeader("Content-Disposition", "attachment;filename="+filename);
//设置输入流
InputStream is = new FileInputStream(file);
OutputStream os = response.getOutputStream();
//流对接
int len = 0;
byte[] b = new byte[1024];
while((len = is.read(b)) != -1) {
os.write(b,0,len);
}
is.close();
}