java实现简单的文件下载
文件下载 需要在WebRoot 下创建images文件夹 并且放入test.txt文件 创建jsp文件夹 放入01.jsp
index.jsp 不变 web.xml需要配置servlet 适合初学者研究学习
//index.jsp
<%@ page language="java" import="java.util.*" 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">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!-- <link rel="stylesheet" type="text/css" href="styles.css"> -->
</head>
<body>
<a href="jsp/01.jsp">[下载]</a>
</body>
</html>//jsp文件夹下的01.jsp
<%@ page language="java" import="java.util.*" 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">
<html>
<head>
<base href="<%=basePath%>">
</head>
<body>
下载：<a href="downloadServlet.do?filename=test1.txt">test1.txt</a> ${errorResult}
</body>
</html>
//文件下载serlvet
package com.kero99.ygc.download;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class DownloadServlet extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
//获取文件下载路径
String path = getServletContext().getRealPath("/") + "images/";
String filename = req.getParameter("filename");
File file = new File(path + filename);
if(file.exists()){
//设置相应类型application/octet-stream
resp.setContentType("application/x-msdownload");
//设置头信息 Content-Disposition为属性名 附件形式打开下载文件 指定名称 为 设定的filename
resp.setHeader("Content-Disposition", "attachment;filename=\"" + filename + "\"");
//输入流写入输出流
InputStream inputStream = new FileInputStream(file);
ServletOutputStream ouputStream = resp.getOutputStream();
byte b[] = new byte[1024];
int n ;
//循环读取 !=-1读取完毕
while((n = inputStream.read(b)) != -1){
//写入到输出流 从0读取到n
ouputStream.write(b,0,n);
}
//关闭流、释放资源
ouputStream.close();
inputStream.close();
}else{
req.setAttribute("errorResult", "文件不存在下载失败！");
RequestDispatcher dispatcher = req.getRequestDispatcher("jsp/01.jsp");
dispatcher.forward(req, resp);
}
}
public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doGet(req,resp);
}
}
//web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>20170428_V1.0_download</display-name>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>DownloadServlet</servlet-name>
<servlet-class>com.kero99.ygc.download.DownloadServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DownloadServlet</servlet-name>
<url-pattern>/downloadServlet.do</url-pattern>
</servlet-mapping>
</web-app>