/** * 浏览器能够直接解析的文件如 JPG,avi等资源文件，不包括doc,pdf等 * 取消浏览器页面直接指向TOMCAT服务器的资源进行直接解析，采用下载的方式 */

download.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
   <h1>使用a标签直接指向服务器上的资源</h1>
   <a href="/DownloadFile/download/a.flv">a.flv</a><br>
   <a href="/DownloadFile/download/a.jpg">a.jpg</a><br>
   <a href="/DownloadFile/download/a.mp3">a.mp3</a><br>
   <a href="/DownloadFile/download/a.mp4">a.mp4</a><br>
   <a href="/DownloadFile/download/a.txt">a.txt</a><br>
   <a href="/DownloadFile/download/a.zip">a.zip</a><br>
   <h1>使用服务器端编码的方式实现文件下载</h1>
   <a href="/DownloadFile/downloadServlet?filename=a.flv">a.flv</a><br>
   <a href="/DownloadFile/downloadServlet?filename=a.jpg">a.jpg</a><br>
   <a href="/DownloadFile/downloadServlet?filename=a.mp3">a.mp3</a><br>
   <a href="/DownloadFile/downloadServlet?filename=a.mp4">a.mp4</a><br>
   <a href="/DownloadFile/downloadServlet?filename=a.txt">a.txt</a><br>
   <a href="/DownloadFile/downloadServlet?filename=a.zip">a.zip</a><br>
   <a href="/DownloadFile/downLoadServlet2?filename=美女.jpg">美女.jpg</a><br>
</body>
</html>

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" 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>WEB14</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>

<servlet>
<description></description>
<display-name>DownloadServlet1</display-name>
<servlet-name>DownloadServlet1</servlet-name>
<servlet-class>com.xiangshuai.DownloadServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DownloadServlet1</servlet-name>
<url-pattern>/downloadServlet</url-pattern>
</servlet-mapping>
</web-app>

DownloadServlet.java

package com.xiangshuai;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import sun.misc.BASE64Encoder;

/**
* 浏览器能够直接解析的文件如 JPG,avi等资源文件，不包括doc,pdf等
* 取消浏览器页面直接指向TOMCAT服务器的资源进行直接解析，采用下载的方式
*/
public class DownloadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

/**
* @see HttpServlet#HttpServlet()
*/
public DownloadServlet() {
super();
// TODO Auto-generated constructor stub
}

   /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
   */
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

       request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
String filename = request.getParameter("filename");

//获得请求头中的User-Agent
        String agent = request.getHeader("User-Agent");
        //根据不同浏览器进行不同的编码
        String filenameEncoder = "";
        if (agent.contains("MSIE")) {
            // IE浏览器
            filenameEncoder = URLEncoder.encode(filename, "utf-8");
            filenameEncoder = filenameEncoder.replace("+", " ");
        } else if (agent.contains("Firefox")) {
            // 火狐浏览器
            BASE64Encoder base64Encoder = new BASE64Encoder();
            filenameEncoder = "=?utf-8?B?"
                    + base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
        } else {
            // 其它浏览器
            filenameEncoder = URLEncoder.encode(filename, "utf-8");
        }

   /*要下载的这个文件的类型-----客户端通过文件的MIME类型去区分类型---D:\installation\installation\tomcat8\conf\web.xml
        中crtl+f搜扩展名如 avi,jpg等可以看到扩展名对应的mime-type类型 <mime-mapping>
<extension>jpg</extension>
<mime-type>image/jpeg</mime-type>
</mime-mapping>*/
       response.setContentType(this.getServletContext().getMimeType(filename));
       System.out.println("mimeType:"+request.getServletContext().getMimeType(filename));
       //告诉客户端该文件不是直接解析而是以附件形式打开(下载)----filename="+filename 客户端默认对名字进行解码
       response.setHeader("Content-Disposition", "attachment;filename="+filenameEncoder);

String filePaht = request.getServletContext().getRealPath("download/"+filename);
FileInputStream fileInputStream = new FileInputStream(new File(filePaht));
ServletOutputStream os = response.getOutputStream();
int len=0;byte[] by=new byte[1024];
while((fileInputStream.read(by))!=-1){
   os.write(by, 0, len);
   os.flush();
};
fileInputStream.close();
   }

   /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       // TODO Auto-generated method stub
       doGet(request, response);
   }

}

/** * 浏览器能够直接解析的文件如 JPG,avi等资源文件，不包括doc,pdf等 * 取消浏览器页面直接指向TOMCAT服务器的资源进行直接解析，采用下载的方式 */

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