Servlet實現web站點文件下載功能示例
2018-07-20 來源：open-open
1、首先創(chuàng)建一個SharedFilesServlet用于返回一個文件分享界面
package com.hyman.view;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class SharedFilesServlet
*/
public class SharedFilesServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public SharedFilesServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType("text/html; charset=utf-8");
PrintWriter out = response.getWriter();
out.println("<script type='text/javascript' language='javascript'>"
+ "function fileDown(obj){"
+ "var resourceName = '';"
+ "var buttonId = obj.getAttribute('id');"
+ "var eleName = buttonId.substring(0,3) + 'File';"
+ "resourceName = document.getElementsByName(eleName)[0].value;"
+ "var url = '/SharingSite/DownFileServlet?fileName=' + resourceName;"
+ "window.location.href=url;"
+ "}"
+ "</script>");
out.println("<h1>文件共享網站</h1>");
out.println("mp3資源：<input type='text' name='mp3File' /> <input type='submit' value ='點擊下載' id='mp3Down' onclick='fileDown(this)' /><br/>");
out.println("avi資源：<input type='text' name='aviFile' /> <input type='submit' value ='點擊下載' id='aviDown' onclick='fileDown(this)' /><br/>");
out.println("jpg資源：<input type='text' name='jpgFile' /> <input type='submit' value ='點擊下載' id='jpgDown' onclick='fileDown(this)' /><br/>");
out.println("txt資源：<input type='text' name='txtFile' /> <input type='submit' value ='點擊下載' id='txtDown' onclick='fileDown(this)' /><br/>");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
this.doGet(request, response);
}
}
2、然后創(chuàng)建一個控制器，來判斷是否盜鏈，以及處理文件下載邏輯：
package com.hyman.controller;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class DownFileServlet
*/
public class DownFileServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public DownFileServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType("text/html; charset=utf-8");
String referer = request.getHeader("Referer");
if (referer == null || !referer.startsWith("http://localhost:8080/SharingSite/")) {
response.sendRedirect("/SharingSite/AntiPirateLink");
} else {
String fileName = request.getParameter("fileName");
response.setHeader("Content-Disposition", "attachment; filename="+fileName);
String path = this.getServletContext().getRealPath("/resources/"+fileName);
FileInputStream fis = null;
OutputStream os = null;
try {
fis = new FileInputStream(new File(path));
byte buff[] = new byte[1024];
int len = 0;
os = response.getOutputStream();
while ((len = fis.read(buff)) > 0) {
os.write(buff, 0, len);
}
} catch (Exception e) {
e.printStackTrace();
throw new RuntimeException();
} finally {
if (os != null) os.close();
if (fis != null) fis.close();
}
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
this.doGet(request, response);
}
}
3、創(chuàng)建一個AntiPirateLink返回盜鏈提醒界面，并在10秒后自動刷新跳轉到SharedFilesServlet
package com.hyman.view;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class AntiPirateLink
*/
public class AntiPirateLink extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public AntiPirateLink() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType("text/html; charset=utf-8");
PrintWriter out = response.getWriter();
out.println("<script type='text/javascript' language='javascript'>"
+ "var i = 10;"
+ "function showTime(){"
+ "if(i > 0) {document.getElementById('time').innerHTML = '請不要盜鏈下載... ' + i +' 秒后自動跳轉到下載首頁...';"
+ "i--;}"
+ "}"
+ "setInterval('showTime()',1000);"
+ "</script>");
out.println("<span id='time'></span>");
response.setHeader("Refresh", "10; url=/SharingSite/SharedFilesServlet");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
this.doGet(request, response);
}
}
【分析】文件下載部分實現步驟：
【分析】文件下載部分實現步驟：1、response.setHeader("Content-Disposition", "attachment; filename="+fileName);在http回復消息頭中的Content-Disposition中指明下文件的文件名；
2、調用this.getServletContext().getRealPath("/resources/"+fileName);函數獲取到文件的全路徑；
3、使用文件流FileInputStream將文件讀入到服務器內存，重要要用到緩存處理，然后再調用response的getOutputStream()方法獲得向客戶端寫文件的輸出文件流；
來自： http://www.cnblogs.com/page-of-Hyman/p/4321523.html
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