前段时间事情比较多，导致二月份没有记录自己的学习情况。最近接触了servlet，参考韩老师的教程自己写了一个web站点文件下载的小项目，该项目中还加入了简单的反盗链技术。
1、首先创建一个SharedFilesServlet用于返回一个文件分享界面
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>文件共享网站</h1>");
out.println("mp3资源：<input type='text' name='mp3File' /> <input type='submit' value ='点击下载' id='mp3Down' onclick='fileDown(this)' /><br/>");
out.println("avi资源：<input type='text' name='aviFile' /> <input type='submit' value ='点击下载' id='aviDown' onclick='fileDown(this)' /><br/>");
out.println("jpg资源：<input type='text' name='jpgFile' /> <input type='submit' value ='点击下载' id='jpgDown' onclick='fileDown(this)' /><br/>");
out.println("txt资源：<input type='text' name='txtFile' /> <input type='submit' value ='点击下载' 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、然后创建一个控制器，来判断是否盗链，以及处理文件下载逻辑：
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、创建一个AntiPirateLink返回盗链提醒界面，并在10秒后自动刷新跳转到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 = '请不要盗链下载... ' + i +' 秒后自动跳转到下载首页...';"
+ "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】文件下载部分实现步骤：
1、response.setHeader("Content-Disposition", "attachment; filename="+fileName);在http回复消息头中的Content-Disposition中指明下文件的文件名；
2、调用this.getServletContext().getRealPath("/resources/"+fileName);函数获取到文件的全路径；
3、使用文件流FileInputStream将文件读入到服务器内存，重要要用到缓存处理，然后再调用response的getOutputStream()方法获得向客户端写文件的输出文件流；