servlet之文件的上传下载（二）

来源：互联网发布：apache ab 中文参数编辑：程序博客网时间：2024/06/17 09:40

通过超链接下载文件，会暴露了下载文件在服务器中的真实地址，不利于对资源进行安全保护，而且利用超链接下载文件，服务器端得文件只能存放在Web应用程序所在的目录下。

利用程序编码实现下载，可以增加安全机制，比如我们只能让VIP会员下载等等。还可以从任意位置进行下载，我们可以将文件放到Web应用程序以外的目录中。

把文件目录直接暴露给用户是很不安全的。所以要用Servlet来做，而且这样做，文件的存储方式就更丰富了，可以是从文件系统上取来的，也可以是数据库中经过计算生成的，或者从其它什么稀奇古怪的地方取来的。

public class ShowFileServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String path = "c:/file";//声明集合存放目录下所有文件的文件名List<String> fileList = new ArrayList<String>();File folder = new File(path);//判断文件夹是否存在并且是否是一个目录if(folder.exists() && folder.isDirectory()){//获得目录中所有文件及目录File[] files = folder.listFiles();for (File file : files) {//如果是文件if(file.isFile()){//将文件名放入集合中fileList.add(file.getName());}}}request.setAttribute("fileList", fileList);request.getRequestDispatcher("showfile.jsp").forward(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request,response);}}

showfile.jsp

<%@ page language="java" pageEncoding="UTF-8"%><%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <title>显示所有文件</title>  </head>  <body>  请选择您要下载的文件：<br/>    <c:forEach items="${fileList}" var="fileName">    <a href="downLoadServlet?filename=${fileName }">${fileName }</a><br/>    </c:forEach>  </body></html>

DownLoadServlet.java

import java.io.BufferedInputStream;import java.io.BufferedOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;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 request, HttpServletResponse response)throws ServletException, IOException {String path = "C:/file";String fileName = request.getParameter("filename");File file = new File(path + "/" + fileName);//如果文件存在if (file.exists()) {//设置响应类型及响应头response.setContentType("application/x-msdownload");response.addHeader("Content-Disposition", "attachment; filename=\""+ fileName + "\"");//读取文件InputStream inputStream = new FileInputStream(file);BufferedInputStream bis = new BufferedInputStream(inputStream);byte[] bytes = new byte[1024];ServletOutputStream outStream = response.getOutputStream();BufferedOutputStream bos = new BufferedOutputStream(outStream);int readLength = 0;while ((readLength = bis.read(bytes)) != -1) {bos.write(bytes, 0, readLength);}//释放资源inputStream.close();bis.close();bos.flush();outStream.close();bos.close();}}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

阅读全文

0 0