Servlet中的上传下载文件

一、文件上传

文件的上传也是基于表单来完成的，表单中的file元素可以自动生成一个文本框和一个按钮，文本框可以输入本地文件名或路径，点击按钮则可以打开一个文件选择框让用户选中本地文件。需要注意的是在文件上传时还必须设置表单的enctype属性，并将它的值设置为multipart/form-data。

upload.jsp

<FORM METHOD="POST" ENCTYPE="multipart/form-data"

ACTION="SmartUpladServlet.do">

<INPUT TYPE="text" name="userName"><br>

<INPUT TYPE="file" NAME="myFile"><br>

<INPUT TYPE="file" NAME="myFile2"><br>

<INPUT TYPE="file" NAME="myFile3"><br>

<INPUT TYPE="SUBMIT" value="上传">

</FORM>

</body>

采用的是SmartUpload，需要SmartUpload的包。

上传文件的Servlet
import java.io.File;

import java.io.IOException;

import java.io.PrintWriter;

import java.sql.SQLException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.jspsmart.upload.SmartUpload;

import com.jspsmart.upload.SmartUploadException;

public class SmartUpladServlet extends HttpServlet {

public SmartUpladServlet() {

super();

}

public void destroy() {

super.destroy();

}

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

//文件上传个数

int count = 0;

//文件上传地址

String filePath = getServletContext().getRealPath("/")+"smartUpload";

//如果文件夹不存在 则创建这个文件夹

File file = new File(filePath);

if(!file.exists())

{

file.mkdir();

}
//初始化对象

SmartUpload su = new SmartUpload();

su.initialize(getServletConfig(),request,response);

//设置文件最大容量

su.setMaxFileSize(10*1024*1024);

//设置所有文件最大容量

su.setTotalMaxFileSize(100*1024*1024);

//设置上传文件类型

su.setAllowedFilesList("rar,txt,jpg,bmp,gif");

try {

//设置禁止上传的文件类型

su.setDeniedFilesList("jsp,js,html,css");

//上传文件

su.upload();

System.out.println("userName=" + su.getRequest().getParameter("userName"));

count = su.save(filePath);

}

catch (SQLException e) {

e.printStackTrace();

}

catch (SmartUploadException e) {

e.printStackTrace();

}

for (int i = 0; i < su.getFiles().getCount(); i++) {

com.jspsmart.upload.File tempFile = su.getFiles().getFile(i);

System.out.println("表单项名称:" + tempFile.getFieldName());

System.out.println("文件名：" + tempFile.getFileName());

System.out.println("文件长度：" + tempFile.getSize());

System.out.println("文件扩展名:" + tempFile.getFileExt());

System.out.println("文件全名：" + tempFile.getFilePathName());

}

System.out.println("上传成功！共" + count + "个文件！");

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request,response);

}
public void init() throws ServletException {

}

}

web.XML文件配置
<servlet>

<description>This is the description of my J2EE component</description>

<display-name>This is the display name of my J2EE component</display-name>

<servlet-name>SmartUpladServlet</servlet-name>

<servlet-class>com.kay.servlet.SmartUpladServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>SmartUpladServlet</servlet-name>

<url-pattern>/SmartUpladServlet.do</url-pattern>

</servlet-mapping>

二、文件下载

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应用程序外的目录中。

显示文件夹内所有文件的servlet

import java.io.File;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

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>

下载文件的DownLoadServlet

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);

}

}

原帖地址:http://blog.sina.com.cn/s/blog_60f823dd01017nz9.html