JSP/Servlet文件上传下载

来源：互联网发布：电信2.9g网络制式编辑：程序博客网时间：2024/05/16 17:37

文件的上传和下载都是Web应用程序中很常见的功能，比如在论坛中用户可以上传自己的喜欢的头像，邮件系统中用户可以上传附件，到网站上去下载自己喜欢的资源等等。

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

<%@ 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>文件上传</title>  </head>  <body>  <c:if test="${param.code eq '001'}">  <div style="color:red">上传成功！</div>  </c:if>  <c:if test="${param.code eq '002'}">  <div style="color:red">上传失败！</div>  </c:if>    <form action="uploadServlet" method="post" enctype="multipart/form-data">    照片描述：<input type="text" name="desc"/><br/>    <input type="file" name="file1"/><br/>    <input type="submit" value="提交"/>    </form>  </body></html>

uploadServlet.java

import java.io.File;import java.io.IOException;import java.text.SimpleDateFormat;import java.util.Date;import java.util.Iterator;import java.util.List;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.apache.commons.fileupload.FileItem;import org.apache.commons.fileupload.FileUpload;import org.apache.commons.fileupload.disk.DiskFileItemFactory;public class UploadServlet extends HttpServlet {private final String uploadPath = "C:/file/"; // 用于存放上传文件的目录private final String tempPath = "C:/tempFile"; // 用于存放临时文件的目录private final int flushSize = 1024 * 512; // 缓冲区大小private final long fileSize = 10 * 1024 * 1024; // 文件最大大小public void init() throws ServletException {File file = new File(uploadPath);if (!file.exists()) {file.mkdir();}file = new File(tempPath);if (!file.exists()) {file.mkdir();}}public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// 判断from表单的enctype属性值是否设置为multipart/form-databoolean isMultipart = FileUpload.isMultipartContent(request);if (!isMultipart) {return;}try {DiskFileItemFactory factory = new DiskFileItemFactory();// 设置缓冲区大小factory.setSizeThreshold(flushSize);factory.setRepository(new File(tempPath));// 创建FileUpload对象FileUpload upload = new FileUpload(factory);// 设置文件最大大小upload.setSizeMax(fileSize);List items = upload.parseRequest(request);Iterator iter = items.iterator();while (iter.hasNext()) {FileItem item = (FileItem) iter.next();// 判断是否是file表单元素if (!item.isFormField()) {String name = item.getName();//获得文件路径及名称name = name.substring(name.lastIndexOf(File.separator) + 1,name.length());//获得文件名String fileType = name.substring(name.indexOf("."));//获得文件后缀名String filename = getFileName();//随机产生一个文件名防止文件名重复long size = item.getSize();//如果文件名不存在 则不处理if ((name == null || name.equals("")) && size == 0) {continue;}item.write(new File(uploadPath + filename + fileType));} else {//获得文件描述String desc = item.getString("UTF-8");System.out.println(desc);}}response.sendRedirect("upload.jsp?code=001");} catch (Exception e) {e.printStackTrace();response.sendRedirect("upload.jsp?code=002");}}private String getFileName() {//根据时间产生文件名SimpleDateFormat df = new SimpleDateFormat("yyyyMMddhhmmssms");return df.format(new Date());}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

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应用程序以外的目录中。

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>

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);}}