Java 文件上传实例
Apache Commons FileUpload实现文件上传
将Apache的commons-fileupload.jar放在应用程序的WEB-INF\lib下，即可使用。下面举例介绍如何使用它的文件上传功能。
所使用的fileUpload版本为1.2，环境为Eclipse3.3+MyEclipse6.0。FileUpload 是基于 Commons IO的，所以在进入项目前先确定Commons IO的jar包（本文使用commons-io-1.3.2.jar）在WEB-INF\lib下。
此文作示例工程可在文章最后的附件中下载。
示例1
最简单的例子，通过ServletFileUpload静态类来解析Request，工厂类FileItemFactory会对mulipart类的表单中的所有字段进行处理，不只是file字段。getName（）得到文件名，getString（）得到表单数据内容，isFormField（）可判断是否为普通的表单项。
demo1.html
<html><head> <meta http-equiv="Content-Type" content="text/html; charset=GB18030"> <title>File upload</title></head><body> //必须是multipart的表单数据。 <form name="myform" action="demo1.jsp" method="post" enctype="multipart/form-data"> Your name: <br> <input type="text" name="name" size="15"><br> File:<br> <input type="file" name="myfile"><br> <br> <input type="submit" name="submit" value="Commit"> </form></body></html>
<%@ page language="java" contentType="text/html; charset=GB18030" pageEncoding="GB18030"%><%@ page import="org.apache.commons.fileupload.*"%><%@ page import="org.apache.commons.fileupload.servlet.*"%><%@ page import="org.apache.commons.fileupload.disk.*"%><%@ page import="java.util.*"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><% boolean isMultipart = ServletFileUpload.isMultipartContent(request);//检查输入请求是否为multipart表单数据。 if (isMultipart == true) { FileItemFactory factory = new DiskFileItemFactory();//为该请求创建一个DiskFileItemFactory对象，通过它来解析请求。执行解析后，所有的表单项目都保存在一个List中。 ServletFileUpload upload = new ServletFileUpload(factory); List<FileItem> items = upload.parseRequest(request); Iterator<FileItem> itr = items.iterator(); while (itr.hasNext()) { FileItem item = (FileItem) itr.next(); //检查当前项目是普通表单项目还是上传文件。 if (item.isFormField()) {//如果是普通表单项目，显示表单内容。 String fieldName = item.getFieldName(); if (fieldName.equals("name")) //对应demo1.html中type="text" name="name" out.print("the field name is" + item.getString());//显示表单内容。 out.print("<br>"); } else {//如果是上传文件，显示文件名。 out.print("the upload file name is" + item.getName()); out.print("<br>"); } } } else { out.print("the enctype must be multipart/form-data"); }%><html><head> <meta http-equiv="Content-Type" content="text/html; charset=GB18030"> <title>File upload</title></head><body></body></html><html><head> <meta http-equiv="Content-Type" content="text/html; charset=GB18030"> <title>File upload</title></head><body> <form name="myform" action="demo2.jsp" method="post" enctype="multipart/form-data"> File1:<br> <input type="file" name="myfile"><br> File2:<br> <input type="file" name="myfile"><br> <br> <input type="submit" name="submit" value="Commit"> </form></body></html>
<%@ page language="java" contentType="text/html; charset=GB18030" pageEncoding="GB18030"%><%@ page import="org.apache.commons.fileupload.*"%><%@ page import="org.apache.commons.fileupload.servlet.*"%><%@ page import="org.apache.commons.fileupload.disk.*"%><%@ page import="java.util.*"%><%@ page import="java.io.*"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><%String uploadPath="D:\\temp"; boolean isMultipart = ServletFileUpload.isMultipartContent(request); if(isMultipart==true){ try{ FileItemFactory factory = new DiskFileItemFactory(); ServletFileUpload upload = new ServletFileUpload(factory); List<FileItem> items = upload.parseRequest(request);//得到所有的文件 Iterator<FileItem> itr = items.iterator(); while(itr.hasNext()){//依次处理每个文件 FileItem item=(FileItem)itr.next(); String fileName=item.getName();//获得文件名，包括路径 if(fileName!=null){ File fullFile=new File(item.getName()); File savedFile=new File(uploadPath,fullFile.getName()); item.write(savedFile); } } out.print("upload succeed"); } catch(Exception e){ e.printStackTrace(); } } else{ out.println("the enctype must be multipart/form-data"); }%><html><head><meta http-equiv="Content-Type" content="text/html; charset=GB18030"><title>File upload</title></head><body></body></html><html><head> <meta http-equiv="Content-Type" content="text/html; charset=GB18030"> <title>File upload</title></head><body> <form name="myform" action="demo3.jsp" method="post" enctype="multipart/form-data"> File:<br> <input type="file" name="myfile"><br> <br> <input type="submit" name="submit" value="Commit"> </form></body></html>
<%@ page language="java" contentType="text/html; charset=GB18030" pageEncoding="GB18030"%><%@ page import="org.apache.commons.fileupload.*"%><%@ page import="org.apache.commons.fileupload.servlet.*"%><%@ page import="org.apache.commons.fileupload.disk.*"%><%@ page import="java.util.*"%><%@ page import="java.io.*"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><% File uploadPath = new File("D:\\temp");//上传文件目录 if (!uploadPath.exists()) { uploadPath.mkdirs(); } // 临时文件目录 File tempPathFile = new File("d:\\temp\\buffer\"); if (!tempPathFile.exists()) { tempPathFile.mkdirs(); } try { // Create a factory for disk-based file items DiskFileItemFactory factory = new DiskFileItemFactory(); // Set factory constraints factory.setSizeThreshold(4096); // 设置缓冲区大小，这里是4kb factory.setRepository(tempPathFile);//设置缓冲区目录 // Create a new file upload handler ServletFileUpload upload = new ServletFileUpload(factory); // Set overall request size constraint upload.setSizeMax(4194304); // 设置最大文件尺寸，这里是4MB List<FileItem> items = upload.parseRequest(request);//得到所有的文件 Iterator<FileItem> i = items.iterator(); while (i.hasNext()) { FileItem fi = (FileItem) i.next(); String fileName = fi.getName(); if (fileName != null) { File fullFile = new File(fi.getName()); File savedFile = new File(uploadPath, fullFile .getName()); fi.write(savedFile); } } out.print("upload succeed"); } catch (Exception e) { e.printStackTrace(); }%><html><head><meta http-equiv="Content-Type" content="text/html; charset=GB18030"><title>File upload</title></head><body></body></html>package com.zj.sample; import java.io.File;import java.io.IOException;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.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload; @SuppressWarnings("serial")public class Upload extends HttpServlet { private String uploadPath = "D:\\temp"; // 上传文件的目录 private String tempPath = "d:\\temp\\buffer\"; // 临时文件目录 File tempPathFile; @SuppressWarnings("unchecked") public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { try { // Create a factory for disk-based file items DiskFileItemFactory factory = new DiskFileItemFactory(); // Set factory constraints factory.setSizeThreshold(4096); // 设置缓冲区大小，这里是4kb factory.setRepository(tempPathFile);// 设置缓冲区目录 // Create a new file upload handler ServletFileUpload upload = new ServletFileUpload(factory); // Set overall request size constraint upload.setSizeMax(4194304); // 设置最大文件尺寸，这里是4MB List<FileItem> items = upload.parseRequest(request);// 得到所有的文件 Iterator<FileItem> i = items.iterator(); while (i.hasNext()) { FileItem fi = (FileItem) i.next(); String fileName = fi.getName(); if (fileName != null) { File fullFile = new File(fi.getName()); File savedFile = new File(uploadPath, fullFile.getName()); fi.write(savedFile); } } System.out.print("upload succeed"); } catch (Exception e) { // 可以跳转出错页面 e.printStackTrace(); } } public void init() throws ServletException { File uploadFile = new File(uploadPath); if (!uploadFile.exists()) { uploadFile.mkdirs(); } File tempPathFile = new File(tempPath); if (!tempPathFile.exists()) { tempPathFile.mkdirs(); } }}<html><head> <meta http-equiv="Content-Type" content="text/html; charset=GB18030"> <title>File upload</title></head><body>// action="fileupload"对应web.xml中<servlet-mapping>中<url-pattern>的设置. <form name="myform" action="fileupload" method="post" enctype="multipart/form-data"> File:<br> <input type="file" name="myfile"><br> <br> <input type="submit" name="submit" value="Commit"> </form></body></html>
<servlet> <servlet-name>Upload</servlet-name> <servlet-class>com.zj.sample.Upload</servlet-class></servlet> <servlet-mapping> <servlet-name>Upload</servlet-name> <url-pattern>/fileupload</url-pattern></servlet-mapping>