文件上传Fileupload组件-优快云博客

1.jsp页面：method必须为post,enctype="multipart/form-data"


 <form action="UploadServlet" method="post" enctype="multipart/form-data">

    username: <input type="text" name="username"><br>
    file: <input type="file" name="file"><br>
    file2: <input type="file" name="file2"><br>

    <input type="submit" value="submit">

2 web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
	xmlns="http://java.sun.com/xml/ns/javaee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <servlet>
    <servlet-name>UploadServlet</servlet-name>
    <servlet-class>com.shengsiyuan.servlet.UploadServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>UploadServlet</servlet-name>
    <url-pattern>/UploadServlet</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

3.Servlet处理类：

jar包：
commons-io-2.0.1.jar
commons-fileupload-1.2.2.jar


package com.shengsiyuan.servlet;

import java.io.File;
import java.io.IOException;
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;

public class UploadServlet extends HttpServlet {
	//处理文件上传 使用apache 的 FileUpload组件为Servlet及Web应用提供上传功能
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		/**
		 * 使用FileUpload上传步骤
		 * FileUpload：默认上传文件的大小为10k
		 */
		//步骤一：DiskFileItemFactory 磁盘文件条目工厂
		DiskFileItemFactory factory = new DiskFileItemFactory();
		//upload文件夹为WebRoot下的一个文件夹；
		//path得到该文件夹的绝对路径
		String path = req.getRealPath("/upload");
		//setRepository方法用于设置一个目录：用于临时存放上传的文件
		//如果文件比较小，会直接存在内存里，如果比较大，则需要缓冲放在磁盘上存放（超过）
		factory.setRepository(new File(path));
		//设置文件大小，如果超出，文件会直接被写到磁盘上面 （1M），如果没超出，则存放在内存里
		factory.setSizeThreshold(1024 * 1024);
		//步骤二：ServletFileUpload：创建指定处理上传的对象；提供（parseRequest）方法去解析请求
		ServletFileUpload upload = new ServletFileUpload(factory);

		try {
			//步骤三：FileItem：提供一序列方法
			//list 为上传的多个文件
			List<FileItem> list = (List<FileItem>) upload.parseRequest(req);
			for (FileItem item : list) {
				//取得form input 的name值
				String name = item.getFieldName();
				if (item.isFormField()) {// 这里处理的是普通文本域 input type=text
					//获得name对应input的value值
					String value = item.getString();
					System.out.println(name + "=" + value);
					//放到request范围
					req.setAttribute(name, value);
				} else {// 这里处理文件类型 type=file
					// 获取到上传文件的名字
					String value = item.getName();
					int start = value.lastIndexOf("\\");
					//处理 opera 浏览器会把上传文件的路径都取得，
					String fileName = value.substring(start + 1);
					req.setAttribute(name, fileName);
					// 将文件写到指定磁盘的目录里：路径：path，文件名：fileName
					item.write(new File(path, fileName));
					// 也可由下面的方法写到磁盘			
					// OutputStream os = new FileOutputStream(new File(path,
					// fileName));
					// InputStream is = item.getInputStream();
					// byte[] buffer = new byte[400];
					// int length = 0;
					// while((length = is.read(buffer)) != -1)
					// {
					// os.write(buffer, 0, length);
					// }
					//					
					// is.close();
					// os.close();
				}
			}

		} catch (Exception ex) {
			ex.printStackTrace();
		}
		//将请求转发到页面
		req.getRequestDispatcher("fileUploadResult.jsp").forward(req, resp);
	}
}

4 fileUploadResult.jsp


 <%@ page language="java" import="java.util.*, java.io.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
 <body>
   <%
   /*
   	InputStream is = request.getInputStream();
    BufferedReader br = new BufferedReader(new InputStreamReader(is));
    String buffer = null;
    while(null != (buffer = br.readLine())) {
    	out.print(buffer + "<br>");
    }
    br.close();
    is.close();
   */
   %>
   username : ${requestScope.username }<br>
   file: ${requestScope.file}<br>
   file2: ${requestScope.file2 }<br> 
  </body>