Servlet上传文件
1、准备工作
（1）利用FileUpload组件上传文件，需要到apache上下载commons-fileupload-1.3.1.jar
下载地址：http://commons.apache.org/fileupload/
（2）由于文件上传还得有IO流传输，需要到apache上下载commons-io-2.4.jar
下载地址：http://commons.apache.org/io/
2、正式开发
（1）新建文件上传界面
file.jsp：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>上传文件前</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
</head>
<body>
<form action="FileUploadServlet" method="post" enctype="multipart/form-data">
<table>
<tr>
<td>
<label for="username">用户名：</label>
<input type="text" name="username"/>
</td>
</tr>
<tr>
<td>
<label for="password">密 码：</label>
<input type="password" name="password"/>
</td>
</tr>
<tr>
<td>
<input type="file" name="fileOne" id="fileOne"/>
</td>
</tr>
<tr>
<td>
<input type="file" name="fileTwo" id="fileTwo"/>
</td>
</tr>
<tr>
<td>
<input type="submit" name="submit" id="submit" value="提交"/>
<input type="reset" name="reset" id="reset" value="重置"/>
</td>
</tr>
</table>
</form>
</body>
</html>
（2）新建文件上传成功界面
result.jsp：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>上传文件成功</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
</head>
<body>
用户名:<%= request.getAttribute("username") %><br/>
密 码:<%= request.getAttribute("password") %><br/>
文件一:<%= request.getAttribute("fileOne") %><br/>
文件二:<%= request.getAttribute("fileTwo") %><br/>
</body>
</html>
（3）新建servlet进行文件上传处理
FileUploadServlet.java：
package com.you.file.servlet;
import java.io.File;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletContext;
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 FileUploadServlet extends HttpServlet
{
/**
* @Fields serialVersionUID:
*/
private static final long serialVersionUID = -3788743064732005240L;
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
/**
* 设置编码格式
*/
request.setCharacterEncoding("UTF-8");
/**
* 创建一个工厂类
*/
DiskFileItemFactory factory = new DiskFileItemFactory();
ServletContext context = getServletContext();
String path = context.getRealPath("/file");
/**
* 设置上传文件放在磁盘上的临时目录
*/
factory.setRepository(new File(path));
/**
* 设置上传文件大小
*/
factory.setSizeThreshold(1024*1024);
//上传对象
ServletFileUpload fileuplod = new ServletFileUpload(factory);
try
{
/**
* 解析各个表单域
*/
List<FileItem> list = fileuplod.parseRequest(request);
for(FileItem item : list)
{
/**
* 判断是简单域 (item.isFormField()==true)
*/
if(item.isFormField())
{
//获得简单域的名字
String fieldName = item.getFieldName();
//获得简单域的值
String fieldValue = item.getString("UTF-8");
request.setAttribute(fieldName, fieldValue);
}
else//判断是文件域 (item.isFormField()==false)
{
//获得文件域的名字
String fieldName = item.getFieldName();
//获得文件域的值，带路径，即是路径+文件名
String value = item.getName();
//取的文件域的值的名字，不带路径
int temp = value.lastIndexOf("\");
String fieldValue = value.substring(temp+1);
//获得是file文件的内容
request.setAttribute(fieldName, fieldValue);
//写入
item.write(new File(path,fieldValue));
}
}
}
catch (Exception e)
{
//e.printStackTrace();
}
/**
* 跳转到上传成功界面
*/
request.getRequestDispatcher("result.jsp").forward(request, response);
}
/**
* Initialization of the servlet. <br>
* init方法
* @throws ServletException if an error occurs
*/
public void init() throws ServletException
{
}
/**
* destroy方法
* Destruction of the servlet. <br>
*/
public void destroy()
{
super.destroy();
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
* doGet方法
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
this.doPost(request, response);
}
}
（3）配置web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
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_3_0.xsd">
<display-name></display-name>
<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>FileUploadServlet</servlet-name>
<servlet-class>com.you.file.servlet.FileUploadServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>FileUploadServlet</servlet-name>
<url-pattern>/FileUploadServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
3、过程演示
（1）初始化时
（2）输入用户名、密码，上传文件
（3）还未上传，项目中的file文件夹
（4）上传成功后，页面显示
（5）上传成功后，file文件夹
