网上相关的例子比较多，这里只给出最简单的一个，使用commons-fileupload组件完成上传。首先你需要下载组件，按说从官网上下载文件应该就可以了，不过貌似最新的这个少了一个jar包，所以我往网盘里传了一份，大家自行下载： http://u.115.com/file/f4694e2ffc http://u.115.com/file/f4e87888d0 ，把这俩文件放到工程WEN-INF的lib目录下。
首先建立一个Servlet：UploadServlet.java:
.. code:: java
package com.web;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.*;
import java.util.*;
import java.io.*;
import org.apache.commons.fileupload.servlet.*;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
/**
* 上传文件的Servlet
* @author 胡阳
*
*/
public class UploadServlet extends HttpServlet {
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
System.out.println("dddd");
res.setContentType("text/html; charset=GB18030");
PrintWriter out = res.getWriter();
System.out.println(req.getContentLength());
System.out.println(req.getContentType());
DiskFileItemFactory factory = new DiskFileItemFactory();
// 允许设置内存中存储数据的门限，单位：字节
factory.setSizeThreshold(4096);
// 如果文件大小大于SizeThreshold，则保存到临时目录
factory.setRepository(new File("D:\\"));
ServletFileUpload upload = new ServletFileUpload(factory);
// 最大上传文件，单位：字节
upload.setSizeMax(1000000);
try {
List fileItems = upload.parseRequest(req);
Iterator iter = fileItems.iterator();
if (iter.hasNext()) {
FileItem item = (FileItem) iter.next();
String fileName = item.getName();
// 忽略其他不是文件域的所有表单信息
if (!item.isFormField()) {
try {
//取得文件名
fileName = fileName.substring(fileName.lastIndexOf("\\") + 1, fileName.length());
// 保存上传的文件到指定的目录指定文件名中
item.write(new File("D:\\",fileName));
} catch (Exception e) {
out.println(e);
}
} else {
throw new IOException("fail to upload");
}
}
} catch (FileUploadException e) {
out.println(e);
}
}
}然后是web.xml文件：
::
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:javaee="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<servlet>
<servlet-name>UploadServlet</servlet-name>
<servlet-class>com.web.UploadServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>UploadServlet</servlet-name>
<url-pattern>/servlet/UploadServlet</url-pattern>
</servlet-mapping>
</web-app>上传文件的页面：upload.jsp
::
<%@ page language="java" contentType="text/html; charset=GB18030"
pageEncoding="GB18030"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GB18030">
<title>Insert title here</title>
</head>
<body>
//注意action地址，还有enctype要写成multipart/form-data，和method="POST"
<form name="uploadform" method="POST" action="./servlet/UploadServlet" ENCTYPE="multipart/form-data">
<table border="1" width="450" cellpadding="4" cellspacing="2" bordercolor="#9BD7FF">
<tr>
<td width="100%" colspan="2">
文件：<input name="x" size="40" type="file">
</td>
</tr>
</table>
<br/><br/>
<table>
<tr><td align="center"><input name="upload" type="submit" value="开始上传"/></td></tr>
</table>
</form>
</body>
</html>更多内容可以参考这里：http://www.blogjava.net/freeman1984/archive/2007/09/28/149358.html
- from the5fire.com
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