commons-fileupload-1.2.1实现文件上传

在java里实现文件上传的组件好多，如jspSmartUpload、commons-fileupload，但是jspSmartUpload差不多淘汰了。
在网上找了下 apache的commons-fileupload相关的使用，调通了程序，放在这里以后好直接使用。。
用到的jar包：（到www.apache.org下载即可）
commons-fileupload-1.2.1.jar
commons-io-1.4.jar
网上还有更详细的用法：
http://www.cnblogs.com/yyw84/archive/2007/06/27/797652.html
由于代码太多，如果大家有兴趣，可以自己去参考参考。

这是我自己机器上通过的简单的代码，放在下面：
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>FileUpload</servlet-name>
    <servlet-class>FileUpload.FileUploadServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>FileUpload</servlet-name>
    <url-pattern>/servlet/FileUploadServlet</url-pattern>
</servlet-mapping>

<welcome-file-list>
    <welcome-file>fileUpload.jsp</welcome-file>
</welcome-file-list>
</web-app>



FileUpload.javapackage FileUpload;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
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.FileUploadException;
import org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
public class FileUploadServlet extends HttpServlet {
public FileUploadServlet() {
   super();
}
public void destroy() {
   super.destroy(); // Just puts "destroy" string in log
   // Put your code here
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
   doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
   final String appRealPath = this.getServletContext().getRealPath("/"); //获取web app的物理路径
   final long MAX_SIZE = 3 * 1024 * 1024;    // 设置上传文件最大为 3M
   final String[] allowedExt = new String[] { "jpg", "jpeg", "gif", "txt",
            "doc", "docx", "mp3", "wma", "m4a" };   // 允许上传的文件格式的列表
   response.setContentType("text/html");
   response.setCharacterEncoding("UTF-8");   // 设置字符编码为UTF-8, 这样支持汉字显示
   // 实例化一个硬盘文件工厂,用来配置上传组件ServletFileUpload
   DiskFileItemFactory dfif = new DiskFileItemFactory();
   dfif.setSizeThreshold(4096);    // 设置上传文件时用于临时存放文件的内存大小,这里是4K.多于的部分将临时存在硬盘
   dfif.setRepository(new File(appRealPath + "ImagesUploadTemp//"));
             // 设置存放临时文件的目录,web根目录下的ImagesUploadTemp目录
   // 用以上工厂实例化上传组件
   ServletFileUpload sfu = new ServletFileUpload(dfif);
  
   sfu.setSizeMax(MAX_SIZE);    // 设置最大上传尺寸
   PrintWriter out = response.getWriter();
  
   // 从request得到 所有 上传域的列表  
   List fileList = null;
   try {
    fileList = sfu.parseRequest(request);
   } catch (FileUploadException e) {// 处理文件尺寸过大异常
    if (e instanceof SizeLimitExceededException) {
     out.println("文件尺寸超过规定大小:" + MAX_SIZE + "字节<p />");
     out.println("<a href=/" " + request.getContextPath() + "/fileUpload.jsp" + " /" target=/"_top/">返回</a>");
     return;
    }
    e.printStackTrace();
   }
   // 没有文件上传
   if (fileList == null || fileList.size() == 0) {
    out.println("请选择上传文件<p />");
    out.println("<a href=/" " + request.getContextPath() + "/fileUpload.jsp" + " /" target=/"_top/">返回</a>");
    return;
   }
   // 得到所有上传的文件
   Iterator fileItr = fileList.iterator();
   // 循环处理所有文件
   while (fileItr.hasNext()) {
    FileItem fileItem = null;
    String path = null;
    long size = 0;
    // 得到当前文件
    fileItem = (FileItem) fileItr.next();
    // 忽略简单form字段而不是上传域的文件域(<input type="text" />等)
    if (fileItem == null || fileItem.isFormField()) {
     continue;
    }
    // 得到文件的完整路径
    path = fileItem.getName();
    // 得到文件的大小
    size = fileItem.getSize();
    if ("".equals(path) || size == 0) {
     out.println("请选择上传文件<p />");
     out.println("<a href=/" " + request.getContextPath() + "/fileUpload.jsp" + " /" target=/"_top/">返回</a>");
     return;
    }
    // 得到去除路径的文件名
    String t_name = path.substring(path.lastIndexOf("//") + 1);
    // 得到文件的扩展名(无扩展名时将得到全名)
    String t_ext = t_name.substring(t_name.lastIndexOf(".") + 1);
    // 拒绝接受规定文件格式之外的文件类型
    int allowFlag = 0;
    int allowedExtCount = allowedExt.length;
    for (; allowFlag < allowedExtCount; allowFlag++) {
     if (allowedExt[allowFlag].equals(t_ext))
      break;
    }
    if (allowFlag == allowedExtCount) {
     out.println("请上传以下类型的文件<p />");
     for (allowFlag = 0; allowFlag < allowedExtCount; allowFlag++)
      out.println("*." + allowedExt[allowFlag]
        + "&nbsp;&nbsp;&nbsp;");
     out
       .println("<a href=/" " + request.getContextPath() + "/fileUpload.jsp" + " /" target=/"_top/">返回</a>");
     return;
    }
    long now = System.currentTimeMillis();
    // 根据系统时间生成上传后保存的文件名
    String prefix = String.valueOf(now);
    // 保存的最终文件完整路径,保存在web根目录下的ImagesUploaded目录下
    String u_name = appRealPath + "ImagesUploaded//"
      + prefix + "." + t_ext;
    try {
     // 保存文件
     fileItem.write(new File(u_name));
     out.println("文件上传成功. 已保存为: " + prefix + "." + t_ext
       + " &nbsp;&nbsp;文件大小: " + size + "字节<p />");
     out.println("<a href=/" " + request.getContextPath() + "/fileUpload.jsp" + " /" target=/"_top/">继续上传</a>");
    } catch (Exception e) {
     e.printStackTrace();
    }
   }
}
public void init() throws ServletException {
   // Put your code here
}
}




fileUpload.jsp<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>    
    <title>My JSP 'fileUpload.jsp' starting page</title>
</head>

<body>
<form action="<%= request.getContextPath() %>/servlet/FileUploadServlet" method="post" enctype="multipart/form-data" >
    <input type="file" name="fileUpload" />
    <input type="submit" value="upload" />
</form>
</body>
</html>



记得在上传的form里指明enctype="multipart/form-data"，具体的读一下FileUpload.java就清楚了。