commons-fileupload-1.2.1實現檔案上傳

在java裡實現檔案上傳的組件好多，如jspSmartUpload、commons-fileupload，但是jspSmartUpload差不多淘汰了。
在網上找了下 apache的commons-fileupload相關的使用，調通了程式，放在這裡以後好直接使用。。
用到的jar包：（到www.apache.org下載即可）
commons-fileupload-1.2.1.jar
commons-io-1.4.jar
網上還有更詳細的用法：
http://www.cnblogs.com/yyw84/archive/2007/06/27/797652.html
由於代碼太多，如果大家有興趣，可以自己去參考參考。

這是我自己機器上通過的簡單的代碼，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("/"); //擷取web app的實體路徑
   final long MAX_SIZE = 3 * 1024 * 1024;    // 設定上傳檔案最大為 3M
   final String[] allowedExt = new String[] { "jpg", "jpeg", "gif", "txt",
            "doc", "docx", "mp3", "wma", "m4a" };   // 允許上傳的檔案格式的列表
   response.setContentType("text/html");
   response.setCharacterEncoding("UTF-8");   // 設定字元編碼為UTF-8, 這樣支援漢字顯示
   // 執行個體化一個硬碟檔案工廠,用來配置上傳組件ServletFileUpload
   DiskFileItemFactory dfif = new DiskFileItemFactory();
   dfif.setSizeThreshold(4096);    // 設定上傳檔案時用於臨時存放檔案的記憶體大小,這裡是4K.多於的部分將臨時存在硬碟
   dfif.setRepository(new File(appRealPath + "ImagesUploadTemp//"));
             // 設定存放臨時檔案的目錄,web根目錄下的ImagesUploadTemp目錄
   // 用以上工廠執行個體化上傳組件
   ServletFileUpload sfu = new ServletFileUpload(dfif);
  
   sfu.setSizeMax(MAX_SIZE);    // 設定最大上傳尺寸
   PrintWriter out = response.getWriter();
  
   // 從request得到 所有 上傳域的列表  
   List fileList = null;
   try {
    fileList = sfu.parseRequest(request);
   } catch (FileUploadException e) {// 處理檔案尺寸過大異常
    if (e instanceof SizeLimitExceededException) {
     out.println("檔案尺寸超過規定大小:" + MAX_SIZE + "位元組<p />");
     out.println("<a href=/" " + request.getContextPath() + "/fileUpload.jsp" + " /" target=/"_top/">返回</a>");
     return;
    }
    e.printStackTrace();
   }
   // 沒有檔案上傳
   if (fileList == null || fileList.size() == 0) {
    out.println("請選擇上傳檔案<p />");
    out.println("<a href=/" " + request.getContextPath() + "/fileUpload.jsp" + " /" target=/"_top/">返回</a>");
    return;
   }
   // 得到所有上傳的檔案
   Iterator fileItr = fileList.iterator();
   // 迴圈處理所有檔案
   while (fileItr.hasNext()) {
    FileItem fileItem = null;
    String path = null;
    long size = 0;
    // 得到當前檔案
    fileItem = (FileItem) fileItr.next();
    // 忽略簡單form欄位而不是上傳域的檔案域(<input type="text" />等)
    if (fileItem == null || fileItem.isFormField()) {
     continue;
    }
    // 得到檔案的完整路徑
    path = fileItem.getName();
    // 得到檔案的大小
    size = fileItem.getSize();
    if ("".equals(path) || size == 0) {
     out.println("請選擇上傳檔案<p />");
     out.println("<a href=/" " + request.getContextPath() + "/fileUpload.jsp" + " /" target=/"_top/">返回</a>");
     return;
    }
    // 得到去除路徑的檔案名稱
    String t_name = path.substring(path.lastIndexOf("//") + 1);
    // 得到檔案的副檔名(無副檔名時將得到全名)
    String t_ext = t_name.substring(t_name.lastIndexOf(".") + 1);
    // 拒絕接受規定檔案格式之外的檔案類型
    int allowFlag = 0;
    int allowedExtCount = allowedExt.length;
    for (; allowFlag < allowedExtCount; allowFlag++) {
     if (allowedExt[allowFlag].equals(t_ext))
      break;
    }
    if (allowFlag == allowedExtCount) {
     out.println("請上傳以下類型的檔案<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();
    // 根據系統時間產生上傳後儲存的檔案名稱
    String prefix = String.valueOf(now);
    // 儲存的最終檔案完整路徑,儲存在web根目錄下的ImagesUploaded目錄下
    String u_name = appRealPath + "ImagesUploaded//"
      + prefix + "." + t_ext;
    try {
     // 儲存檔案
     fileItem.write(new File(u_name));
     out.println("檔案上傳成功. 已儲存為: " + prefix + "." + t_ext
       + " &nbsp;&nbsp;檔案大小: " + size + "位元組<p />");
     out.println("<a href=/" " + request.getContextPath() + "/fileUpload.jsp" + " /" target=/"_top/">繼續上傳</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>

記得在上傳的form裡指明enctype="multipart/form-data"，具體的讀一下FileUpload.java就清楚了。