Servlet实现文件上传-----1

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();
 } public void init() throws ServletException {
  // 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 {   
       // 设置上传文件最大为 3M 
       final long MAX_SIZE = 3 * 1024 * 1024;  
        // 允许上传的文件格式的列表   
       final String[] allowedExt = new String[] {"jpg","jpeg","gif","txt","doc","docx","mp3","wma","m4a"};  
       
       response.setContentType("text/html");   
        // 设置字符编码为UTF-8, 这样支持汉字显示   
       response.setCharacterEncoding("UTF-8");   
 
       
       // 实例化一个硬盘文件工厂,用来配置上传组件ServletFileUpload   
       DiskFileItemFactory dfif = new DiskFileItemFactory();   
       // 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.setSizeThreshold(4096);   
       // 设置存放临时文件的目录,web根目录下的ImagesUploadTemp目录   
       dfif.setRepository(new File(request.getRealPath("/")+"ImagesUploadTemp"));
       
       
       // 用以上工厂实例化上传组件   
       ServletFileUpload sfu = new ServletFileUpload(dfif);   
       // 设置最大上传尺寸   
       sfu.setSizeMax(MAX_SIZE);   
       // 从request得到所有上传域的列表   
       List fileList = null;   
       PrintWriter out = response.getWriter();   
       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="upload.html" 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="upload.html" 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(客户端的存储路径)   
           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="upload.html" 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]+"   ");  
               }
               out.println("<p /><a href="upload.html" 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 = request.getRealPath("/") + "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   
                       + "   文件大小: " + size + "字节<p />");   
               out.println("<a href="upload.html" target="_top">继续上传</a>");   
          } catch (Exception e) {   
               e.printStackTrace();   
            }        }   
 
   }}