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]+"&nbsp;&nbsp;&nbsp;"); 
               }
               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  
                       + " &nbsp;&nbsp;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();  
            }  

      }  
 
   }

}