使用commons.fileupload包实现的大文件上传功能

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 {

/**
* Constructor of the object.
*/
public FileUploadServlet() {
   super();
}

/**
* Destruction of the servlet. <br>
*/
public void destroy() {
   super.destroy(); // Just puts "destroy" string in log
   // Put your code here
}

/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {

   doPost(request, response);
}

/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {

   final long MAX_SIZE = 1024 * 1024 * 1024;// 设置上传文件最大为 1G
   // 允许上传的文件格式的列表
   final String[] allowedExt = new String[] { "txt" };

   response.setContentType("text/html; charset=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();
   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(request.getRealPath("upload/temp/")));// 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);
   // 设置最大上传尺寸
   sfu.setSizeMax(MAX_SIZE);

   PrintWriter out = response.getWriter();
   // 从request得到 所有 上传域的列表
   List fileList = null;
   String fullpath="";
   String filename="";
   String savepath="";
   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=\"<%=path %>/<%=request.getAttribute(\"returnjsp\") %>\" class=\"soft2\">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=\"<%=path %>/<%=request.getAttribute(\"returnjsp\") %>\" class=\"soft2\">返回</a>");
    return;
   }
   // 得到所有上传的文件
   Iterator fileItr = fileList.iterator();
   int i = 0;
   // 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();
    i++;
    // 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=\"<%=path %>/<%=request.getAttribute(\"returnjsp\") %>\" class=\"soft2\">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=\"<%=path %>/<%=request.getAttribute(\"returnjsp\") %>\" class=\"soft2\">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("upload/")+"/" + t_name;

    //保存文件之前，查看目录下是否有重名文件，如果有，删除
    File existfile = new File(u_name);
    if(existfile.exists()){
     existfile.delete();
     System.out.println(" file:"+u_name+" is deleted.");
    }
    //System.exit(0);
  
    try {
     // 保存文件
     fileItem.write(new File(u_name));
     out.println("<a href=\"<%=path %>/<%=request.getAttribute(\"returnjsp\") %>\" class=\"soft2\">返回</a>");
    } catch (Exception e) {
     e.printStackTrace();
    }
    fullpath = u_name;
    filename = t_name;
    savepath = request.getRealPath("upload/");
   }
 
   request.setAttribute("fullpath", fullpath);
   request.setAttribute("filename", filename);
   request.setAttribute("savepath", savepath);
 
   System.out.println("servlet,fullpath:" + fullpath);
   System.out.println("servlet,filename:" + filename);
   System.out.println("servlet,savepath:" + savepath);

   System.out.println("finish upload file servlet method...");
   response.sendRedirect(request.getContextPath()+"/upload/uploadok.jsp?fullpath="+fullpath+"&filename="+filename+"&savepath="+savepath);
 
}

/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
   // Put your code here
}

}