java基于servlet的文件异步上传

package com.future.zfs.util;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;@SuppressWarnings("serial")public class FileUploadServlet extends HttpServlet {  final long MAX_SIZE = 10 * 1024 * 1024;// 设置上传文件最大为 10M  // 允许上传的文件格式的列表  final String[] allowtype = new String[] {"jpg","jpeg","gif","txt","doc","docx","mp3","wma","m4a","xls"};  public FileUploadServlet() {    super();  }  public void destroy() {    super.destroy();   }  @Override  protected void service(HttpServletRequest request, HttpServletResponse response)      throws ServletException, IOException {    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();    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("/")        + "uploadtemp"));// 设置存放临时文件的目录,web根目录下的uploadtemp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;    try {      fileList = sfu.parseRequest(request);    } catch (FileUploadException e) {// 处理文件尺寸过大异常      if (e instanceof SizeLimitExceededException) {        out.println("{message:'文件尺寸超过规定大小:"+MAX_SIZE+"字节'}");        return;      }      e.printStackTrace();    }    // 没有文件上传    if (fileList == null || fileList.size() == 0) {      out.println("{message:'请选择上传文件'}");      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("{message:'请选择上传文件'}");        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 = allowtype.length;      for (; allowFlag < allowedExtCount; allowFlag++) {        if (allowtype[allowFlag].equals(t_ext))          break;      }      if (allowFlag == allowedExtCount) {        String message = "";        for (allowFlag = 0; allowFlag < allowedExtCount; allowFlag++){          message+="*." + allowtype[allowFlag]                        + " ";        }        out.println("{message:'请上传以下类型的文件"+message+"'}");        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upload目录下      String u_name = request.getRealPath("/") + "upload/"          + prefix + "." + t_ext;      //原来的文件名      path=request.getRealPath("/") + "upload/"+path;      try {        // 保存文件        fileItem.write(new File(path));        response.setStatus(200);        out.println("{message:/"文件上传成功. 已保存为: " + prefix + "." + t_ext            + " 文件大小: " + size + "字节/"}");      } catch (Exception e) {        e.printStackTrace();      }    }  }}

<servlet>    <servlet-name>fileUploadServlet</servlet-name>    <servlet-class>com.future.zfs.util.FileUploadServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>fileUploadServlet</servlet-name>    <url-pattern>/fileUploadServlet</url-pattern>  </servlet-mapping>

<%@ page language="java" contentType="text/html; charset=UTF-8"  pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html>  <head>    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">    <title>Insert title here</title>    <script type="text/javascript" src="js/jquery.js"></script>    <script type="text/javascript" src="js/ajaxfileupload.js"></script>    <script type="text/javascript">  function ajaxFileUpload()  {        $("#loading")    .ajaxStart(function(){      $(this).show();    })//开始上传文件时显示一个图片    .ajaxComplete(function(){      $(this).hide();    });//文件上传完成将图片隐藏起来        $.ajaxFileUpload    (      {        url:'fileUploadServlet',//用于文件上传的服务器端请求地址        secureuri:false,//一般设置为false        fileElementId:'file',//文件上传空间的id属性 <input type="file" id="file" name="file" />        dataType: 'json',//返回值类型 一般设置为json        success: function (data, status) //服务器成功响应处理函数        {          //alert(data.message);//从服务器返回的json中取出message中的数据,其中message为在struts2中定义的成员变量          $('#myspan').html(data.message);          if(typeof(data.error) != 'undefined')          {            if(data.error != '')            {              //alert(data.error);              $('#myspan').html(data.message);            }else            {              //alert(data.message);              $('#myspan').html(data.message);            }          }        },        error: function (data, status, e)//服务器响应失败处理函数        {          //alert(e);          $('#myspan').html(e);        }      }    )        return false;  }  </script>  </head>  <body>    <img src="images/loading.gif" id="loading" style="display: none;">    <span style="color: red;" id="myspan"></span><br/>    <input type="file" id="file" name="file" />    <br />    <input type="button" value="上传" onclick="return ajaxFileUpload();">    <a href="fileDownLoadServlet?filename=通讯录.xls">哈哈，测试文件下载</a>  </body></html>