package cn.com.seegoo.xm.front.servlets;

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.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import cn.com.seegoo.servletrest.servlets.BaseServlet;

public class PhotoUpServlet extends BaseServlet{
 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 PhotoUpServlet() {
        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("/")
                + "upload"));// 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();
            }

        }
    }

}

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:'PhotoUpServlet',//用于文件上传的服务器端请求地址
                secureuri:false,//一般设置为false
                fileElementId:'fileField',//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;

    }

界面：

<body>

 <img src="images/loading.gif" id="loading" style="display: none;">

   <span style="color: red;" id="myspan"></span><br/>

        <input type="file" id="fileField" name="file" />
        <br />
        <input type="button" value="上传" onclick="return ajaxFileUpload();">
</body>

web.xml:

<servlet>
        <servlet-name>PhotoUpServlet</servlet-name>
        <servlet-class>cn.com.seegoo.xm.front.servlets.PhotoUpServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>PhotoUpServlet</servlet-name>
        <url-pattern>/PhotoUpServlet</url-pattern>
    </servlet-mapping>