掌控上传进度的AJAX Upload

动机：

        2006年底Google了一下AJAX Upload实现，结果没有发现很完整的Java实现。硕果仅存的就是TELIO公司的Pierre-Alexandre发表的《AJAX Upload progress monitor for Commons-FileUpload Example》文中提供的ajax-upload-1.0.war。

        虽然上文中完成Upload工作的是Apache的Common-FileUpload组件，但在其代码中所使用的FileUpload1.1版本并没有1.2版本所提供的上传处理Listener功能，这就对检测文件上传情况造成了困难。我想正是这个原因致使Pierre-Alexandre使用了DWR+MonitoredDiskFileItem、MonitoredDiskFileItemFactory类（分别继承DiskFileItem、DiskFileItemFactory）的方式：前者负责在web客户端进行Remote Call；后者在进行文件数据读取时统计数据总量、读取数据量、处理文件总数，并保存于Session中，以供web客户端通过DWR远程调用UploadMonitor类的getUploadInfo方法进行轮询（Poll）。

        从本人观点出发，Pierre-Alexandre实现的不足之处：
        1.没有用户取消上传功能；
        2.完全的DWR实现，没有使用Prototype，对于不会使用DWR的开发者来讲有一定的知识局限性，而且由于DWR的个性而造成不便将此实现集成到项目中。



Prototype+Servlet的实现：



Prototype+Servlet的Example



        所以出于研究Prototype之目的，本人经过仔细思考，尝试实现了一个Prototype+Servlet的简单Example。其工作流程很简单：
1.在Form提交上传文件Field的同时，使用AJAX周期性地从Servlet轮询上传状态信息；
2.然后，根据此信息更新进度条和相关文字，及时反映文件传输状态；
3.如果用户取消上传操作，则进行相应的现场清理工作：删除已经上传的文件，在Form提交页面中显示相关信息；
4.如果上传完毕，在Form提交页面中显示已经上传的文件内容（或链接），也可以与一些AJAX SlideShow应用结合在一起。

服务器端代码：

        Bean序列化/反序列化工作：XmlUnSerializer这个类虽然不能够通吃任何模样的Bean，但应付一般的Bean、具有Collection类型属性的Bean和Bean List来讲还是够用的。
        {XmlUnSerializer类的核心方法serializeBean和serializeBeanList}:

        /**         * 将bean系列化为UTF-8编码的xml         * @param beanObj         * @return         * @throws IOException         */        public static String serializeBean(Object beanObj) throws IOException{        …        }        /**         * 将bean列表序列化为UTF-8编码的xml         * @param beanObj         * @return         * @throws IOException         */        public static String serializeBeanList(Object beanListObj) throws IOException{        …        }


        文件上传状态Bean：使用FileUploadStatus这个类记录文件上传状态，并将其作为服务器端与web客户端之间通信的媒介物：通过对这个类对象进行XML序列化作为服务器回应发送给web客户端，web客户端使用JavaScript对其进行反序列化处理获得JavaScript版本的文件上传状态对象。
        {FileUploadStatus的属性}:

        //上传总量        private long uploadTotalSize=0;        //读取上传总量        private long readTotalSize=0;        //当前上传文件号        private int currentUploadFileNum=0;        //成功读取上传文件数        private int successUploadFileCount=0;        //状态        private String status="";        //处理起始时间        private long processStartTime=0l;        //处理终止时间        private long processEndTime=0l;        //处理执行时间        private long processRunningTime=0l;        //上传文件URL列表        private List uploadFileUrlList=new ArrayList();        //取消上传        private boolean cancel=false;        //上传base目录        private String baseDir="";


        文件上传状态监视工作：使用Common-FileUpload 1.2版本（20070103）。此版本与1.1版的区别在于提供了能够监视文件上传情况的ProcessListener接口，使开发者通过FileUploadBase类对象的setProcessListener方法植入自己的Listener，而且实现这个Listener很简单。
        {FileUploadListener主要方法update}：

/*** 更新状态* @param pBytesRead 读取字节总数* @param pContentLength 数据总长度* @param pItems 当前正在被读取的field号*/public void update(long pBytesRead, long pContentLength, int pItems){FileUploadStatus fuploadStatus=BackGroundService.takeOutFileUploadStatusBean(this.session);logger.debug("当前正在处理第" + pItems+"个文件");fuploadStatus.setUploadTotalSize(pContentLength);    //读取完成if (pContentLength == -1) {   logger.debug("读取完成:读取了 " + pBytesRead + " bytes.");   fuploadStatus.setStatus("完成对" + pItems+"个文件的读取:读取了 " + pBytesRead + " bytes.");   fuploadStatus.setReadTotalSize(pBytesRead);   fuploadStatus.setSuccessUploadFileCount(pItems);   fuploadStatus.setProcessEndTime(System.currentTimeMillis());   fuploadStatus.setProcessRunningTime(fuploadStatus.getProcessEndTime());            //读取中    } else {     logger.debug("读取进行中:已经读取了 " + pBytesRead + " / " + pContentLength+ " bytes.");     fuploadStatus.setStatus("当前正在处理第" + pItems+"个文件:已经读取了 " + pBytesRead + " / " + pContentLength+ " bytes.");     fuploadStatus.setReadTotalSize(pBytesRead);     fuploadStatus.setCurrentUploadFileNum(pItems);     fuploadStatus.setProcessRunningTime(System.currentTimeMillis());            }BackGroundService.storeFileUploadStatusBean(this.session,fuploadStatus);        } 很清楚，我也把FileUploadStatus这个Bean存取于Session中。        Servlet实现：BackGroundService这个Servlet类负责接收Form Post数据、回应状态轮询请求、处理取消文件上传的请求。尽管可以把这些功能相互分离开来（比如构造一个FileUploadManager类），但出于简单明了、便于阅读之目的，还是将它们放到Servlet中，只是由不同的方法进行分割。        {BackGroundService中的processFileUpload方法用于处理文件上传请求}：/*** 处理文件上传* @param request* @param response* @throws IOException * @throws ServletException */private void processFileUpload(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{      DiskFileItemFactory factory = new DiskFileItemFactory();      //设置内存阀值，超过后写入临时文件      factory.setSizeThreshold(10240000);      //设置临时文件存储位置      factory.setRepository(new File(request.getRealPath("/upload/temp")));      ServletFileUpload upload = new ServletFileUpload(factory);      //设置单个文件的最大上传size      upload.setFileSizeMax(10240000);      //设置整个request的最大size      upload.setSizeMax(10240000);      upload.setProgressListener(new FileUploadListener(request.getSession()));      //保存初始化后的FileUploadStatus Bean        storeFileUploadStatusBean(request.getSession(),initFileUploadStatusBean(request));                        String forwardURL="";        try {             List items = upload.parseRequest(request);             //获得返回url               for(int i=0;i<items.size();i++){                   FileItem item=(FileItem)items.get(i);                   if (item.isFormField()){                      logger.debug("form Field［"+item.getFieldName()+"］="+item.getString());                      forwardURL=item.getString();                      break;                                }                        }            //处理文件上传              for(int i=0;i<items.size();i++){                 FileItem item=(FileItem)items.get(i);                   //取消上传                 if (takeOutFileUploadStatusBean(request.getSession()).getCancel()){                     deleteUploadedFile(request);                     break;                    }                   //保存文件                 else if (!item.isFormField() && item.getName().length()>0){                         String fileName=takeOutFileName(item.getName());                         logger.debug("处理文件［"+fileName+"］:保存路径为"                         +request.getRealPath(UPLOAD_DIR)+File.separator+fileName);                         File uploadedFile =              new File(request.getRealPath(UPLOAD_DIR)+File.separator+fileName);                         item.write(uploadedFile);                         //更新上传文件列表                         FileUploadStatus fUploadStatus=takeOutFileUploadStatusBean                         (request.getSession());                         fUploadStatus.getUploadFileUrlList().add(fileName);                         storeFileUploadStatusBean(request.getSession(),fUploadStatus);                         Thread.sleep(500);                          }                 }                       } catch (FileUploadException e) {              logger.error("上传文件时发生错误:"+e.getMessage());              e.printStackTrace();              uploadExceptionHandle(request,"上传文件时发生错误:"+e.getMessage());        } catch (Exception e) {               // TODO Auto-generated catch block               logger.error("保存上传文件时发生错误:"+e.getMessage());               e.printStackTrace();               uploadExceptionHandle(request,"保存上传文件时发生错误:"+e.getMessage());         }          if (forwardURL.length()==0){             forwardURL=DEFAULT_UPLOAD_FAILURE_URL;                }        request.getRequestDispatcher(forwardURL).forward(request,response);        }        {BackGroundService中的responseFileUploadStatusPoll方法用于处理对文件上传状态的轮询请求}：/*** 回应上传状态查询* @param request* @param response* @throws IOException*/private void responseFileUploadStatusPoll(HttpServletRequest request,HttpServletResponse response) throws IOException{response.setContentType("text/xml");response.setCharacterEncoding("UTF-8");response.setHeader("Cache-Control", "no-cache");logger.debug("发送上传状态回应");response.getWriter().write(XmlUnSerializer.serializeBean(          request.getSession().getAttribute(UPLOAD_STATUS)));}        {BackGroundService中的processCancelFileUpload方法用于处理取消文件上传的请求}：/*** 处理取消文件上传* @param request* @param response* @throws IOException*/private void processCancelFileUpload(HttpServletRequest request,HttpServletResponse response) throws IOException{FileUploadStatus fUploadStatus=(FileUploadStatus)request.getSession().getAttribute(UPLOAD_STATUS);fUploadStatus.setCancel(true);request.getSession().setAttribute(UPLOAD_STATUS, fUploadStatus);responseFileUploadStatusPoll(request,response); }Web客户端代码：Prototype给开发者更多的自由选择web客户端使用了基于Prototype的AjaxWrapper类和XMLDomForAjax类，前者实现了对Ajax.Request功能的封装，而后者实现了对来自服务器的XML Response的反序列化（反序列化为JavaScript对象）。 为了避免在AjaxWrapper的回调方法中发生this被重写的问题，我使用了ClassUtils类给任何类的每个方法注册一个对类对象自身引用，详见《解开JavaScript生命的达芬奇密码》和《Prototype.AjaxRequest的调用堆栈重写问题》：        {ClassUtils类代码}：//类工具var ClassUtils=Class.create();ClassUtils.prototype={        _ClassUtilsName:'ClassUtils',        initialize:function(){        },        /**         * 给类的每个方法注册一个对类对象的自我引用         * @param reference 对类对象的引用         */        registerFuncSelfLink:function(reference){                for (var n in reference) {                var item = reference［n］;                                        if (item instanceof Function)                                 item.$ = reference;            }        }}        {将XML反序列化为JavaScript对象的XMLDomForAjax类代码}：var XMLDomForAjax=Class.create();XMLDomForAjax.prototype={        isDebug:false,        //dom节点类型常量        ELEMENT_NODE:1,        ATTRIBUTE_NODE:2,    TEXT_NODE:3,    CDATA_SECTION_NODE:4,    ENTITY_REFERENCE_NODE:5,    ENTITY_NODE:6,    PROCESSING_INSTRUCTION_NODE:7,    COMMENT_NODE:8,    DOCUMENT_NODE:9,    DOCUMENT_TYPE_NODE:10,    DOCUMENT_FRAGMENT_NODE:11,    NOTATION_NODE:12,            initialize:function(isDebug){                new ClassUtils().registerFuncSelfLink(this);                this.isDebug=isDebug;        },        /**         * 建立跨平台的dom解析器         * @param xml xml字符串         * @return dom解析器         */        createDomParser:function(xml){                // code for IE                if (window.ActiveXObject){                  var doc=new ActiveXObject("Microsoft.XMLDOM");                  doc.async="false";                  doc.loadXML(xml);                }                // code for Mozilla, Firefox, Opera, etc.                else{                  var parser=new DOMParser();                  var doc=parser.parseFromString(xml,"text/xml");                }                return doc;        },        /**         * 反向序列化xml到javascript Bean         * @param xml xml字符串         * @return javascript Bean         */        deserializedBeanFromXML:function (xml){                var funcHolder=arguments.callee.$;                var doc=funcHolder.createDomParser(xml);                // documentElement总表示文档的root                var objDomTree=doc.documentElement;                var obj=new Object();            for (var i=0; i<objDomTree.childNodes.length; i++) {                    //获得节点                    var node=objDomTree.childNodes［i］;                    //取出其中的field元素进行处理                if ((node.nodeType==funcHolder.ELEMENT_NODE) && (node.tagName == 'field')) {                        var nodeText=funcHolder.getNodeText(node);                        if (funcHolder.isDebug){           alert(node.getAttribute('name')+' type:'+node.getAttribute('type')+' text:'+nodeText);                        }                    var objFieldValue=null;                    //如果为列表                    if (node.getAttribute('type')=='java.util.List'){                            if (objFieldValue && typeof(objFieldValue)=='Array'){                                    if (nodeText.length>0){                                                        objFieldValue［objFieldValue.length］=nodeText;                                                }                                        }                                        else{                                                objFieldValue=new Array();                                        }                                }                                else if (node.getAttribute('type')=='long'                                         || node.getAttribute('type')=='java.lang.Long'                                        || node.getAttribute('type')=='int'                                        || node.getAttribute('type')=='java.lang.Integer'){                                                                                objFieldValue=parseInt(nodeText);                                }                                else if (node.getAttribute('type')=='double'                                         || node.getAttribute('type')=='float'                                        || node.getAttribute('type')=='java.lang.Double'                                        || node.getAttribute('type')=='java.lang.Float'){                                                                                objFieldValue=parseFloat(nodeText);                                }                                else if (node.getAttribute('type')=='java.lang.String'){                                        objFieldValue=nodeText;                                }                                else{                                        objFieldValue=nodeText;                                }                                //赋值给对象                                obj［node.getAttribute('name')］=objFieldValue;                                if (funcHolder.isDebug){                                        alert(eval('obj.'+node.getAttribute('name')));                                }                }                else if (node.nodeType == funcHolder.TEXT_NODE){                        if (funcHolder.isDebug){                                //alert('TEXT_NODE');                        }                                        }                else if (node.nodeType == funcHolder.CDATA_SECTION_NODE){                        if (funcHolder.isDebug){                                //alert('CDATA_SECTION_NODE');                        }                }            }            return obj;        },        /**         * 获得dom节点的text         */        getNodeText:function (node) {                var funcHolder=arguments.callee.$;            // is this a text or CDATA node?     if (node.nodeType == funcHolder.TEXT_NODE || node.nodeType == funcHolder.CDATA_SECTION_NODE) {                return node.data;            }            var i;            var returnValue = ［］;            for (i = 0; i < node.childNodes.length; i++) {                    //采用递归算法                returnValue.push(funcHolder.getNodeText(node.childNodes［i］));            }            return returnValue.join('');        }}AjaxWrapper类的主要方法putRequest和callBackHandler}：         /**         * 以get的方式向server发送request         * @param url         * @param params         * @param callBackFunction 发送成功后回调的函数或者函数名         */        putRequest:function(url,params,callBackFunction){                var funcHolder=arguments.callee.$;            var xmlHttp = new Ajax.Request(url,                        {                                method: 'get',                             parameters: params,                                 requestHeaders:［'my-header-encoding','utf-8'］,                            onFailure: function(){                                        alert('对不起，网络通讯失败，请重新刷新！');                                },                                onSuccess: function(transport){                                },                                onComplete: function(transport){                         funcHolder.callBackHandler.apply(funcHolder,［transport,callBackFunction］);                                }                        });        },        /**         * 远程调用的回调处理         * @param transport xmlhttp的transport         * @param callBackFunction 回调时call的方法，可以是函数也可以是函数名         */        callBackHandler:function(transport,callBackFunction){                var funcHolder=arguments.callee.$;                if(transport.status!=200){                        alert("获得回应失败,请求状态:"+transport.status);                }                else{                        funcHolder.xml_source=transport.responseText;                        if (funcHolder.debug_flag)                                alert('call callback function');                        if (typeof(callBackFunction)=='function'){                                if (funcHolder.debug_flag){                                        alert('invoke callbackFunc');                                }                                callBackFunction(transport.responseText);                        }                        else{                                if (funcHolder.debug_flag){                                        alert('evalFunc callbackFunc');                                }                                new execute().evalFunc(callBackFunction,transport.responseText);                        }                        if (funcHolder.debug_flag)                                alert('end callback function');                }        }        {页面中主要的JavaScript方法：refreshUploadStatus和startProcess/cancelProcess}：//刷新上传状态function refreshUploadStatus(){        var ajaxW = new AjaxWrapper(false);        ajaxW.putRequest(                './uploadStatus.action',                'uploadStatus=',                function(responseText){                        var deserialor=new XMLDomForAjax(false);                        var uploadInfo=deserialor.deserializedBeanFromXML(responseText);                        var progressPercent = Math.ceil(                                (uploadInfo.readTotalSize) / uploadInfo.uploadTotalSize * 100);                $('progressBarText').innerHTML = ' 上传处理进度: '+progressPercent+'% ［'+                        (uploadInfo.readTotalSize)+'/'+uploadInfo.uploadTotalSize + ' bytes］'+                        ' 正在处理第'+uploadInfo.currentUploadFileNum+'个文件'+                        ' 耗时: '+(uploadInfo.processRunningTime-uploadInfo.processStartTime)+' ms';                $('progressStatusText').innerHTML=' 反馈状态: '+uploadInfo.status;                $('totalProgressBarBoxContent').style.width = parseInt(progressPercent * 3.5) + 'px';           &n, bsp;    }        );}//上传处理function startProgress(){        Element.show('progressBar');    $('progressBarText').innerHTML = ' 上传处理进度: 0%';    $('progressStatusText').innerHTML=' 反馈状态:';    $('uploadButton').disabled = true;    var periodicalExe=new PeriodicalExecuter(refreshUploadStatus,2);    return true;}//取消上传处理function cancelProgress(){        $('cancelUploadButton').disabled = true;        var ajaxW = new AjaxWrapper(false);        ajaxW.putRequest(                './uploadStatus.action',                'cancelUpload=true',                //因为form的提交，这可能不会执行                function(responseText){                        var deserialor=new XMLDomForAjax(false);                        var uploadInfo=deserialor.deserializedBeanFromXML(responseText);                        $('progressStatusText').innerHTML=' 反馈状态: '+uploadInfo.status;                        if (msgInfo.cancel=='true'){                                alert('删除成功!');                                window.location.reload();                        };                }        );}运行界面：起始页面上传进行中…上传完成后的文件列表用户取消上传后显示的页面上传过程中出错（上传文件过大）页面源代码下载：AjaxUpload.zip相关链接：        AJAX Upload progress monitor for Commons-FileUpload Example        Apache Common FileUpload组件        Prototype官方网站        IBM的AJAX SlideShow应用        解开JavaScript生命的达芬奇密码        Prototype.AjaxRequest的调用堆栈重写问题感谢阅读此文        请支持cleverpig发起的