掌控上传进度的AJAX Upload

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Ajax DWR Bean prototype JavaScript

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》一文。虽然文中完成Upload工作的是Common-FileUpload组件，但在其代码中没有1.2版本所提供的Listener功能，这就对检测文件上传情况造成了困难...

掌控上传进度的AJAX Upload

作者：cleverpig

AJAX——最酷的“冲浪板”

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;