最近在做一個專案需要實現非同步上傳圖片，在網上找了很多資料後，採用了ajaxfileupload可以實現，以下是核心程式碼：

jsp:

<!-- 上傳視窗 -->   
    <div id="uploadPicWindow" class="easyui-window" title="上傳圖片"  style="width:420px;height:220px;padding:20px;background:#fafafa;" data-options="iconCls:'icon-save',closable:true, collapsible:true,minimizable:true,maximizable:true">  
        <form id="picForm" action="" method="post">  
            <div style="margin-bottom:20px">  
                圖片名稱:  
                <input type="text" name="name" id="picName" class="easyui-textbox" style="width:80%" data-options="required:true,validType:'stringCheck'"/>  
            </div>  
            <br/>  
            <div style="margin-bottom:20px">  
                選擇圖片:  
                <input type="file" name="file" id="file" data-options="prompt:'Choose a file...'" style="width:80%"/>  
            </div>  
            <div id="picTip"></div>  
            <div id="formWindowfooterPic1" style="padding:5px;text-align:right;">   
                <a href="#" onclick="submitPic();" class="easyui-linkbutton" data-options="iconCls:'icon-save'">提交</a>  
            </div>  
        </form>  
    </div>  

js:

//新建或編輯 儲存提交  
function submitPic(){  
    if(!$("#picForm").form('validate')){  
        return false;  
    }  
    var projectId = $("#projectId").val();  
    var name=$("#picName").val();  
    var type="1";//展示圖片  
    var f = $("#file").val();  
    if(f==null||f==""){  
        $("#picTip").html("<span style='color:Red'>錯誤提示:上傳檔案不能為空,請重新選擇檔案</span>");  
        return false;  
      }else{  
       var extname = f.substring(f.lastIndexOf(".")+1,f.length);  
       extname = extname.toLowerCase();//處理了大小寫  
       if(extname!= "jpeg"&&extname!= "jpg"&&extname!= "gif"&&extname!= "png"){  
         $("#picTip").html("<span style='color:Red'>錯誤提示:格式不正確,支援的圖片格式為：JPEG、GIF、PNG！</span>");  
         return false;  
        }  
      }  
     var file = document.getElementById("file").files;    
     var size = file[0].size;  
     if(size>2097152){  
          $("#picTip").html("<span style='color:Red'>錯誤提示:所選擇的圖片太大，圖片大小最多支援2M!</span>");   
          return false;  
      }  
    ajaxFileUploadPic(projectId,name,type);  
}  
  
function ajaxFileUploadPic(projectId,name,type) {  
    $.ajaxFileUpload({  
        url : '${ctx}/projectPic/saveorupdate.jhtml?projectId='+projectId+'&name='+name+'&type='+type, //用於檔案上傳的伺服器端請求地址  
        secureuri : false, //一般設定為false  
        fileElementId : 'file', //檔案上傳空間的id屬性  <input type="file" id="file" name="file" />  
        type : 'post',  
        dataType : 'json', //返回值型別 一般設定為json  
        success : function(data, status) //伺服器成功響應處理函式  
        {  
             $("#picList").datagrid('reload');  
             $('#uploadPicWindow').window('close');  
            // alert(data.msg);  
        },  
        error : function(data, status, e)//伺服器響應失敗處理函式  
        {  
             $("#picList").datagrid('reload');  
             $('#uploadPicWindow').window('close');  
            // alert(data.msg);  
        }  
    });  
    return false;  
}  

jQuery.extend({  
      
    createUploadIframe: function(id, uri)  
    {  
            //create frame  
            var frameId = 'jUploadFrame' + id;  
            var iframeHtml = '<iframe id="' + frameId + '" name="' + frameId + '" style="position:absolute; top:-9999px; left:-9999px"';  
            if(window.ActiveXObject)  
            {  
                if(typeof uri== 'boolean'){  
                    iframeHtml += ' src="' + 'javascript:false' + '"';  
  
                }  
                else if(typeof uri== 'string'){  
                    iframeHtml += ' src="' + uri + '"';  
  
                }     
            }  
            iframeHtml += ' />';  
            jQuery(iframeHtml).appendTo(document.body);  
  
            return jQuery('#' + frameId).get(0);              
    },  
    createUploadForm: function(id, fileElementId, data)  
    {  
        //create form     
        var formId = 'jUploadForm' + id;  
        var fileId = 'jUploadFile' + id;  
        var form = jQuery('<form  action="" method="POST" name="' + formId + '" id="' + formId + '" enctype="multipart/form-data"></form>');      
        if(data)  
        {  
            for(var i in data)  
            {  
                jQuery('<input type="hidden" name="' + i + '" value="' + data[i] + '" />').appendTo(form);  
            }             
        }         
        var oldElement = jQuery('#' + fileElementId);  
        var newElement = jQuery(oldElement).clone();  
        jQuery(oldElement).attr('id', fileId);  
        jQuery(oldElement).before(newElement);  
        jQuery(oldElement).appendTo(form);  
  
  
          
        //set attributes  
        jQuery(form).css('position', 'absolute');  
        jQuery(form).css('top', '-1200px');  
        jQuery(form).css('left', '-1200px');  
        jQuery(form).appendTo('body');        
        return form;  
    },  
  
    ajaxFileUpload: function(s) {  
        // TODO introduce global settings, allowing the client to modify them for all requests, not only timeout          
        s = jQuery.extend({}, jQuery.ajaxSettings, s);  
        var id = new Date().getTime()          
        var form = jQuery.createUploadForm(id, s.fileElementId, (typeof(s.data)=='undefined'?false:s.data));  
        var io = jQuery.createUploadIframe(id, s.secureuri);  
        var frameId = 'jUploadFrame' + id;  
        var formId = 'jUploadForm' + id;          
        // Watch for a new set of requests  
        if ( s.global && ! jQuery.active++ )  
        {  
            jQuery.event.trigger( "ajaxStart" );  
        }              
        var requestDone = false;  
        // Create the request object  
        var xml = {}     
        if ( s.global )  
            jQuery.event.trigger("ajaxSend", [xml, s]);  
        // Wait for a response to come back  
        var uploadCallback = function(isTimeout)  
        {             
            var io = document.getElementById(frameId);  
            try   
            {                 
                if(io.contentWindow)  
                {  
                     xml.responseText = io.contentWindow.document.body?io.contentWindow.document.body.innerHTML:null;  
                     xml.responseXML = io.contentWindow.document.XMLDocument?io.contentWindow.document.XMLDocument:io.contentWindow.document;  
                       
                }else if(io.contentDocument)  
                {  
                     xml.responseText = io.contentDocument.document.body?io.contentDocument.document.body.innerHTML:null;  
                    xml.responseXML = io.contentDocument.document.XMLDocument?io.contentDocument.document.XMLDocument:io.contentDocument.document;  
                }                         
            }catch(e)  
            {  
                jQuery.handleError(s, xml, null, e);  
            }  
            if ( xml || isTimeout == "timeout")   
            {                 
                requestDone = true;  
                var status;  
                try {  
                    status = isTimeout != "timeout" ? "success" : "error";  
                    // Make sure that the request was successful or notmodified  
                    if ( status != "error" )  
                    {  
                        // process the data (runs the xml through httpData regardless of callback)  
                        var data = jQuery.uploadHttpData( xml, s.dataType );      
                        // If a local callback was specified, fire it and pass it the data  
                        if ( s.success )  
                            s.success( data, status );  
      
                        // Fire the global callback  
                        if( s.global )  
                            jQuery.event.trigger( "ajaxSuccess", [xml, s] );  
                    } else  
                        jQuery.handleError(s, xml, status);  
                } catch(e)   
                {  
                    status = "error";  
                    jQuery.handleError(s, xml, status, e);  
                }  
  
                // The request was completed  
                if( s.global )  
                    jQuery.event.trigger( "ajaxComplete", [xml, s] );  
  
                // Handle the global AJAX counter  
                if ( s.global && ! --jQuery.active )  
                    jQuery.event.trigger( "ajaxStop" );  
  
                // Process result  
                if ( s.complete )  
                    s.complete(xml, status);  
  
                jQuery(io).unbind()  
  
                setTimeout(function()  
                                    {   try   
                                        {  
                                            jQuery(io).remove();  
                                            jQuery(form).remove();    
                                              
                                        } catch(e)   
                                        {  
                                            jQuery.handleError(s, xml, null, e);  
                                        }                                     
  
                                    }, 100)  
  
                xml = null  
  
            }  
        }  
        // Timeout checker  
        if ( s.timeout > 0 )   
        {  
            setTimeout(function(){  
                // Check to see if the request is still happening  
                if( !requestDone ) uploadCallback( "timeout" );  
            }, s.timeout);  
        }  
        try   
        {  
  
            var form = jQuery('#' + formId);  
            jQuery(form).attr('action', s.url);  
            jQuery(form).attr('method', 'POST');  
            jQuery(form).attr('target', frameId);  
            if(form.encoding)  
            {  
                jQuery(form).attr('encoding', 'multipart/form-data');                 
            }  
            else  
            {     
                jQuery(form).attr('enctype', 'multipart/form-data');              
            }             
            jQuery(form).submit();  
  
        } catch(e)   
        {             
            jQuery.handleError(s, xml, null, e);  
        }  
          
        jQuery('#' + frameId).load(uploadCallback   );  
        return {abort: function () {}};   
  
    },  
  
    uploadHttpData: function( r, type ) {  
        var data = !type;  
        data = type == "xml" || data ? r.responseXML : r.responseText;  
        // If the type is "script", eval it in global context  
        if ( type == "script" )  
            jQuery.globalEval( data );  
        // Get the JavaScript object, if JSON is used.  
        if ( type == "json" )  
            eval( "data = " + data );  
        // evaluate scripts within html  
        if ( type == "html" )  
            jQuery("<div>").html(data).evalScripts();  
  
        return data;  
    },  
    handleError: function( s, xhr, status, e )      {  
        // If a local callback was specified, fire it  
                if ( s.error ) {  
                    s.error.call( s.context || s, xhr, status, e );  
                }  
  
                // Fire the global callback  
                if ( s.global ) {  
                    (s.context ? jQuery(s.context) : jQuery.event).trigger( "ajaxError", [xhr, s, e] );  
                }  
    }  
   
})  

注：如果出現

<strong><span style="color: rgb(255, 0, 0);">jQuery.handleError is not a function </span></strong>

<span style="color: rgb(51, 51, 51);">原因是，經測試handlerError只在jquery-1.4.2之前的版本中存在，jquery-1.6 和1.7中都沒有這個函式了，因此在1.4.2中將這個函式複製到了ajaxFileUpload.js中，問題解決
handleError: function( s, xhr, status, e ) 		{
// If a local callback was specified, fire it
		if ( s.error ) {
			s.error.call( s.context || s, xhr, status, e );
		}

		// Fire the global callback
		if ( s.global ) {
			(s.context ? jQuery(s.context) : jQuery.event).trigger( "ajaxError", [xhr, s, e] );
		}
	},
問題2：一直得到error ，無法執行指定的success方法。通過追蹤ajaxFileUpload的執行過程發現，在呼叫它自身的uploadHttpData函式時，當執行if（type=="json")    eval("data = "+data);
會丟擲異常，導致在處理異常的時候將status = "error" 因此一直執行error方法。
上網查詢，得知eval函式是用來執行一段js程式碼，而並不是如我所想的反解json串
eval("data = "+data);的意思是 將data 賦值給 data引數 ，但是當我返回給頁面的是一個簡單的字串，比如"OK" ，時，這樣寫就丟擲異常。最後改為 eval("data = \" "+data+" \" ");即將返回的資料用雙引號引起來當作字串，然後賦給 data 。終於成功了。。。
</span>

       @RequestMapping(value = "/saveorupdate.jhtml")  
@ResponseBody  
public synchronized String saveOrUpdate(HttpServletRequest request) throws IOException {  
    DynamicParams params = new DynamicParams(request);  
    String projectId = request.getParameter("projectId");  
    String name = request.getParameter("name");  
    String type = request.getParameter("type");  
    params.put("projectId", projectId);  
    params.put("name", name);  
    params.put("type", type);  
  
    MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;  
    MultipartFile file = null;  
    if("1".equals(type)){  
        file = multipartRequest.getFile("file");// 獲取上傳檔名  
    }else{  
        file = multipartRequest.getFile("attachFile");// 獲取上傳檔名  
    }  
    ProjectPic projectPic = params.convertToEntity(ProjectPic.class);         
    projectPicManager.save(projectPic, file.getInputStream());  
    return successMsg();  
}