jquery异步上传文件

一、创建input元素

<input type="file" id="fileToUpload" name="fileToUpload" value="浏览"/>

二、导入jquery.js和ajaxfileupload.js文件

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 formvar 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 attributesjQuery(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" ) {        if(data.indexOf('<pre') != -1) {                //此段代码时为了兼容火狐和chrome浏览器var newDiv = jQuery(document.createElement("div"));                newDiv.html(data);                data = $("pre:first", newDiv).html(); }              eval( "data = " + data );        }        // evaluate scripts within html        if ( type == "html" )            jQuery("<div>").html(data).evalScripts();        return data;    }});

注意：在ajaxfileupload中会用到jquery的handleError函数，但是此函数在1.4.2之后不存在了，所有如果用到更高的

版本需要复制进去

三、写调用代码

function uploadImage() {$.ajaxFileUpload({url: 'photo/upload',//需要链接到服务器地址secureuri:false,fileElementId: 'fileToUpload',//文件选择框的id属性dataType:'json',//服务器返回的格式，可以是jsonsuccess: function (data){if (data['result'] == 1) {}},error: function(data){}});}

四、写后台处理代码：

List items = super.getUploadFileItems(req);//使用fileupolad组件获取request中的参数HashMap<String, String> params = super.getUploadParams(items);Iterator iter = items.iterator();FileItem fileItem = null;while (iter.hasNext()) {FileItem item = (FileItem) iter.next();if (!item.isFormField()) {fileItem = item;break;}}byte[] imageContent = null;String suffix = null;if (fileItem != null) {imageContent = IOTools.readContent(fileItem.getInputStream(), 4096);suffix = fileItem.getContentType();}

注意：

（1）如果服务端想返回json格式，一定不能加上response.setContentType("application/json");

 否则IE和opera会解析成文件下载，或者写成response.setContentType("text/html");

结合strut2是result节点中也要设置contentType，否则浏览器总是提示将返回的JSON结果另存为文件，不会交给ajaxfileupload处理。

这是因为struts2 JSON Plugin默认的contentType为application/json，而ajaxfileupload则要求为text/html。

（2）返回url赋值给img的src时，记得加上时间戳或者保证url不重复，否则会被浏览器缓存，导致无法实时看到图片