本文实例为大家分享了JFinal使用ajaxfileupload实现图片上传预览的具体代码，供大家参考，具体内容如下

1.前端jsp页面核心代码

<script type="text/javascript" src="<%=request.getContextPath() %>/js/jquery.min.js"></script><script type="text/javascript" src="<%=request.getContextPath() %>/media/ajaxupload/ajaxfileupload.js"></script><input type="file" class="upload" name="file" id="upfile" onchange="ajaxFileUpload('upfile')"/><!--用于预览图片--> <img src="<c:if test="${banner.img!=null}"><%=request.getContextPath() %>/media/file/${banner.img}</c:if>" style="width:300px;height:100px;" id="imgsrc"/><!--存放图片路径,提交页面时传给后台的值--><input id='imgurl' type='hidden' name="imgurl" style="height:30px;width:100%" value='${banner.img}'/>function ajaxFileUpload(fileEid, paramdata){ if(typeof(paramdata)=='undefined') paramdata = {}; var $file=$('#'+fileEid).val(); if($file=='') {alert("请先选择对应的上传文件，谢谢"); return;} $.ajaxFileUpload({ url:'<%=request.getContextPath()%>/banner/uploadpic', secureuri:false, fileElementId:fileEid, dataType: 'text', data:paramdata, success: function (result){ var result = result.substring(result.indexOf("{"),result.indexOf("}")+1); result = eval("("+result+")"); if(result.t==1){ $("#imgsrc").attr("src","<%=request.getContextPath() %>/media/file/"+result.msg); $("#imgurl").val(result.msg); }else{ alert("上传失败"); } } });}

2.后台核心代码

public void uploadpic(){ UploadFile upfile = getFile();//JFinal规定getFile()必须最先执行 File file = upfile.getFile(); String filename = file.getName(); String delfilename = filename; if(filename!=null && !filename.equals("")){ filename = new SimpleDateFormat("yyyyMMddkkmmss").format(new Date())+filename; /** * 新保存的位置 */ String path = getRequest().getSession().getServletContext() .getRealPath("/"); String newPath = "/media/file/";//自定义目录 用于存放图片 /** * 没有则新建目录 */ File floder = new File(path + newPath); if (!floder.exists()) { floder.mkdirs(); } /** * 保存新文件 */ FileInputStream fis = null; FileOutputStream fos = null; try{ File savePath = new File(path + newPath + filename); if(!savePath.isDirectory()) savePath.createNewFile(); fis = new FileInputStream(file); fos = new FileOutputStream(savePath); byte[] bt = new byte[300]; while (fis.read(bt, 0, 300) != -1) { fos.write(bt, 0, 300); } }catch(Exception e){ e.printStackTrace(); }finally{ try{ if(null!=fis) fis.close(); if(null!=fos) fos.close(); }catch(Exception e){ e.printStackTrace(); } } /** * 删除原图片，JFinal默认上传文件路径为 /upload（自动创建） */ File delFile = new File(path+"/upload/"+delfilename); if(delFile.exists()){ delFile.delete(); } setAttr("msg",filename); setAttr("t",1); }else{ setAttr("t",0); } renderJson();}

附：ajaxfileupload.js代码

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; }})

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。