一、
通过iframe来实现无刷新的的文件上传，其实是有刷新的，只是在iframe里面隐藏了而已
简单的原理说明：
<form id="form1" method="post" action="upload.do" enctype="multipart/form-data" target="uploadframe" >
<input type="file" id="upload" name="文件上传" />
</form>
<iframe id="uploadframe" name="result_frame" style="visibility:hidden;"></iframe>
form里面的target要与iframe里面的id的值相等，指示是form相应了post事件，也就是post时间相应的时候刷新的是iframe而不是整个页面。
二、
利用jQuery的插件AjaxFileUpload 可以简单地实现这个异步的上传的效果 插件地址： http://www.phpletter.com/Our-Projects/AjaxFileUpload/
<script type="text/javascript" language="javascript" src="js/jquery.js"></script>
<script type="text/javascript" language="javascript" src="js/ajaxfileupload.js"></script>
代码
function ajaxFileUpload()
{
$("#loading")
.ajaxStart(function(){
$(this).show();
})
.ajaxComplete(function(){
$(this).hide();
});
$.ajaxFileUpload
(
{
url:'Upload.ashx',
secureuri:false,
fileElementId:'fileToUpload',
dataType: 'json',
success: function (data, status)
{
if(typeof(data.error) != 'undefined')
{
if(data.error != '')
{
alert(data.error);
}else
{
alert(data.msg);
}
}
},
error: function (data, status, e)
{
alert(e);
}
}
)
return false;
}
<input id="fileToUpload" type="file" size="45" name="fileToUpload">
<input type="button" id="buttonUpload" onclick="return ajaxFileUpload();">
上传</input>
Upload.ashx
代码
if (Request.Files.Count > 0)
{
HttpPostedFile file = Request.Files[0];
string msg = "";
string error = "";
if (file.ContentLength == 0)
error = "文件长度为0";
else
{
file.SaveAs(Server.MapPath("file") + "\\" + Path.GetFileName(file.FileName));
msg = "上传成功";
}
string result = "{ error:'" + error + "', msg:'" + msg + "'}";
Response.Write(result);
Response.End();
}
PS:ajaxfileupload.js代码
代码
jQuery.extend({
createUploadIframe: function(id, uri)
{
//create frame
var frameId = 'jUploadFrame' + id;
if(window.ActiveXObject) {
var io = document.createElement('<iframe id="' + frameId + '" name="' + frameId + '" />');
if(typeof uri== 'boolean'){
io.src = 'javascript:false';
}
else if(typeof uri== 'string'){
io.src = uri;
}
}
else {
var io = document.createElement('iframe');
io.id = frameId;
io.name = frameId;
}
io.style.position = 'absolute';
io.style.top = '-1000px';
io.style.left = '-1000px';
document.body.appendChild(io);
return io
},
createUploadForm: function(id, fileElementId)
{
//create form
var formId = 'jUploadForm' + id;
var fileId = 'jUploadFile' + id;
var form = $('<form action="" method="POST" name="' + formId + '" id="' + formId + '" enctype="multipart/form-data"></form>');
var oldElement = $('#' + fileElementId);
var newElement = $(oldElement).clone();
$(oldElement).attr('id', fileId);
$(oldElement).before(newElement);
$(oldElement).appendTo(form);
//set attributes
$(form).css('position', 'absolute');
$(form).css('top', '-1200px');
$(form).css('left', '-1200px');
$(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);
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
{
$(io).remove();
$(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 io = $('#' + frameId);
var form = $('#' + formId);
$(form).attr('action', s.url);
$(form).attr('method', 'POST');
$(form).attr('target', frameId);
if(form.encoding)
{
form.encoding = 'multipart/form-data';
}
else
{
form.enctype = 'multipart/form-data';
}
$(form).submit();
} catch(e)
{
jQuery.handleError(s, xml, null, e);
}
if(window.attachEvent){
document.getElementById(frameId).attachEvent('onload', uploadCallback);
}
else{
document.getElementById(frameId).addEventListener('load', uploadCallback, false);
}
return {abort: function () {}};
},
uploadHttpData: function( r, type ) {
var data = !type;
data = type == "xml" || data ? r.responseXML : r.responseText;
// If the type is "script", eval it in global context
if ( type == "script" )
jQuery.globalEval( data );
// Get the JavaScript object, if JSON is used.
if ( type == "json" )
eval( "data = " + data );
// evaluate scripts within html
if ( type == "html" )
jQuery("<div>").html(data).evalScripts();
//alert($('param', data).each(function(){alert($(this).attr('value'));}));
return data;
}
})
三、纯iframe实现上传
upload.ashx
代码
//<%@ WebHandler Language="C#" Class="upload" %>
using System;
using System.Web;
public class upload : IHttpHandler {
private string Js(string v) {//此函数进行js的转义替换的，防止字符串中输入了'后造成回调输出的js中字符串不闭合
if (v == null) return "";
return v.Replace("'", @"\'");
}
//下面就是一个简单的示例，保存上传的文件，如果要验证上传的后缀名，得自己写，还有写数据库什么的
public void ProcessRequest (HttpContext context) {
HttpRequest Request = context.Request;
HttpResponse Response = context.Response;
HttpServerUtility Server = context.Server;
//指定输出头和编码
Response.ContentType = "text/html";
Response.Charset = "utf-8";
HttpPostedFile f = Request.Files["upfile"];//获取上传的文件
string des = Request.Form["des"]//获取描述
,newFileName=Guid.NewGuid().ToString();//使用guid生成新文件名
if (f.FileName == "")//未上传文件
Response.Write("<script>parent.UpdateMsg('','');</script>");//输出js，使用parent对象得到父页的引用
else { //保存文件
newFileName += System.IO.Path.GetExtension(f.FileName);//注意加上扩展名
try {
f.SaveAs(Server.MapPath("~/uploads/" + newFileName));//如果要保存到其他地方，注意修改这里
//调用父过程更新内容，注意要对des变量进行js转义替换，防止字符串不闭合提示错误
Response.Write("<script>parent.UpdateMsg('" +Js(des)+ "','" + newFileName + "')</script>");
}
catch {
Response.Write("<script>alert('保存文件失败！\\n请检查文件夹是否有写入权限！');</script>");//如果保存失败，输出js提示保存失败
}
}
}
public bool IsReusable {
get {
return false;
}
}
}
test.htm
代码
<!!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type" content="text/html;charset=utf-8" />
<title>使用隐藏的Iframe实现ajax无刷新上传</title>
</head>
<body>
<script type="text/javascript">
function UpdateMsg(des,filename){//此函数用来提供给提交到的页面如upload.ashx输出js的回调，更新当前页面的信息
if(filename==''){alert('未上传文件！');return false;}
document.getElementById('ajaxMsg').innerHTML='你在表单中输入的“文件描述”为：'+des+'<br/>'
+'上传的图片为：<a href="uploads/'+filename+'" target="_blank">'+filename+'</a>';
}
function check(f){
if(f.des.value==''){
alert('请输入文件描述！');f.des.focus();return false;
}
if(f.upfile.value==''){
alert('请选择文件！');f.upfile.focus();return false;
}
}
</script>
<!--隐藏的iframe来接受表单提交的信息-->
<iframe name="ajaxifr" style="display:none;"></iframe>
<!--这里设置target="ajaxifr"，这样表单就提交到iframe里面了，和平时未设置target属性时默认提交到当前页面-->
<!--注意一点的是使用iframe时在提交到的页面可以直接输出js来操作父页面的信息，一般的ajax提交文本信息时你需要返回信息，如果是js信息你还得eval下-->
<form method="post" enctype="multipart/form-data" action="upload.ashx" target="ajaxifr" onsubmit="return check(this)">
文件描述：<input type="text" name="des" /><br >
选择文件：<input type="file" name="upfile" /><br >
<input type="submit" value="提交" />
</form>
<!--放入此div用来实现上传的结果-->
<div id="ajaxMsg"></div>
</body>
</html>