我用jquery.uploadfile做上传实例，代码如下：

var uploadObj = $("#fileuploader").uploadFile({
url:"http://up.qiniu.com/",
multiple:true,
autoSubmit:false,
fileName:"myfile",
formData: {"key":"<key>","token":"<mytoken>"},
maxFileCount:1,
showStatusAfterSuccess:false,
dragDropStr: "<span><b>拖放文件</b></span>",
abortStr:"放弃",
cancelStr:"终止",
doneStr:"OK",
multiDragErrorStr: "几个拖放文件是不允许的。",
extErrorStr:"不允许的扩展名",
sizeErrorStr:"不允许的大小",
uploadErrorStr:"禁止上传"
});
$("#startUpload").click(function()
{
    uploadObj.startUpload();
});

服务端错误是

{"error":"file is not specified in multipart"}