jsp：

$('#myForm').ajaxSubmit({});

<form action="" name="myForm" id="myForm" method="post" enctype="multipart/form-data">
<input type="file" name="upload_file" id="upload_file" />
</form>

java：

@At
	@AdaptBy(type = UploadAdaptor.class, args = { "${app.root}/WEB-INF/tmp" })
	public String update(@Param("upload_file")TempFile f, HttpServletRequest request)

当选择文件时上传正常，不选择文件时有报错，报类转换异常，看下面回复图片