I have made a Spring Web flow application that uploads file using Multipart upload.
It works fine in case of normal form submits.

But in case of Asynchronous submit ,it is throwing exception:

Map key 'file' has value [HomeBackground.jpg] that is not of expected type [interface org.springframework.web.multipart.MultipartFile], instead it is of type [java.lang.String]

This exception comes when I try to retreive file into MultipartFile object of Spring.

I am using Ajax.Updator of prototype.js for async form submit.

Please help.