My question is How should i remain the file the user provide in second page?
If I understand what you are asking, and I'm not sure that I do, I don't think you can. The file is being uploaded as part of a multi-part request on the first submission. Deferring the processing of that file to a second request after a verification page is not possible since the uploaded file cannot be carried over to the subsequent request.
Is it not possible to change the manner in which you are conducting registration? It seems odd to me to upload a file prior to successfully
registering. I'd suggest making the file upload a second operation that the user completes
after the user id has been successfully validated.
hth,
bear