Java Project: Upload and Download file

I did the implementation but only one bug is needed to be fixed. I have also posted it in stackoverflow if you want to check in description then: https://stackoverflow.com/questions/69932364/xlsx-files-getting-corrupted-jdbc-file-upload-and-download

I want you to help me fixing this problem. When I download file and try to open it. I get error. I have attached it with this project.

I have other tasks also. For right now only this.