is it possible to automatically upload report on jasperserver?
Apparently not possible 'automatically' , but yes if you have an application in which you are using JasperServer as embedded application then yes you can have the upload, but yes there needs to be some sort of trigger, which initiates the upload.
Hope that this helps
If you're using Jaspersoft Studio, can't you just click on "Save"? It should ask if you want to upload the report to the server.
If you want to upload all reports in a directory, JasperReports Server has a web api to allow developers to write tools to upload files.