Importing from an .xlsx file via Rest API (Java)

I have a java application that processes raw data and turns it into a timesheet .xlsx file that is formatted properly so that it can be imported to our doctype “Timesheet”. It contains the employee ID, date, time in, and time out.

I can send each individual entry one by one but it takes forever. Is there a way to just upload the .xlsx file via HTTP so that the user would not have to upload it manually to the import section of the doc?

I also tried just dumping all the data in JSON and sending it in one POST, but it keeps returning 500 INTERNAL SERVER ERROR with TypeError: must be str, not ‘dict’.

Using Apache HTTP.