How to deal with Filemanager's upload action in the server-side script

I am using filemanager. There is no description in the document about upload action with filemanager, And I dont know what is the json value for request, and what json to return in the response. Please help with this, Thanks a lot

I’m dealing another bugs, the upload action request data is missing(no target, source etc.) while other actions such as copy, whose request data is received correctly.