How to Transfer data using BAPI from NON SAP system

How to transfer the data using BAPI from NON - SAP syetm to SAP.

I know, how to do it from a flat file. Can any one explain me with an example or any kind of proper explonation will do.

How can we transfer data from non sap systems like another software(JAVA, .Asp)----> to BAPI

Any help will be appreciated!

Ragrds,

Krishna Chaitanya