You can check reference-ril.c, ril.cpp & rild.c for complete flow.
You can put your own debug statements and then try to understand the
complete flow, i also followed the same path. :)
On java front no need to worry too much, you can assume that they are stable
and they juts try to connect to the rild sockets on which they can send their
requests & recieved URC's from teh baseband via ril layer.