COPy command question

COPY tablename [ ( column [, ...] ) ]
    FROM { 'filename' | STDIN }
    [ [ WITH ] 
         .....
I want to migrate my tables from Oracle to Postgres. 
The COPY FROM command can take input from 'file' or 'STDIN'.
Is it possible for the COPY command to take its input from a
java program(which contains the oracle resultset) or any other way?

I know I could get the Oracle rows in a csv format but 
Im trying to get it done without any file in between ? 

In short is it possible to use this 'COPY' command to migrate my tables' 
data from Oracle to Postgresql without using any filein between?

Thanks
Sharmila