Oracle's sequence is very useful,we oftenly use it for most of my tables' primary key field,don't you ?

in my cmp ejb,the bean class name is "beana",and it's mapping table's name within oracle is "beana",thire primary field is "id". I also want use sequence's value for their primary key.in fact ,if i do not use sequence ,it will be very unconvient to operate my data in sqlplus or plsql.

how can i tell ejb container to use oracle's sequence when it creat every bean instance(mapping into new oracle record).