I solved this issue.. using trident just you have to use modified field name in list of input fields. For example :-
topology.newStream("dummySpout",new DummySpout()).stateQuery(tridentState, new QueryFunctionClass(), new Fields("outLpi","outFileId"))
.each(new Fields("outLpi"),new DBReaderFunction((ArrayList<String>)conf.get("listOfFields")), new Fields((ArrayList<String>)conf.get("listOfFields")))
.each(new Fields((ArrayList<String>)conf.get("listOfFields")), new LoggerFilter())
.aggregate(new Fields("SAL"), new ApplyAggregator(),new Fields("sum"))
.each(new Fields("sum","SAL"),new LoggerFilter());
in last line "sum" is the modified field and SAL is original field.