there is a way to generate thrift description file for existing java classes using refletion? Avro has that feature, but i need to use thrift and i have a lot of existing business class in java that i need to serialize in c++ and java.
Not from the library directly; thrift generates it's own classes and some validation code so that both "ends" (client/server) can inter-operate without error. You should write code to map your business objects to thrift objects.