@Override
    public final void setOptionalService(OptionalService optionalService) {
        service = optionalService;
    }
for more detail, please access the super explanation.
@return null if you don't want to use SSORequestOperation; otherwise, a AppConn name is needed.
dss-standard/structure-standard/dss-structure-integration-standard/src/main/java/com/webank/wedatasphere/dss/standard/app/structure/optional/AbstractOptionalOperation.java