他のサンプルと同じにやると、なぜかClassCastExceptionが出たので一応掲載
●Mailet側
DefaultServiceManager dsm = (DefaultServiceManager) getMailetContext().getAttribute(Constants.AVALON_COMPONENT_MANAGER);
DataSourceSelector dss = (DataSourceSelector) dsm.lookup(DataSourceSelector.ROLE);
DataSourceComponent dsc = (DataSourceComponent) dss.select("OracleDB");