public class FooServiceImpl extends RemoteServiceServlet implements FooService {

    final Logger logger = LoggerFactory.getLogger(StockServiceImpl.class);

// ...
 @Override
 public String processCall(String payload) throws SerializationException {
   try {
    return super.processCall(payload);
   } catch (RuntimeException e) {
    logger.warn("Service Layer threw exception: ", e);
    // normally bad style but we need to throw again to inform the client
    throw e;
   }
 }
}